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$I�'��$I���'I�$I�$I�$I�$I�$I�'In�m�۶m۶m��۶m۶m�6n�=~����m��m�m� =�� �� X HELP_DATEThis help information was generated from the MariaDB Knowledge Base
on 2 September 2019. ` 2 AREAA synonym for ST_AREA.
URL: https://mariadb.com/kb/en/polygon-properties-area/https://mariadb.com/kb/en/polygon-properties-area/ U # CENTROIDA synonym for ST_CENTROID.
URL: https://mariadb.com/kb/en/centroid/https://mariadb.com/kb/en/centroid/ p : ExteriorRingA synonym for ST_ExteriorRing.
URL:
https://mariadb.com/kb/en/polygon-properties-exteriorring/https://mariadb.com/kb/en/polygon-properties-exteriorring/
r ; InteriorRingNA synonym for ST_InteriorRingN.
URL:
https://mariadb.com/kb/en/polygon-properties-interiorringn/https://mariadb.com/kb/en/polygon-properties-interiorringn/ x > NumInteriorRingsA synonym for ST_NumInteriorRings.
URL:
https://mariadb.com/kb/en/polygon-properties-numinteriorrings/https://mariadb.com/kb/en/polygon-properties-numinteriorrings/
" ST_AREASyntax
------
ST_Area(poly)
Area(poly)
Description
-----------
Returns as a double-precision number the area of the Polygon
value poly, as measured in its spatial reference system.
ST_Area() and Area() are synonyms.
Examples
--------
SET @poly = 'Polygon((0 0,0 3,3 0,0 0),(1 1,1 2,2 1,1
1))';
SELECT Area(GeomFromText(@poly));
+---------------------------+
| Area(GeomFromText(@poly)) |
+---------------------------+
| 4 |
+---------------------------+
URL: https://mariadb.com/kb/en/st_area/https://mariadb.com/kb/en/st_area/ 6& ST_CENTROIDSyntax
------
ST_Centroid(mpoly)
Centroid(mpoly)
Description
-----------
Returns a point reflecting the mathematical centroid
(geometric center) for the MultiPolygon mpoly. The resulting
point will not necessarily be on the MultiPolygon.
ST_Centroid() and Centroid() are synonyms.
Examples
--------
SET @poly = ST_GeomFromText('POLYGON((0 0,20 0,20 20,0 20,0
0))');
SELECT ST_AsText(ST_Centroid(@poly)) AS center;
+--------------+
| center |
+--------------+
| POINT(10 10) |
+--------------+
URL: https://mariadb.com/kb/en/st_centroid/https://mariadb.com/kb/en/st_centroid/ w* ST_ExteriorRingSyntax
------
ST_ExteriorRing(poly)
ExteriorRing(poly)
Description
-----------
Returns the exterior ring of the Polygon value poly as a
LineString.
ST_ExteriorRing() and ExteriorRing() are synonyms.
Examples
--------
SET @poly = 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2
1,1 1))';
SELECT AsText(ExteriorRing(GeomFromText(@poly)));
+-------------------------------------------+
| AsText(ExteriorRing(GeomFromText(@poly))) |
+-------------------------------------------+
| LINESTRING(0 0,0 3,3 3,3 0,0 0) |
+-------------------------------------------+
URL: https://mariadb.com/kb/en/st_exteriorring/https://mariadb.com/kb/en/st_exteriorring/
�+ ST_InteriorRingNSyntax
------
ST_InteriorRingN(poly,N)
InteriorRingN(poly,N)
Description
-----------
Returns the N-th interior ring for the Polygon value poly as
a LineString. Rings are numbered beginning with 1.
ST_InteriorRingN() and InteriorRingN() are synonyms.
Examples
--------
SET @poly = 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2
1,1 1))';
SELECT AsText(InteriorRingN(GeomFromText(@poly),1));
+----------------------------------------------+
| AsText(InteriorRingN(GeomFromText(@poly),1)) |
+----------------------------------------------+
| LINESTRING(1 1,1 2,2 2,2 1,1 1) |
+----------------------------------------------+
URL: https://mariadb.com/kb/en/st_interiorringn/https://mariadb.com/kb/en/st_interiorringn/ �. ST_NumInteriorRingsSyntax
------
ST_NumInteriorRings(poly)
NumInteriorRings(poly)
Description
-----------
Returns an integer containing the number of interior rings
in the Polygon value poly.
Note that according the the OpenGIS standard, a POLYGON
should have exactly one ExteriorRing and all other rings
should lie within that ExteriorRing and thus be the
InteriorRings. Practically, however, some systems, including
MariaDB's, permit polygons to have several
'ExteriorRings'. In the case of there being multiple,
non-overlapping exterior rings ST_NumInteriorRings() will
return 1.
ST_NumInteriorRings() and NumInteriorRings() are synonyms.
Examples
--------
SET @poly = 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2
1,1 1))';
SELECT NumInteriorRings(GeomFromText(@poly));
+---------------------------------------+
| NumInteriorRings(GeomFromText(@poly)) |
+---------------------------------------+
| 1 |
+---------------------------------------+
Non-overlapping 'polygon':
SELECT ST_NumInteriorRings(ST_PolyFromText('POLYGON((0 0,10
0,10 10,0 10,0 0),
(-1 -1,-5 -1,-5 -5,-1 -5,-1 -1))')) AS NumInteriorRings;
+------------------+
| NumInteriorRings |
+------------------+
| 1 |
+------------------+
URL: https://mariadb.com/kb/en/st_numinteriorrings/https://mariadb.com/kb/en/st_numinteriorrings/ |) WKT DefinitionDescription
-----------
The Well-Known Text (WKT) representation of Geometry is
designed to exchange geometry data in ASCII form. Examples
of the basic geometry types include:
Geometry Types |
POINT |
LINESTRING |
POLYGON |
MULTIPOINT |
MULTILINESTRING |
MULTIPOLYGON |
GEOMETRYCOLLECTION |
GEOMETRY |
URL: https://mariadb.com/kb/en/wkt-definition/https://mariadb.com/kb/en/wkt-definition/
W % AsTextA synonym for ST_AsText().
URL: https://mariadb.com/kb/en/wkt-astext/https://mariadb.com/kb/en/wkt-astext/ V $ AsWKTA synonym for ST_AsText().
URL: https://mariadb.com/kb/en/wkt-aswkt/https://mariadb.com/kb/en/wkt-aswkt/ i / GeomCollFromTextA synonym for ST_GeomCollFromText.
URL: https://mariadb.com/kb/en/wkt-geomcollfromtext/https://mariadb.com/kb/en/wkt-geomcollfromtext/ o 5 GeometryCollectionFromTextA synonym for ST_GeomCollFromText.
URL: https://mariadb.com/kb/en/geometrycollectionfromtext/https://mariadb.com/kb/en/geometrycollectionfromtext/ a + GeometryFromTextA synonym for ST_GeomFromText.
URL: https://mariadb.com/kb/en/geometryfromtext/https://mariadb.com/kb/en/geometryfromtext/ a + GeomFromTextA synonym for ST_GeomFromText.
URL: https://mariadb.com/kb/en/wkt-geomfromtext/https://mariadb.com/kb/en/wkt-geomfromtext/ a + LineFromTextA synonym for ST_LineFromText.
URL: https://mariadb.com/kb/en/wkt-linefromtext/https://mariadb.com/kb/en/wkt-linefromtext/ c - LineStringFromTextA synonym for ST_LineFromText.
URL: https://mariadb.com/kb/en/linestringfromtext/https://mariadb.com/kb/en/linestringfromtext/
�( MLineFromTextSyntax
------
MLineFromText(wkt[,srid])
MultiLineStringFromText(wkt[,srid])
Description
-----------
Constructs a MULTILINESTRING value using its WKT
representation and SRID.
MLineFromText() and MultiLineStringFromText() are synonyms.
Examples
--------
CREATE TABLE gis_multi_line (g MULTILINESTRING);
SHOW FIELDS FROM gis_multi_line;
INSERT INTO gis_multi_line VALUES
(MultiLineStringFromText('MULTILINESTRING((10 48,10 21,10
0),(16 0,16 23,16 48))')),
(MLineFromText('MULTILINESTRING((10 48,10 21,10 0))')),
(MLineFromWKB(AsWKB(MultiLineString(LineString(Point(1, 2),
Point(3, 5)), LineString(Point(2, 5), Point(5, 8), Point(21,
7))))));
URL: https://mariadb.com/kb/en/mlinefromtext/https://mariadb.com/kb/en/mlinefromtext/ � � x� �� (� \� �� � �� ���F ��Lu A7� o� �� � y � m ��� � `) MPointFromTextSyntax
------
MPointFromText(wkt[,srid])
MultiPointFromText(wkt[,srid])
Description
-----------
Constructs a MULTIPOINT value using its WKT representation
and SRID.
MPointFromText() and MultiPointFromText() are synonyms.
Examples
--------
CREATE TABLE gis_multi_point (g MULTIPOINT);
SHOW FIELDS FROM gis_multi_point;
INSERT INTO gis_multi_point VALUES
(MultiPointFromText('MULTIPOINT(0 0,10 10,10 20,20
20)')),
(MPointFromText('MULTIPOINT(1 1,11 11,11 21,21 21)')),
(MPointFromWKB(AsWKB(MultiPoint(Point(3, 6), Point(4,
10)))));
URL: https://mariadb.com/kb/en/mpointfromtext/https://mariadb.com/kb/en/mpointfromtext/
3( MPolyFromTextSyntax
------
MPolyFromText(wkt[,srid])
MultiPolygonFromText(wkt[,srid])
Description
-----------
Constructs a MULTIPOLYGON value using its WKT representation
and SRID.
MPolyFromText() and MultiPolygonFromText() are synonyms.
Examples
--------
CREATE TABLE gis_multi_polygon (g MULTIPOLYGON);
SHOW FIELDS FROM gis_multi_polygon;
INSERT INTO gis_multi_polygon VALUES
(MultiPolygonFromText('MULTIPOLYGON(((28 26,28 0,84 0,84
42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67
13,59 13,59 18)))')),
(MPolyFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28
26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59
13,59 18)))')),
(MPolyFromWKB(AsWKB(MultiPolygon(Polygon(LineString(Point(0,
3), Point(3, 3), Point(3, 0), Point(0, 3)))))));
URL: https://mariadb.com/kb/en/mpolyfromtext/https://mariadb.com/kb/en/mpolyfromtext/ f 2 MultiLineStringFromTextA synonym for MLineFromText.
URL: https://mariadb.com/kb/en/multilinestringfromtext/https://mariadb.com/kb/en/multilinestringfromtext/ b - MultiPointFromTextA synonym for MPointFromText.
URL: https://mariadb.com/kb/en/multipointfromtext/https://mariadb.com/kb/en/multipointfromtext/ c / MultiPolygonFromTextA synonym for MPolyFromText.
URL: https://mariadb.com/kb/en/multipolygonfromtext/https://mariadb.com/kb/en/multipolygonfromtext/
c , PointFromTextA synonym for ST_PointFromText.
URL: https://mariadb.com/kb/en/wkt-pointfromtext/https://mariadb.com/kb/en/wkt-pointfromtext/ a + PolyFromTextA synonym for ST_PolyFromText.
URL: https://mariadb.com/kb/en/wkt-polyfromtext/https://mariadb.com/kb/en/wkt-polyfromtext/ ` * PolygonFromTextA synonym for ST_PolyFromText.
URL: https://mariadb.com/kb/en/polygonfromtext/https://mariadb.com/kb/en/polygonfromtext/ C$ ST_AsTextSyntax
------
ST_AsText(g)
AsText(g)
ST_AsWKT(g)
AsWKT(g)
Description
-----------
Converts a value in internal geometry format to its WKT
representation and returns the string result.
ST_AsText(), AsText(), ST_AsWKT() and AsWKT() are all
synonyms.
Examples
--------
SET @g = 'LineString(1 1,4 4,6 6)';
SELECT ST_AsText(ST_GeomFromText(@g));
+--------------------------------+
| ST_AsText(ST_GeomFromText(@g)) |
+--------------------------------+
| LINESTRING(1 1,4 4,6 6) |
+--------------------------------+
URL: https://mariadb.com/kb/en/st_astext/https://mariadb.com/kb/en/st_astext/ U # ST_ASWKTA synonym for ST_ASTEXT().
URL: https://mariadb.com/kb/en/st_aswkt/https://mariadb.com/kb/en/st_aswkt/ o. ST_GeomCollFromTextSyntax
------
ST_GeomCollFromText(wkt[,srid])
ST_GeometryCollectionFromText(wkt[,srid])
GeomCollFromText(wkt[,srid])
GeometryCollectionFromText(wkt[,srid])
Description
-----------
Constructs a GEOMETRYCOLLECTION value using its WKT
representation and SRID.
ST_GeomCollFromText(), ST_GeometryCollectionFromText(),
GeomCollFromText() and GeometryCollectionFromText() are all
synonyms.
Example
CREATE TABLE gis_geometrycollection (g GEOMETRYCOLLECTION);
SHOW FIELDS FROM gis_geometrycollection;
INSERT INTO gis_geometrycollection VALUES
(GeomCollFromText('GEOMETRYCOLLECTION(POINT(0 0),
LINESTRING(0 0,10 10))')),
(GeometryFromWKB(AsWKB(GeometryCollection(Point(44, 6),
LineString(Point(3, 6), Point(7, 9)))))),
(GeomFromText('GeometryCollection()')),
(GeomFromText('GeometryCollection EMPTY'));
URL: https://mariadb.com/kb/en/st_geomcollfromtext/https://mariadb.com/kb/en/st_geomcollfromtext/ ! r 8 ST_GeometryCollectionFromTextA synonym for ST_GeomCollFromText.
URL:
https://mariadb.com/kb/en/st_geometrycollectionfromtext/https://mariadb.com/kb/en/st_geometrycollectionfromtext/ " d . ST_GeometryFromTextA synonym for ST_GeomFromText.
URL: https://mariadb.com/kb/en/st_geometryfromtext/https://mariadb.com/kb/en/st_geometryfromtext/ # �* ST_GeomFromTextSyntax
------
ST_GeomFromText(wkt[,srid])
ST_GeometryFromText(wkt[,srid])
GeomFromText(wkt[,srid])
GeometryFromText(wkt[,srid])
Description
-----------
Constructs a geometry value of any type using its WKT
representation and SRID.
GeomFromText(), GeometryFromText(), ST_GeomFromText() and
ST_GeometryFromText() are all synonyms.
Example
SET @g = ST_GEOMFROMTEXT('POLYGON((1 1,1 5,4 9,6 9,9 3,7
2,1 1))');
URL: https://mariadb.com/kb/en/st_geomfromtext/https://mariadb.com/kb/en/st_geomfromtext/ $ �* ST_LineFromTextSyntax
------
ST_LineFromText(wkt[,srid])
ST_LineStringFromText(wkt[,srid])
LineFromText(wkt[,srid])
LineStringFromText(wkt[,srid])
Description
-----------
Constructs a LINESTRING value using its WKT representation
and SRID.
ST_LineFromText(), ST_LineStringFromText(),
ST_LineFromText() and ST_LineStringFromText() are all
synonyms.
Examples
--------
CREATE TABLE gis_line (g LINESTRING);
SHOW FIELDS FROM gis_line;
INSERT INTO gis_line VALUES
(LineFromText('LINESTRING(0 0,0 10,10 0)')),
(LineStringFromText('LINESTRING(10 10,20 10,20 20,10 20,10
10)')),
(LineStringFromWKB(AsWKB(LineString(Point(10, 10),
Point(40, 10)))));
URL: https://mariadb.com/kb/en/st_linefromtext/https://mariadb.com/kb/en/st_linefromtext/ % f 0 ST_LineStringFromTextA synonym for ST_LineFromText.
URL: https://mariadb.com/kb/en/st_linestringfromtext/https://mariadb.com/kb/en/st_linestringfromtext/ & )+ ST_PointFromTextSyntax
------
ST_PointFromText(wkt[,srid])
PointFromText(wkt[,srid])
Description
-----------
Constructs a POINT value using its WKT representation and
SRID.
ST_PointFromText() and PointFromText() are synonyms.
Examples
--------
CREATE TABLE gis_point (g POINT);
SHOW FIELDS FROM gis_point;
INSERT INTO gis_point VALUES
(PointFromText('POINT(10 10)')),
(PointFromText('POINT(20 10)')),
(PointFromText('POINT(20 20)')),
(PointFromWKB(AsWKB(PointFromText('POINT(10 20)'))));
URL: https://mariadb.com/kb/en/st_pointfromtext/https://mariadb.com/kb/en/st_pointfromtext/ ' t* ST_PolyFromTextSyntax
------
ST_PolyFromText(wkt[,srid])
ST_PolygonFromText(wkt[,srid])
PolyFromText(wkt[,srid])
PolygonFromText(wkt[,srid])
Description
-----------
Constructs a POLYGON value using its WKT representation and
SRID.
ST_PolyFromText(), ST_PolygonFromText(), PolyFromText() and
ST_PolygonFromText() are all synonyms.
Examples
--------
CREATE TABLE gis_polygon (g POLYGON);
INSERT INTO gis_polygon VALUES
(PolygonFromText('POLYGON((10 10,20 10,20 20,10 20,10
10))')),
(PolyFromText('POLYGON((0 0,50 0,50 50,0 50,0 0), (10
10,20 10,20 20,10 20,10 10))'));
URL: https://mariadb.com/kb/en/st_polyfromtext/https://mariadb.com/kb/en/st_polyfromtext/ ��xr�� ��'�� � J
�� � >
~� � �� G� �� �� '� �v ��Ê �� ( c - ST_PolygonFromTextA synonym for ST_PolyFromText.
URL: https://mariadb.com/kb/en/st_polygonfromtext/https://mariadb.com/kb/en/st_polygonfromtext/ ) �, Addition Operator (+)Syntax
------
+
Description
-----------
Addition.
If both operands are integers, the result is calculated with
BIGINT precision. If either integer is unsigned, the result
is also an unsigned integer.
For real or string operands, the operand with the highest
precision determines the result precision.
Examples
--------
SELECT 3+5;
+-----+
| 3+5 |
+-----+
| 8 |
+-----+
URL: https://mariadb.com/kb/en/addition-operator/https://mariadb.com/kb/en/addition-operator/ * d0 Subtraction Operator (-)Syntax
------
-
Description
-----------
Subtraction. The operator is also used as the unary minus
for changing sign.
If both operands are integers, the result is calculated with
BIGINT precision. If either integer is unsigned, the result
is also an unsigned integer, unless the
NO_UNSIGNED_SUBTRACTION SQL_MODE is enabled, in which case
the result is always signed.
For real or string operands, the operand with the highest
precision determines the result precision.
Examples
--------
SELECT 96-9;
+------+
| 96-9 |
+------+
| 87 |
+------+
SELECT 15-17;
+-------+
| 15-17 |
+-------+
| -2 |
+-------+
SELECT 3.66 + 1.333;
+--------------+
| 3.66 + 1.333 |
+--------------+
| 4.993 |
+--------------+
Unary minus:
SELECT - (3+5);
+---------+
| - (3+5) |
+---------+
| -8 |
+---------+
URL: https://mariadb.com/kb/en/subtraction-operator-/https://mariadb.com/kb/en/subtraction-operator-/ + , Division Operator (/)Syntax
------
/
Description
-----------
Division operator. Dividing by zero will return NULL. By
default, returns four digits after the decimal. This is
determined by the server system variable
div_precision_increment which by default is four. It can be
set from 0 to 30.
Dividing by zero returns NULL. If the
ERROR_ON_DIVISION_BY_ZERO SQL_MODE is used (the default
since MariaDB 10.2.4), a division by zero also produces a
warning.
Examples
--------
SELECT 4/5;
+--------+
| 4/5 |
+--------+
| 0.8000 |
+--------+
SELECT 300/(2-2);
+-----------+
| 300/(2-2) |
+-----------+
| NULL |
+-----------+
SELECT 300/7;
+---------+
| 300/7 |
+---------+
| 42.8571 |
+---------+
Changing div_precision_increment for the session from the
default of four to six:
SET div_precision_increment = 6;
SELECT 300/7;
+-----------+
| 300/7 |
+-----------+
| 42.857143 |
+-----------+
SELECT 300/7;
+-----------+
| 300/7 |
+-----------+
| 42.857143 |
+-----------+
URL: https://mariadb.com/kb/en/division-operator/https://mariadb.com/kb/en/division-operator/ , E2 Multiplication Operator (*)Syntax
------
*
Description
-----------
Multiplication operator.
Examples
--------
SELECT 7*6;
+-----+
| 7*6 |
+-----+
| 42 |
+-----+
SELECT 1234567890*9876543210;
+-----------------------+
| 1234567890*9876543210 |
+-----------------------+
| -6253480962446024716 |
+-----------------------+
SELECT 18014398509481984*18014398509481984.0;
+---------------------------------------+
| 18014398509481984*18014398509481984.0 |
+---------------------------------------+
| 324518553658426726783156020576256.0 |
+---------------------------------------+
SELECT 18014398509481984*18014398509481984;
+-------------------------------------+
| 18014398509481984*18014398509481984 |
+-------------------------------------+
| 0 |
+-------------------------------------+
URL: https://mariadb.com/kb/en/multiplication-operator/https://mariadb.com/kb/en/multiplication-operator/ - !* Modulo Operator (%)Syntax
------
N % M
Description
-----------
Modulo operator. Returns the remainder of N divided by M.
See also MOD.
Examples
--------
SELECT 1042 % 50;
+-----------+
| 1042 % 50 |
+-----------+
| 42 |
+-----------+
URL: https://mariadb.com/kb/en/modulo-operator/https://mariadb.com/kb/en/modulo-operator/ . t DIVSyntax
------
DIV
Description
-----------
Integer division. Similar to FLOOR(), but is safe with
BIGINT values.
Incorrect results may occur for non-integer operands that
exceed BIGINT range.
If the ERROR_ON_DIVISION_BY_ZERO SQL_MODE is used, a
division by zero produces an error. Otherwise, it returns
NULL.
The remainder of a division can be obtained using the MOD
operator.
Examples
--------
SELECT 300 DIV 7;
+-----------+
| 300 DIV 7 |
+-----------+
| 42 |
+-----------+
SELECT 300 DIV 0;
+-----------+
| 300 DIV 0 |
+-----------+
| NULL |
+-----------+
URL: https://mariadb.com/kb/en/div/https://mariadb.com/kb/en/div/ / ABSSyntax
------
ABS(X)
Description
-----------
Returns the absolute (non-negative) value of X. If X is not
a number, it is converted to a numeric type.
Examples
--------
SELECT ABS(42);
+---------+
| ABS(42) |
+---------+
| 42 |
+---------+
SELECT ABS(-42);
+----------+
| ABS(-42) |
+----------+
| 42 |
+----------+
SELECT ABS(DATE '1994-01-01');
+------------------------+
| ABS(DATE '1994-01-01') |
+------------------------+
| 19940101 |
+------------------------+
URL: https://mariadb.com/kb/en/abs/https://mariadb.com/kb/en/abs/ 0 � ACOSSyntax
------
ACOS(X)
Description
-----------
Returns the arc cosine of X, that is, the value whose cosine
is X.
Returns NULL if X is not in the range -1 to 1.
Examples
--------
SELECT ACOS(1);
+---------+
| ACOS(1) |
+---------+
| 0 |
+---------+
SELECT ACOS(1.0001);
+--------------+
| ACOS(1.0001) |
+--------------+
| NULL |
+--------------+
SELECT ACOS(0);
+-----------------+
| ACOS(0) |
+-----------------+
| 1.5707963267949 |
+-----------------+
SELECT ACOS(0.234);
+------------------+
| ACOS(0.234) |
+------------------+
| 1.33460644244679 |
+------------------+
URL: https://mariadb.com/kb/en/acos/https://mariadb.com/kb/en/acos/ 1 � ASINSyntax
------
ASIN(X)
Description
-----------
Returns the arc sine of X, that is, the value whose sine is
X. Returns
NULL if X is not in the range -1 to 1.
Examples
--------
SELECT ASIN(0.2);
+--------------------+
| ASIN(0.2) |
+--------------------+
| 0.2013579207903308 |
+--------------------+
SELECT ASIN('foo');
+-------------+
| ASIN('foo') |
+-------------+
| 0 |
+-------------+
SHOW WARNINGS;
+---------+------+-----------------------------------------+
| Level | Code | Message |
+---------+------+-----------------------------------------+
| Warning | 1292 | Truncated incorrect DOUBLE value: 'foo'
|
+---------+------+-----------------------------------------+
URL: https://mariadb.com/kb/en/asin/https://mariadb.com/kb/en/asin/ 2 � ATANSyntax
------
ATAN(X)
Description
-----------
Returns the arc tangent of X, that is, the value whose
tangent is X.
Examples
--------
SELECT ATAN(2);
+--------------------+
| ATAN(2) |
+--------------------+
| 1.1071487177940904 |
+--------------------+
SELECT ATAN(-2);
+---------------------+
| ATAN(-2) |
+---------------------+
| -1.1071487177940904 |
+---------------------+
URL: https://mariadb.com/kb/en/atan/https://mariadb.com/kb/en/atan/ 3 [ ATAN2Syntax
------
ATAN(Y,X), ATAN2(Y,X)
Description
-----------
Returns the arc tangent of the two variables X and Y. It is
similar to
calculating the arc tangent of Y / X, except that the signs
of both
arguments are used to determine the quadrant of the result.
Examples
--------
SELECT ATAN(-2,2);
+---------------------+
| ATAN(-2,2) |
+---------------------+
| -0.7853981633974483 |
+---------------------+
SELECT ATAN2(PI(),0);
+--------------------+
| ATAN2(PI(),0) |
+--------------------+
| 1.5707963267948966 |
+--------------------+
URL: https://mariadb.com/kb/en/atan2/https://mariadb.com/kb/en/atan2/ ` �u�_��y4��jl�
�xR��� � w�m �� 4 � CEILSyntax
------
CEIL(X)
Description
-----------
CEIL() is a synonym for CEILING().
URL: https://mariadb.com/kb/en/ceil/https://mariadb.com/kb/en/ceil/ 5 �" CEILINGSyntax
------
CEILING(X)
Description
-----------
Returns the smallest integer value not less than X.
Examples
--------
SELECT CEILING(1.23);
+---------------+
| CEILING(1.23) |
+---------------+
| 2 |
+---------------+
SELECT CEILING(-1.23);
+----------------+
| CEILING(-1.23) |
+----------------+
| -1 |
+----------------+
URL: https://mariadb.com/kb/en/ceiling/https://mariadb.com/kb/en/ceiling/ 6 L CONVSyntax
------
CONV(N,from_base,to_base)
Description
-----------
Converts numbers between different number bases. Returns a
string
representation of the number N, converted from base
from_base
to base to_base.
Returns NULL if any argument is NULL, or if the second or
third argument are not in the allowed range.
The argument N is interpreted as an integer, but may be
specified as an
integer or a string. The minimum base is 2 and the maximum
base is 36. If
to_base is a negative number, N is regarded as a signed
number.
Otherwise, N is treated as unsigned. CONV() works with
64-bit
precision.
Some shortcuts for this function are also available: BIN(),
OCT(), HEX(), UNHEX(). Also, MariaDB allows binary literal
values and hexadecimal literal values.
Examples
--------
SELECT CONV('a',16,2);
+----------------+
| CONV('a',16,2) |
+----------------+
| 1010 |
+----------------+
SELECT CONV('6E',18,8);
+-----------------+
| CONV('6E',18,8) |
+-----------------+
| 172 |
+-----------------+
SELECT CONV(-17,10,-18);
+------------------+
| CONV(-17,10,-18) |
+------------------+
| -H |
+------------------+
SELECT CONV(12+'10'+'10'+0xa,10,10);
+------------------------------+
| CONV(12+'10'+'10'+0xa,10,10) |
+------------------------------+
| 42 |
+------------------------------+
URL: https://mariadb.com/kb/en/conv/https://mariadb.com/kb/en/conv/ 7 COSSyntax
------
COS(X)
Description
-----------
Returns the cosine of X, where X is given in radians.
Examples
--------
SELECT COS(PI());
+-----------+
| COS(PI()) |
+-----------+
| -1 |
+-----------
URL: https://mariadb.com/kb/en/cos/https://mariadb.com/kb/en/cos/ 8 � COTSyntax
------
COT(X)
Description
-----------
Returns the cotangent of X.
Examples
--------
SELECT COT(42);
+--------------------+
| COT(42) |
+--------------------+
| 0.4364167060752729 |
+--------------------+
SELECT COT(12);
+---------------------+
| COT(12) |
+---------------------+
| -1.5726734063976893 |
+---------------------+
SELECT COT(0);
ERROR 1690 (22003): DOUBLE value is out of range in
'cot(0)'
URL: https://mariadb.com/kb/en/cot/https://mariadb.com/kb/en/cot/ 9 P CRC32Syntax
------
CRC32(expr)
Description
-----------
Computes a cyclic redundancy check value and returns a
32-bit unsigned
value. The result is NULL if the argument is NULL. The
argument is
expected to be a string and (if possible) is treated as one
if it is
not.
Examples
--------
SELECT CRC32('MariaDB');
+------------------+
| CRC32('MariaDB') |
+------------------+
| 4227209140 |
+------------------+
SELECT CRC32('mariadb');
+------------------+
| CRC32('mariadb') |
+------------------+
| 2594253378 |
+------------------+
URL: https://mariadb.com/kb/en/crc32/https://mariadb.com/kb/en/crc32/ : G" DEGREESSyntax
------
DEGREES(X)
Description
-----------
Returns the argument X, converted from radians to degrees.
This is the converse of the RADIANS() function.
Examples
--------
SELECT DEGREES(PI());
+---------------+
| DEGREES(PI()) |
+---------------+
| 180 |
+---------------+
SELECT DEGREES(PI() / 2);
+-------------------+
| DEGREES(PI() / 2) |
+-------------------+
| 90 |
+-------------------+
SELECT DEGREES(45);
+-----------------+
| DEGREES(45) |
+-----------------+
| 2578.3100780887 |
+-----------------+
URL: https://mariadb.com/kb/en/degrees/https://mariadb.com/kb/en/degrees/ ; � EXPSyntax
------
EXP(X)
Description
-----------
Returns the value of e (the base of natural logarithms)
raised to the
power of X. The inverse of this function is LOG() (using a
single
argument only) or LN().
If X is NULL, this function returns NULL.
Examples
--------
SELECT EXP(2);
+------------------+
| EXP(2) |
+------------------+
| 7.38905609893065 |
+------------------+
SELECT EXP(-2);
+--------------------+
| EXP(-2) |
+--------------------+
| 0.1353352832366127 |
+--------------------+
SELECT EXP(0);
+--------+
| EXP(0) |
+--------+
| 1 |
+--------+
SELECT EXP(NULL);
+-----------+
| EXP(NULL) |
+-----------+
| NULL |
+-----------+
URL: https://mariadb.com/kb/en/exp/https://mariadb.com/kb/en/exp/ < q FLOORSyntax
------
FLOOR(X)
Description
-----------
Returns the largest integer value not greater than X.
Examples
--------
SELECT FLOOR(1.23);
+-------------+
| FLOOR(1.23) |
+-------------+
| 1 |
+-------------+
SELECT FLOOR(-1.23);
+--------------+
| FLOOR(-1.23) |
+--------------+
| -2 |
+--------------+
URL: https://mariadb.com/kb/en/floor/https://mariadb.com/kb/en/floor/ = � LNSyntax
------
LN(X)
Description
-----------
Returns the natural logarithm of X; that is, the base-e
logarithm of X.
If X is less than or equal to 0, or NULL, then NULL is
returned.
The inverse of this function is EXP().
Examples
--------
SELECT LN(2);
+-------------------+
| LN(2) |
+-------------------+
| 0.693147180559945 |
+-------------------+
SELECT LN(-2);
+--------+
| LN(-2) |
+--------+
| NULL |
+--------+
URL: https://mariadb.com/kb/en/ln/https://mariadb.com/kb/en/ln/ > > LOGSyntax
------
LOG(X), LOG(B,X)
Description
-----------
If called with one parameter, this function returns the
natural
logarithm of X. If X is less than or equal to 0, then NULL
is
returned.
If called with two parameters, it returns the logarithm of X
to the base B. If B is
URL: https://mariadb.com/kb/en/log/https://mariadb.com/kb/en/log/ ? � LOG10Syntax
------
LOG10(X)
Description
-----------
Returns the base-10 logarithm of X.
Examples
--------
SELECT LOG10(2);
+-------------------+
| LOG10(2) |
+-------------------+
| 0.301029995663981 |
+-------------------+
SELECT LOG10(100);
+------------+
| LOG10(100) |
+------------+
| 2 |
+------------+
SELECT LOG10(-100);
+-------------+
| LOG10(-100) |
+-------------+
| NULL |
+-------------+
URL: https://mariadb.com/kb/en/log10/https://mariadb.com/kb/en/log10/ @ � LOG2Syntax
------
LOG2(X)
Description
-----------
Returns the base-2 logarithm of X.
Examples
--------
SELECT LOG2(4398046511104);
+---------------------+
| LOG2(4398046511104) |
+---------------------+
| 42 |
+---------------------+
SELECT LOG2(65536);
+-------------+
| LOG2(65536) |
+-------------+
| 16 |
+-------------+
SELECT LOG2(-100);
+------------+
| LOG2(-100) |
+------------+
| NULL |
+------------+
URL: https://mariadb.com/kb/en/log2/https://mariadb.com/kb/en/log2/ B � OCTSyntax
------
OCT(N)
Description
-----------
Returns a string representation of the octal value of N,
where N is a longlong (BIGINT) number. This is equivalent to
CONV(N,10,8). Returns NULL if N is NULL.
Examples
--------
SELECT OCT(34);
+---------+
| OCT(34) |
+---------+
| 42 |
+---------+
SELECT OCT(12);
+---------+
| OCT(12) |
+---------+
| 14 |
+---------+
URL: https://mariadb.com/kb/en/oct/https://mariadb.com/kb/en/oct/ ` �U S�m�4�>��
~= �3
0�}� � � �44� �� A 9 MODSyntax
------
MOD(N,M), N % M, N MOD M
Description
-----------
Modulo operation. Returns the remainder of N divided by M.
See also Modulo Operator.
If the ERROR_ON_DIVISION_BY_ZERO SQL_MODE is used, any
number modulus zero produces an error. Otherwise, it returns
NULL.
The integer part of a division can be obtained using DIV.
Examples
--------
SELECT 1042 % 50;
+-----------+
| 1042 % 50 |
+-----------+
| 42 |
+-----------+
SELECT MOD(234, 10);
+--------------+
| MOD(234, 10) |
+--------------+
| 4 |
+--------------+
SELECT 253 % 7;
+---------+
| 253 % 7 |
+---------+
| 1 |
+---------+
SELECT MOD(29,9);
+-----------+
| MOD(29,9) |
+-----------+
| 2 |
+-----------+
SELECT 29 MOD 9;
+----------+
| 29 MOD 9 |
+----------+
| 2 |
+----------+
URL: https://mariadb.com/kb/en/mod/https://mariadb.com/kb/en/mod/ C # PISyntax
------
PI()
Description
-----------
Returns the value of π (pi). The default number of decimal
places
displayed is six, but MariaDB uses the full double-precision
value
internally.
Examples
--------
SELECT PI();
+----------+
| PI() |
+----------+
| 3.141593 |
+----------+
SELECT PI()+0.0000000000000000000000;
+-------------------------------+
| PI()+0.0000000000000000000000 |
+-------------------------------+
| 3.1415926535897931159980 |
+-------------------------------+
URL: https://mariadb.com/kb/en/pi/https://mariadb.com/kb/en/pi/ D f POWSyntax
------
POW(X,Y)
Description
-----------
Returns the value of X raised to the power of Y.
POWER() is a synonym.
Examples
--------
SELECT POW(2,3);
+----------+
| POW(2,3) |
+----------+
| 8 |
+----------+
SELECT POW(2,-2);
+-----------+
| POW(2,-2) |
+-----------+
| 0.25 |
+-----------+
URL: https://mariadb.com/kb/en/pow/https://mariadb.com/kb/en/pow/ E � POWERSyntax
------
POWER(X,Y)
Description
-----------
This is a synonym for POW(), which returns the value of X
raised to the power of Y.
URL: https://mariadb.com/kb/en/power/https://mariadb.com/kb/en/power/ F " RADIANSSyntax
------
RADIANS(X)
Description
-----------
Returns the argument X, converted from degrees to radians.
Note that
π radians equals 180 degrees.
This is the converse of the DEGREES() function.
Examples
--------
SELECT RADIANS(45);
+-------------------+
| RADIANS(45) |
+-------------------+
| 0.785398163397448 |
+-------------------+
SELECT RADIANS(90);
+-----------------+
| RADIANS(90) |
+-----------------+
| 1.5707963267949 |
+-----------------+
SELECT RADIANS(PI());
+--------------------+
| RADIANS(PI()) |
+--------------------+
| 0.0548311355616075 |
+--------------------+
SELECT RADIANS(180);
+------------------+
| RADIANS(180) |
+------------------+
| 3.14159265358979 |
+------------------+
URL: https://mariadb.com/kb/en/radians/https://mariadb.com/kb/en/radians/ G � RANDSyntax
------
RAND(), RAND(N)
Description
-----------
Returns a random DOUBLE precision floating point value v in
the range 0
URL: https://mariadb.com/kb/en/rand/https://mariadb.com/kb/en/rand/ H � ROUNDSyntax
------
ROUND(X), ROUND(X,D)
Description
-----------
Rounds the argument X to D decimal places. The rounding
algorithm
depends on the data type of X. D defaults to 0 if not
specified.
D can be negative to cause D digits left of the decimal
point of the
value X to become zero.
Examples
--------
SELECT ROUND(-1.23);
+--------------+
| ROUND(-1.23) |
+--------------+
| -1 |
+--------------+
SELECT ROUND(-1.58);
+--------------+
| ROUND(-1.58) |
+--------------+
| -2 |
+--------------+
SELECT ROUND(1.58);
+-------------+
| ROUND(1.58) |
+-------------+
| 2 |
+-------------+
SELECT ROUND(1.298, 1);
+-----------------+
| ROUND(1.298, 1) |
+-----------------+
| 1.3 |
+-----------------+
SELECT ROUND(1.298, 0);
+-----------------+
| ROUND(1.298, 0) |
+-----------------+
| 1 |
+-----------------+
SELECT ROUND(23.298, -1);
+-------------------+
| ROUND(23.298, -1) |
+-------------------+
| 20 |
+-------------------+
URL: https://mariadb.com/kb/en/round/https://mariadb.com/kb/en/round/ I � SIGNSyntax
------
SIGN(X)
Description
-----------
Returns the sign of the argument as -1, 0, or 1, depending
on whether
X is negative, zero, or positive.
Examples
--------
SELECT SIGN(-32);
+-----------+
| SIGN(-32) |
+-----------+
| -1 |
+-----------+
SELECT SIGN(0);
+---------+
| SIGN(0) |
+---------+
| 0 |
+---------+
SELECT SIGN(234);
+-----------+
| SIGN(234) |
+-----------+
| 1 |
+-----------+
URL: https://mariadb.com/kb/en/sign/https://mariadb.com/kb/en/sign/ J @ SINSyntax
------
SIN(X)
Description
-----------
Returns the sine of X, where X is given in radians.
Examples
--------
SELECT SIN(1.5707963267948966);
+-------------------------+
| SIN(1.5707963267948966) |
+-------------------------+
| 1 |
+-------------------------+
SELECT SIN(PI());
+----------------------+
| SIN(PI()) |
+----------------------+
| 1.22460635382238e-16 |
+----------------------+
SELECT ROUND(SIN(PI()));
+------------------+
| ROUND(SIN(PI())) |
+------------------+
| 0 |
+------------------+
URL: https://mariadb.com/kb/en/sin/https://mariadb.com/kb/en/sin/ K & SQRTSyntax
------
SQRT(X)
Description
-----------
Returns the square root of X. If X is negative, NULL is
returned.
Examples
--------
SELECT SQRT(4);
+---------+
| SQRT(4) |
+---------+
| 2 |
+---------+
SELECT SQRT(20);
+------------------+
| SQRT(20) |
+------------------+
| 4.47213595499958 |
+------------------+
SELECT SQRT(-16);
+-----------+
| SQRT(-16) |
+-----------+
| NULL |
+-----------+
SELECT SQRT(1764);
+------------+
| SQRT(1764) |
+------------+
| 42 |
+------------+
URL: https://mariadb.com/kb/en/sqrt/https://mariadb.com/kb/en/sqrt/ L � TANSyntax
------
TAN(X)
Description
-----------
Returns the tangent of X, where X is given in radians.
Examples
--------
SELECT TAN(0.7853981633974483);
+-------------------------+
| TAN(0.7853981633974483) |
+-------------------------+
| 0.9999999999999999 |
+-------------------------+
SELECT TAN(PI());
+-----------------------+
| TAN(PI()) |
+-----------------------+
| -1.22460635382238e-16 |
+-----------------------+
SELECT TAN(PI()+1);
+-----------------+
| TAN(PI()+1) |
+-----------------+
| 1.5574077246549 |
+-----------------+
SELECT TAN(RADIANS(PI()));
+--------------------+
| TAN(RADIANS(PI())) |
+--------------------+
| 0.0548861508080033 |
+--------------------+
URL: https://mariadb.com/kb/en/tan/https://mariadb.com/kb/en/tan/� @ � �N o6* Plugin Overview S )) MBR DefinitionDescription
-----------
The MBR (Minimum Bounding Rectangle), or Envelope is the
bounding
geometry, formed by the minimum and maximum (X,Y)
coordinates:
Examples
--------
((MINX MINY, MAXX MINY, MAXX MAXY, MINX MAXY, MINX MINY))
URL: https://mariadb.com/kb/en/mbr-definition/https://mariadb.com/kb/en/mbr-definition/ T �& MBRContainsSyntax
------
MBRContains(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether the Minimum Bounding
Rectangle of
g1 contains the Minimum Bounding Rectangle of g2. This tests
the
opposite relationship as MBRWithin().
Examples
--------
SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Point(1 1)');
SELECT MBRContains(@g1,@g2), MBRContains(@g2,@g1);
+----------------------+----------------------+
| MBRContains(@g1,@g2) | MBRContains(@g2,@g1) |
+----------------------+----------------------+
| 1 | 0 |
+----------------------+----------------------+
URL: https://mariadb.com/kb/en/mbrcontains/https://mariadb.com/kb/en/mbrcontains/ ���nU3 =�Wwo��j � � LEY� ��tP hG
�< �x M �# TRUNCATEThis page documents the TRUNCATE function. See TRUNCATE
TABLE for the DDL statement.
Syntax
------
TRUNCATE(X,D)
Description
-----------
Returns the number X, truncated to D decimal places. If D is
0, the
result has no decimal point or fractional part. D can be
negative to
cause D digits left of the decimal point of the value X to
become
zero.
Examples
--------
SELECT TRUNCATE(1.223,1);
+-------------------+
| TRUNCATE(1.223,1) |
+-------------------+
| 1.2 |
+-------------------+
SELECT TRUNCATE(1.999,1);
+-------------------+
| TRUNCATE(1.999,1) |
+-------------------+
| 1.9 |
+-------------------+
SELECT TRUNCATE(1.999,0);
+-------------------+
| TRUNCATE(1.999,0) |
+-------------------+
| 1 |
+-------------------+
SELECT TRUNCATE(-1.999,1);
+--------------------+
| TRUNCATE(-1.999,1) |
+--------------------+
| -1.9 |
+--------------------+
SELECT TRUNCATE(122,-2);
+------------------+
| TRUNCATE(122,-2) |
+------------------+
| 100 |
+------------------+
SELECT TRUNCATE(10.28*100,0);
+-----------------------+
| TRUNCATE(10.28*100,0) |
+-----------------------+
| 1028 |
+-----------------------+
URL: https://mariadb.com/kb/en/truncate/https://mariadb.com/kb/en/truncate/ O E) INSTALL PLUGINSyntax
------
INSTALL PLUGIN [IF NOT EXISTS] plugin_name SONAME
'plugin_library'
Description
-----------
This statement installs an individual plugin from the
specified library. To install the whole library (which could
be required), use INSTALL SONAME.
plugin_name is the name of the plugin as defined in the
plugin declaration structure contained in the library file.
Plugin names are
not case sensitive. For maximal compatibility, plugin names
should be limited
to ASCII letters, digits, and underscore, because they are
used in C source
files, shell command lines, M4 and Bourne shell scripts, and
SQL environments.
plugin_library is the name of the shared library that
contains the plugin code. Before MariaDB 5.5.21, the name
should include the file name extension (for
example, libmyplugin.so or libmyplugin.dll). Starting from
MariaDB 5.5.21, the file name extension can be omitted
(which makes the statement look the same on all
architectures).
The shared library must be located in the plugin directory
(that is,
the directory named by the plugin_dir system variable). The
library must be in the plugin directory itself, not in a
subdirectory. By
default, plugin_dir is plugin directory under the directory
named by
the pkglibdir configuration variable, but it can be changed
by setting
the value of plugin_dir at server startup. For example, set
its value in a my.cnf file:
[mysqld]
plugin_dir=/path/to/plugin/directory
If the value of plugin_dir is a relative path name, it is
taken to be relative to the MySQL base directory (the value
of the basedir
system variable).
INSTALL PLUGIN adds a line to the mysql.plugin table that
describes the plugin. This table contains the plugin name
and library file
name.
INSTALL PLUGIN causes the server to read
option (my.cnf) files just as during server startup. This
enables the plugin to
pick up any relevant options from those files. It is
possible to add plugin
options to an option file even before loading a plugin (if
the loose prefix is
used). It is also possible to uninstall a plugin, edit
my.cnf, and install the
plugin again. Restarting the plugin this way enables it to
the new option
values without a server restart.
Before MySQL 5.1.33, a plugin was started with each option
set to its
default value.
INSTALL PLUGIN also loads and initializes the plugin code to
make the plugin available for use. A plugin is initialized
by executing its
initialization function, which handles any setup that the
plugin must perform
before it can be used.
To use INSTALL PLUGIN, you must have the
INSERT privilege for the mysql.plugin table.
At server startup, the server loads and initializes any
plugin that is
listed in the mysql.plugin table. This means that a plugin
is installed
with INSTALL PLUGIN only once, not every time the server
starts. Plugin loading at startup does not occur if the
server is started with
the --skip-grant-tables option.
When the server shuts down, it executes the deinitialization
function
for each plugin that is loaded so that the plugin has a
chance to
perform any final cleanup.
If you need to load plugins for a single server startup when
the
--skip-grant-tables option is given (which tells the server
not to read system tables), use the
--plugin-load mysqld option.
IF NOT EXISTS
When the IF NOT EXISTS clause is used, MariaDB will return a
note instead of an error if the specified plugin already
exists. See SHOW WARNINGS.
Examples
--------
INSTALL PLUGIN sphinx SONAME 'ha_sphinx.so';
Starting from MariaDB 5.5.21, the extension can be omitted:
INSTALL PLUGIN innodb SONAME 'ha_xtradb';
From MariaDB 10.4.0:
INSTALL PLUGIN IF NOT EXISTS example SONAME 'ha_example';
Query OK, 0 rows affected (0.104 sec)
INSTALL PLUGIN IF NOT EXISTS example SONAME 'ha_example';
Query OK, 0 rows affected, 1 warning (0.000 sec)
SHOW WARNINGS;
+-------+------+------------------------------------+
| Level | Code | Message |
+-------+------+------------------------------------+
| Note | 1968 | Plugin 'example' already installed |
+-------+------+------------------------------------+
URL: https://mariadb.com/kb/en/install-plugin/https://mariadb.com/kb/en/install-plugin/ V �# MBREqualSyntax
------
MBREqual(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether the Minimum Bounding
Rectangles of
the two geometries g1 and g2 are the same.
Examples
--------
SET @g1=GEOMFROMTEXT('LINESTRING(0 0, 1 2)');
SET @g2=GEOMFROMTEXT('POLYGON((0 0, 0 2, 1 2, 1 0, 0
0))');
SELECT MbrEqual(@g1,@g2);
+-------------------+
| MbrEqual(@g1,@g2) |
+-------------------+
| 1 |
+-------------------+
SET @g1=GEOMFROMTEXT('LINESTRING(0 0, 1 3)');
SET @g2=GEOMFROMTEXT('POLYGON((0 0, 0 2, 1 4, 1 0, 0
0))');
SELECT MbrEqual(@g1,@g2);
+-------------------+
| MbrEqual(@g1,@g2) |
+-------------------+
| 0 |
+-------------------+
URL: https://mariadb.com/kb/en/mbrequal/https://mariadb.com/kb/en/mbrequal/ Z �$ MBRWithinSyntax
------
MBRWithin(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether the Minimum Bounding
Rectangle of
g1 is within the Minimum Bounding Rectangle of g2. This
tests the
opposite relationship as MBRContains().
Examples
--------
SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((0 0,0 5,5 5,5 0,0 0))');
SELECT MBRWithin(@g1,@g2), MBRWithin(@g2,@g1);
+--------------------+--------------------+
| MBRWithin(@g1,@g2) | MBRWithin(@g2,@g1) |
+--------------------+--------------------+
| 1 | 0 |
+--------------------+--------------------+
URL: https://mariadb.com/kb/en/mbrwithin/https://mariadb.com/kb/en/mbrwithin/ \ �& IF FunctionSyntax
------
IF(expr1,expr2,expr3)
Description
-----------
If expr1 is TRUE (expr1 0 and expr1 NULL) then IF()
returns expr2; otherwise it returns expr3. IF() returns a
numeric
or string value, depending on the context in which it is
used.
Note: There is also an IF statement which differs from the
IF() function described here.
Examples
--------
SELECT IF(1>2,2,3);
+-------------+
| IF(1>2,2,3) |
+-------------+
| 3 |
+-------------+
SELECT IF(1
URL: https://mariadb.com/kb/en/if-function/https://mariadb.com/kb/en/if-function/ 6:d�k��� ��'� Plugins are server components that enhance MariaDB in some
way. These can be anything from new storage engines, plugins
for enhancing full-text parsing, or even small enhancements,
such as a plugin to get a timestamp as an integer.
Querying Plugin Information
There are a number of ways to see which plugins are
currently active.
A server almost always has a large number of active plugins,
because the server contains a large number of built-in
plugins, which are active by default and cannot be
uninstalled.
Querying Plugin Information with SHOW PLUGINS
The SHOW PLUGINS statement can be used to query information
about all active plugins.
For example:
SHOW PLUGINS;
+----------------------------+----------+--------------------+---------+---------+
| Name | Status | Type | Library | License |
+----------------------------+----------+--------------------+---------+---------+
...
| mysql_native_password | ACTIVE | AUTHENTICATION | NULL |
GPL |
| mysql_old_password | ACTIVE | AUTHENTICATION | NULL | GPL
|
| MRG_MyISAM | ACTIVE | STORAGE ENGINE | NULL | GPL |
...
+----------------------------+----------+--------------------+---------+---------+
If a plugin's Library column has the NULL value, then the
plugin is built-in, and it cannot be uninstalled.
Querying Plugin Information with information_schema.PLUGINS
The information_schema.PLUGINS table can be queried to get
more detailed information about plugins.
For example:
SELECT * FROM information_schema.PLUGINS\G
...
*************************** 6. row
***************************
PLUGIN_NAME: CSV
PLUGIN_VERSION: 1.0
PLUGIN_STATUS: ACTIVE
PLUGIN_TYPE: STORAGE ENGINE
PLUGIN_TYPE_VERSION: 100003.0
PLUGIN_LIBRARY: NULL
PLUGIN_LIBRARY_VERSION: NULL
PLUGIN_AUTHOR: Brian Aker, MySQL AB
PLUGIN_DESCRIPTION: CSV storage engine
PLUGIN_LICENSE: GPL
LOAD_OPTION: FORCE
PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
*************************** 7. row
***************************
PLUGIN_NAME: MEMORY
PLUGIN_VERSION: 1.0
PLUGIN_STATUS: ACTIVE
PLUGIN_TYPE: STORAGE ENGINE
PLUGIN_TYPE_VERSION: 100003.0
PLUGIN_LIBRARY: NULL
PLUGIN_LIBRARY_VERSION: NULL
PLUGIN_AUTHOR: MySQL AB
PLUGIN_DESCRIPTION: Hash based, stored in memory, useful
for temporary tables
PLUGIN_LICENSE: GPL
LOAD_OPTION: FORCE
PLUGIN_MATURITY: Stable
PLUGIN_AUTH_VERSION: 1.0
...
If a plugin's PLUGIN_LIBRARY column has the NULL value,
then the plugin is built-in, and it cannot be uninstalled.
Querying Plugin Information with mysql.plugin
The mysql.plugin table can be queried to get information
about installed plugins.
This table only contains information about plugins that have
been installed via the following methods:
The INSTALL SONAME statement.
The INSTALL PLUGIN statement.
The mysql_plugin utility.
This table does not contain information about:
Built-in plugins.
Plugins loaded with the --plugin-load-add option.
Plugins loaded with the --plugin-load option.
This table only contains enough information to reload the
plugin when the server is restarted, which means it only
contains the plugin name and the plugin library.
For example:
SELECT * FROM mysql.plugin;
+------+------------+
| name | dl |
+------+------------+
| PBXT | libpbxt.so |
+------+------------+
Installing a Plugin
There are three primary ways to install a plugin:
A plugin can be installed dynamically with an SQL statement.
A plugin can be installed with a mysqld option, but it
requires a server restart.
A plugin can be installed with the mysql_plugin utility,
while the server is completely offline.
When you are installing a plugin, you also have to ensure
that:
The server's plugin directory is properly configured, and
the plugin's library is in the plugin directory.
The server's minimum plugin maturity is properly
configured, and the plugin is mature enough to be installed.
Installing a Plugin Dynamically
A plugin can be installed dynamically by executing either
the INSTALL SONAME or the INSTALL PLUGIN statement.
If a plugin is installed with one of these statements, then
a record will be added to the mysql.plugins table for the
plugin. This means that the plugin will automatically be
loaded every time the server restarts, unless specifically
uninstalled or deactivated.
Installing a Plugin with INSTALL SONAME
You can install a plugin dynamically by executing the
INSTALL SONAME statement. INSTALL SONAME installs all
plugins from the given plugin library. This could be
required for some plugin libraries.
For example, to install all plugins in the server_audit
plugin library (which is currently only the server_audit
audit plugin), you could execute the following:
INSTALL SONAME 'server_audit';
Installing a Plugin with INSTALL PLUGIN
You can install a plugin dynamically by executing the
INSTALL PLUGIN statement. INSTALL PLUGIN installs a single
plugin from the given plugin library.
For example, to install the server_audit audit plugin from
the server_audit plugin library, you could execute the
following:
INSTALL PLUGIN server_audit SONAME 'server_audit';
Installing a Plugin with Plugin Load Options
A plugin can be installed with a mysqld option by providing
either the --plugin-load-add or the --plugin-load option.
If a plugin is installed with one of these options, then a
record will not be added to the mysql.plugins table for the
plugin. This means that if the server is restarted without
the same option set, then the plugin will not automatically
be loaded.
Installing a Plugin with --plugin-load-add
You can install a plugin with the --plugin-load-add option
by specifying the option as a command-line argument to
mysqld or by specifying the option in a relevant server
option group in an option file.
The --plugin-load-add option uses the following format:
Plugins can be specified in the format name=library, where
name is the plugin name and library is the plugin library.
This format installs a single plugin from the given plugin
library.
Plugins can also be specified in the format library, where
library is the plugin library. This format installs all
plugins from the given plugin library.
Multiple plugins can be specified by separating them with
semicolons.
For example, to install all plugins in the server_audit
plugin library (which is currently only the server_audit
audit plugin) and also the ed25519 authentication plugin
from the auth_ed25519 plugin library, you could set the
option to the following values on the command-line:
$ mysqld --user=mysql --plugin-load-add='server_audit'
--plugin-load-add='ed25519=auth_ed25519'
You could also set the option to the same values in an
option file:
[mariadb]
...
plugin_load_add = server_audit
plugin_load_add = ed25519=auth_ed25519
Special care must be taken when specifying both the
--plugin-load option and the --plugin-load-add option
together. The --plugin-load option resets the plugin load
list, and this can cause unexpected problems if you are not
aware. The --plugin-load-add option does not reset the
plugin load list, so it is much safer to use. See Specifying
Multiple Plugin Load Options for more information.
Installing a Plugin with --plugin-load
You can install a plugin with the --plugin-load option by
specifying the option as a command-line argument to mysqld
or by specifying the option in a relevant server option
group in an option file.
The --plugin-load option uses the following format:
Plugins can be specified in the format name=library, where
name is the plugin name and library is the plugin library.
This format installs a single plugin from the given plugin
library.
Plugins can also be specified in the format library, where
library is the plugin library. This format installs all
plugins from the given plugin library.
Multiple plugins can be specified by separating them with
semicolons.
For example, to install all plugins in the server_audit
plugin library (which is currently only the server_audit
audit plugin) and also the ed25519 authentication plugin
from the auth_ed25519 plugin library, you could set the
option to the following values on the command-line:
$ mysqld --user=mysql
--plugin-load='server_���� ��Vaudit;ed25519=auth_ed25519'
You could also set the option to the same values in an
option file:
[mariadb]
...
plugin_load = server_audit;ed25519=auth_ed25519
Special care must be taken when specifying the --plugin-load
option multiple times, or when specifying both the
--plugin-load option and the --plugin-load-add option
together. The --plugin-load option resets the plugin load
list, and this can cause unexpected problems if you are not
aware. The --plugin-load-add option does not reset the
plugin load list, so it is much safer to use. See Specifying
Multiple Plugin Load Options for more information.
Specifying Multiple Plugin Load Options
Special care must be taken when specifying the --plugin-load
option multiple times, or when specifying both the
--plugin-load option and the --plugin-load-add option. The
--plugin-load option resets the plugin load list, and this
can cause unexpected problems if you are not aware. The
--plugin-load-add option does not reset the plugin load
list, so it is much safer to use.
This can have the following consequences:
If the --plugin-load option is specified multiple times,
then only the last instance will have any effect. For
example, in the following case, the first instance of the
option is reset:
[mariadb]
...
plugin_load = server_audit
plugin_load = ed25519=auth_ed25519
If the --plugin-load option is specified after the
--plugin-load-add option, then it will also reset the
changes made by that option. For example, in the following
case, the --plugin-load-add option does not do anything,
because the subsequent --plugin-load option resets the
plugin load list:
[mariadb]
...
plugin_load_add = server_audit
plugin_load = ed25519=auth_ed25519
In contrast, if the --plugin-load option is specified before
the --plugin-load-add option, then it will work fine,
because the --plugin-load-add option does not reset the
plugin load list. For example, in the following case, both
plugins are properly loaded:
[mariadb]
...
plugin_load = server_audit
plugin_load_add = ed25519=auth_ed25519
Installing a Plugin with mysql_plugin
A plugin can be installed with the mysql_plugin utility if
the server is completely offline.
The syntax is:
mysql_plugin [options]
ENABLE|DISABLE
For example, to install the server_audit audit plugin, you
could execute the following:
mysql_plugin server_audit ENABLE
If a plugin is installed with this utility, then a record
will be added to the mysql.plugins table for the plugin.
This means that the plugin will automatically be loaded
every time the server restarts, unless specifically
uninstalled or deactivated.
Configuring the Plugin Directory
When a plugin is being installed, the server looks for the
plugin's library in the server's plugin directory. This
directory is configured by the plugin_dir system variable.
This can be specified as a command-line argument to mysqld
or it can be specified in a relevant server option group in
an option file. For example:
[mariadb]
...
plugin_dir = /usr/lib64/mysql/plugin
Configuring the Minimum Plugin Maturity
When a plugin is being installed, the server compares the
plugin's maturity level against the server's minimum
allowed plugin maturity. This can help prevent users from
using unstable plugins on production servers. This minimum
plugin maturity is configured by the plugin_maturity system
variable. This can be specified as a command-line argument
to mysqld or it can be specified in a relevant server option
group in an option file. For example:
[mariadb]
...
plugin_maturity = stable
Configuring Plugin Activation at Server Startup
A plugin will be loaded by default when the server starts
if:
The plugin was installed with the INSTALL SONAME statement.
The plugin was installed with the INSTALL PLUGIN statement.
The plugin was installed with the mysql_plugin utility.
The server is configured to load the plugin with the
--plugin-load-add option.
The server is configured to load the plugin with the
--plugin-load option.
This behavior can be changed with special options that take
the form --plugin-name. For example, for the server_audit
audit plugin, the special option is called --server-audit.
The possible values for these special options are:
Option Value | Description |
OFF | Disables the plugin without removing it from the
mysql.plugins table. |
ON | Enables the plugin. If the plugin cannot be
initialized, then the server will still continue starting
up, but the plugin will be disabled. |
FORCE | Enables the plugin. If the plugin cannot be
initialized, then the server will fail to start with an
error. |
FORCE_PLUS_PERMANENT | Enables the plugin. If the plugin
cannot be initialized, then the server will fail to start
with an error. In addition, the plugin cannot be uninstalled
with UNINSTALL SONAME or UNINSTALL PLUGIN while the server
is running. |
A plugin's status can be found by looking at the
PLUGIN_STATUS column of the information_schema.PLUGINS
table.
Uninstalling Plugins
Plugins that are found in the mysql.plugin table, that is
those that were installed with INSTALL SONAME, INSTALL
PLUGIN or mysql_plugin can be uninstalled in one of two
ways:
The UNINSTALL SONAME or the UNINSTALL PLUGIN statement while
the server is running
With mysql_plugin while the server is offline.
Plugins that were enabled as a --plugin-load option do not
need to be uninstalled. If --plugin-load is omitted the next
time the server starts, or the plugin is not listed as one
of the --plugin-load entries, the plugin will not be loaded.
UNINSTALL PLUGIN uninstalls a single installed plugin, while
UNINSTALL SONAME uninstalls all plugins belonging to a given
library.
URL: https://mariadb.com/kb/en/plugin-overview/https://mariadb.com/kb/en/change-master-to/ltiple XA-capable storage engines by default, even if the
only "real" storage engine that supports external XA
transactions enabled on these builds by default is InnoDB.
Therefore, when using one these builds MariaDB would be
forced to use a transaction coordinator log by default,
which could have performance implications.
See Transaction Coordinator Log Overview: MariaDB Galera
Cluster for more information.
URL: https://mariadb.com/kb/en/xa-transactions/n method for the user
account by executing the following:
ALTER USER root@localhost IDENTIFIED VIA
mysql_native_password USING PASSWORD("verysecret")
URL:
https://mariadb.com/kb/en/authentication-from-mariadb-104/https://mariadb.com/kb/en/create-user/ l& �� ���+ { � � �� https://mariadb.com/kb/en/plugin-overview/position updated as it applies
events.
The relay_log_info_file system variable can be set either on
the command-line or in a server option group in an option
file prior to starting up the server. For example:
[mariadb]
...
relay_log_info_file=/mariadb/myserver1-relay-log.info
GTID Persistence
If the slave is replicating binary log events that contain
GTIDs, then the slave's SQL thread will write every GTID
that it applies to the mysql.gtid_slave_pos table. This GTID
can be inspected and modified through the gtid_slave_pos
system variable.
If the slave has the log_slave_updates system variable
enabled and if the slave has the binary log enabled, then
every write by the slave's SQL thread will also go into the
slave's binary log. This means that GTIDs of replicated
transactions would be reflected in the value of the
gtid_binlog_pos system variable.
Creating a Slave from a Backup
The CHANGE MASTER statement is useful for setting up a slave
when you have a backup of the master and you also have the
binary log position or GTID position corresponding to the
backup.
After restoring the backup on the slave, you could execute
something like this to use the binary log position:
CHANGE MASTER TO
MASTER_LOG_FILE='master2-bin.001',
MASTER_LOG_POS=4;
START SLAVE;
Or you could execute something like this to use the GTID
position:
SET GLOBAL gtid_slave_pos='0-1-153';
CHANGE MASTER TO
MASTER_USE_GTID=slave_pos;
START SLAVE;
See Setting up a Replication Slave with Mariabackup for more
information on how to do this with Mariabackup.
Example
The following example changes the master and master's
binary log coordinates.
This is used when you want to set up the slave to replicate
the master:
CHANGE MASTER TO
MASTER_HOST='master2.mycompany.com',
MASTER_USER='replication',
MASTER_PASSWORD='bigs3cret',
MASTER_PORT=3306,
MASTER_LOG_FILE='master2-bin.001',
MASTER_LOG_POS=4,
MASTER_CONNECT_RETRY=10;
START SLAVE;
URL: https://mariadb.com/kb/en/change-master-to/https://mariadb.com/kb/en/xa-transactions/https://mariadb.com/kb/en/authentication-from-mariadb-104/;
ALTER TABLE mysql.procs_priv MODIFY Grantor CHAR(141)
COLLATE utf8_bin NOT NULL DEFAULT '';
ALTER TABLE mysql.tables_priv MODIFY Grantor CHAR(141)
COLLATE utf8_bin NOT NULL DEFAULT '';
FLUSH PRIVILEGES;
Anonymous Accounts
Anonymous accounts are accounts where the user name portion
of the account name is empty. These accounts act as special
catch-all accounts. If a user attempts to log into the
system from a host, and an anonymous account exists with a
host name portion that matches the user's host, then the
user will log in as the anonymous account if there is no
more specific account match for the user name that the user
entered.
For example, here are some anonymous accounts:
CREATE USER ''@'localhost';
CREATE USER ''@'192.168.0.3';
Fixing a Legacy Default Anonymous Account
On some systems, the mysql.db table has some entries for the
''@'%' anonymous account by default. Unfortunately,
there is no matching entry in the mysql.user table, which
means that this anonymous account doesn't exactly exist,
but it does have privileges--usually on the default test
database created by mysql_install_db. These account-less
privileges are a legacy that is leftover from a time when
MySQL's privilege system was less advanced.
This situation means that you will run into errors if you
try to create a ''@'%' account. For example:
CREATE USER ''@'%';
ERROR 1396 (HY000): Operation CREATE USER failed for
''@'%'
The fix is to DELETE the row in the mysql.db table and then
execute FLUSH PRIVILEGES:
DELETE FROM mysql.db WHERE User='' AND Host='%';
FLUSH PRIVILEGES;
And then the account can be created:
CREATE USER ''@'%';
Query OK, 0 rows affected (0.01 sec)
See MDEV-13486 for more information.
Password Expiry
Besides automatic password expiry, as determined by
default_password_lifetime, password expiry times can be set
on an individual user basis, overriding the global setting,
for example:
CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL
120 DAY;
See User Password Expiry for more details.
Account Locking
Account locking permits privileged administrators to
lock/unlock user accounts. No new client connections will be
permitted if an account is locked (existing connections are
not affected). For example:
CREATE USER 'marijn'@'localhost' ACCOUNT LOCK;
See Account Locking for more details.
URL: https://mariadb.com/kb/en/create-user/https://mariadb.com/kb/en/alter-user/https://mariadb.com/kb/en/grant/
To flush some of the global caches that take up memory, you
could execute the following command:
FLUSH LOCAL HOSTS,
QUERY CACHE,
TABLE_STATISTICS,
INDEX_STATISTICS,
USER_STATISTICS;
URL: https://mariadb.com/kb/en/flush/https://mariadb.com/kb/en/show-slave-status/ssions_reused | 0 |
| Ssl_used_session_cache_entries | 0 |
| Ssl_verify_depth | 0 |
| Ssl_verify_mode | 0 |
| Ssl_version | |
| Subquery_cache_hit | 0 |
| Subquery_cache_miss | 0 |
| Syncs | 2 |
| Table_locks_immediate | 21 |
| Table_locks_waited | 0 |
| Tc_log_max_pages_used | 0 |
| Tc_log_page_size | 4096 |
| Tc_log_page_waits | 0 |
| Threadpool_idle_threads | 0 |
| Threadpool_threads | 0 |
| Threads_cached | 0 |
| Threads_connected | 1 |
| Threads_created | 2 |
| Threads_running | 1 |
| Update_scan | 0 |
| Uptime | 223 |
| Uptime_since_flush_status | 223 |
| wsrep_cluster_conf_id | 18446744073709551615 |
| wsrep_cluster_size | 0 |
| wsrep_cluster_state_uuid | |
| wsrep_cluster_status | Disconnected |
| wsrep_connected | OFF |
| wsrep_local_bf_aborts | 0 |
| wsrep_local_index | 18446744073709551615 |
| wsrep_provider_name | |
| wsrep_provider_vendor | |
| wsrep_provider_version | |
| wsrep_ready | OFF |
| wsrep_thread_count | 0 |
+--------------------------------------------------------------+----------------------------------------+
516 rows in set (0.00 sec)
Example of filtered output:
SHOW STATUS LIKE 'Key%';
+------------------------+--------+
| Variable_name | Value |
+------------------------+--------+
| Key_blocks_not_flushed | 0 |
| Key_blocks_unused | 107163 |
| Key_blocks_used | 0 |
| Key_blocks_warm | 0 |
| Key_read_requests | 0 |
| Key_reads | 0 |
| Key_write_requests | 0 |
| Key_writes | 0 |
+------------------------+--------+
8 rows in set (0.00 sec)
URL: https://mariadb.com/kb/en/show-status/-------------------+------+---------------+------+---------+------+------+-------------+
| 1 | SIMPLE | employees_example | ALL | NULL | NULL | NULL
| NULL | 6 | Using where |
+------+-------------+-------------------+------+---------------+------+---------+------+------+-------------+
Here, the type is All, which means no index could be used.
Looking at the rows count, a full table scan (all six rows)
had to be performed in order to retrieve the record. If
it's a requirement to search by phone number, an index will
have to be created.
SHOW EXPLAIN example:
SHOW EXPLAIN FOR 1;
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
| id | select_type | table | type | possible_keys | key |
key_len | ref | rows | Extra |
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
| 1 | SIMPLE | tbl | index | NULL | a | 5 | NULL | 1000107 |
Using index |
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
1 row in set, 1 warning (0.00 sec)
Example of ref_or_null optimization
SELECT * FROM table_name
WHERE key_column=expr OR key_column IS NULL;
ref_or_null is something that often happens when you use
subqueries with NOT IN as then one has to do an extra check
for NULL values if the first value didn't have a matching
row.
URL: https://mariadb.com/kb/en/explain/ l�V*, /� �% {o A: * 6 � * �Iyi �� P s+ UNINSTALL PLUGINSyntax
------
UNINSTALL PLUGIN [IF EXISTS] plugin_name
Description
-----------
This statement removes a single installed plugin. To
uninstall the whole library which contains the plugin, use
UNINSTALL SONAME. You cannot uninstall a plugin if any table
that uses it is open.
plugin_name must be the name of some plugin that is listed
in the mysql.plugin table. The server executes the plugin's
deinitialization
function and removes the row for the plugin from the
mysql.plugin
table, so that subsequent server restarts will not load and
initialize
the plugin. UNINSTALL PLUGIN does not remove the plugin's
shared library file.
To use UNINSTALL PLUGIN, you must have the
DELETE privilege for the mysql.plugin table.
IF EXISTS
If the IF EXISTS clause is used, MariaDB will return a note
instead of an error if the plugin does not exist. See SHOW
WARNINGS.
Examples
--------
UNINSTALL PLUGIN example;
From MariaDB 10.4.0:
UNINSTALL PLUGIN IF EXISTS example;
Query OK, 0 rows affected (0.099 sec)
UNINSTALL PLUGIN IF EXISTS example;
Query OK, 0 rows affected, 1 warning (0.000 sec)
SHOW WARNINGS;
+-------+------+-------------------------------+
| Level | Code | Message |
+-------+------+-------------------------------+
| Note | 1305 | PLUGIN example does not exist |
+-------+------+-------------------------------+
URL: https://mariadb.com/kb/en/uninstall-plugin/https://mariadb.com/kb/en/uninstall-plugin/ Q c ) INSTALL SONAMEINSTALL SONAME has been supported since MariaDB 5.5.21.
Syntax
------
INSTALL SONAME 'plugin_library'
Description
-----------
This statement is a variant of INSTALL PLUGIN. It installs
all plugins from a given plugin_library. See INSTALL PLUGIN
for details.
plugin_library is the name of the shared library that
contains the plugin code. The file name extension (for
example, libmyplugin.so or libmyplugin.dll) can be omitted
(which makes the statement look the same on all
architectures).
The shared library must be located in the plugin directory
(that is,
the directory named by the plugin_dir system variable). The
library must be in the plugin directory itself, not in a
subdirectory. By
default, plugin_dir is plugin directory under the directory
named by
the pkglibdir configuration variable, but it can be changed
by setting
the value of plugin_dir at server startup. For example, set
its value in a my.cnf file:
[mysqld]
plugin_dir=/path/to/plugin/directory
If the value of plugin_dir is a relative path name, it is
taken to be relative to the MySQL base directory (the value
of the basedir
system variable).
INSTALL SONAME adds one or more lines to the mysql.plugin
table that
describes the plugin. This table contains the plugin name
and library file
name.
INSTALL SONAME causes the server to read
option (my.cnf) files just as during server startup. This
enables the plugin to
pick up any relevant options from those files. It is
possible to add plugin
options to an option file even before loading a plugin (if
the loose prefix is
used). It is also possible to uninstall a plugin, edit
my.cnf, and install the
plugin again. Restarting the plugin this way enables it to
the new option
values without a server restart.
INSTALL SONAME also loads and initializes the plugin code to
make the plugin available for use. A plugin is initialized
by executing its
initialization function, which handles any setup that the
plugin must perform
before it can be used.
To use INSTALL SONAME, you must have the
INSERT privilege for the mysql.plugin table.
At server startup, the server loads and initializes any
plugin that is
listed in the mysql.plugin table. This means that a plugin
is installed
with INSTALL SONAME only once, not every time the server
starts. Plugin loading at startup does not occur if the
server is started with
the --skip-grant-tables option.
When the server shuts down, it executes the deinitialization
function
for each plugin that is loaded so that the plugin has a
chance to
perform any final cleanup.
If you need to load plugins for a single server startup when
the
--skip-grant-tables option is given (which tells the server
not to read system tables), use the
--plugin-load mysqld option.
If you need to install only one plugin from a library, use
the INSTALL PLUGIN statement.
Examples
--------
To load the XtraDB storage engine and all of its
information_schema tables with one statement, use
INSTALL SONAME 'ha_xtradb';
This statement can be used instead of INSTALL PLUGIN even
when the library contains only one plugin:
INSTALL SONAME 'ha_sequence';
URL: https://mariadb.com/kb/en/install-soname/https://mariadb.com/kb/en/install-soname/ R �+ UNINSTALL SONAMEUNINSTALL SONAME has been supported since MariaDB 5.5.21.
Syntax
------
UNINSTALL SONAME [IF EXISTS] 'plugin_library'
Description
-----------
This statement is a variant of UNINSTALL PLUGIN statement,
that removes all plugins belonging to a specified
plugin_library. See UNINSTALL PLUGIN for details.
plugin_library is the name of the shared library that
contains the plugin code. The file name extension (for
example, libmyplugin.so or libmyplugin.dll) can be omitted
(which makes the statement look the same on all
architectures).
To use UNINSTALL SONAME, you must have the
DELETE privilege for the mysql.plugin table.
IF EXISTS
If the IF EXISTS clause is used, MariaDB will return a note
instead of an error if the plugin library does not exist.
See SHOW WARNINGS.
Examples
--------
To uninstall the XtraDB plugin and all of its
information_schema tables with one statement, use
UNINSTALL SONAME 'ha_xtradb';
From MariaDB 10.4.0:
UNINSTALL SONAME IF EXISTS 'ha_example';
Query OK, 0 rows affected (0.099 sec)
UNINSTALL SONAME IF EXISTS 'ha_example';
Query OK, 0 rows affected, 1 warning (0.000 sec)
SHOW WARNINGS;
+-------+------+-------------------------------------+
| Level | Code | Message |
+-------+------+-------------------------------------+
| Note | 1305 | SONAME ha_example.so does not exist |
+-------+------+-------------------------------------+
URL: https://mariadb.com/kb/en/uninstall-soname/https://mariadb.com/kb/en/uninstall-soname/ ] �! IFNULLSyntax
------
IFNULL(expr1,expr2)
Description
-----------
If expr1 is not NULL, IFNULL() returns expr1; otherwise it
returns
expr2. IFNULL() returns a numeric or string value, depending
on the
context in which it is used.
Examples
--------
SELECT IFNULL(1,0);
+-------------+
| IFNULL(1,0) |
+-------------+
| 1 |
+-------------+
SELECT IFNULL(NULL,10);
+-----------------+
| IFNULL(NULL,10) |
+-----------------+
| 10 |
+-----------------+
SELECT IFNULL(1/0,10);
+----------------+
| IFNULL(1/0,10) |
+----------------+
| 10.0000 |
+----------------+
SELECT IFNULL(1/0,'yes');
+-------------------+
| IFNULL(1/0,'yes') |
+-------------------+
| yes |
+-------------------+
URL: https://mariadb.com/kb/en/ifnull/https://mariadb.com/kb/en/ifnull/ ^ �! NULLIFSyntax
------
NULLIF(expr1,expr2)
Description
-----------
Returns NULL if expr1 = expr2 is true, otherwise returns
expr1. This is
the same as CASE WHEN expr1 = expr2 THEN NULL ELSE expr1
END.
Examples
--------
SELECT NULLIF(1,1);
+-------------+
| NULLIF(1,1) |
+-------------+
| NULL |
+-------------+
SELECT NULLIF(1,2);
+-------------+
| NULLIF(1,2) |
+-------------+
| 1 |
+-------------+
URL: https://mariadb.com/kb/en/nullif/https://mariadb.com/kb/en/nullif/ p�ap��� �5�V �0 U G& MBRDisjointSyntax
------
MBRDisjoint(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether the Minimum Bounding
Rectangles of the two geometries g1 and g2 are disjoint. Two
geometries are disjoint if they do not intersect, that is
touch or overlap.
Examples
--------
SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((4 4,4 7,7 7,7 4,4 4))');
SELECTmbrdisjoint(@g1,@g2);
+----------------------+
| mbrdisjoint(@g1,@g2) |
+----------------------+
| 1 |
+----------------------+
SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))');
SELECT mbrdisjoint(@g1,@g2);
+----------------------+
| mbrdisjoint(@g1,@g2) |
+----------------------+
| 0 |
+----------------------+
URL: https://mariadb.com/kb/en/mbrdisjoint/https://mariadb.com/kb/en/mbrdisjoint/ W
( MBRIntersectsSyntax
------
MBRIntersects(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether the Minimum Bounding
Rectangles of the two geometries g1 and g2 intersect.
Examples
--------
SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))');
SELECT mbrintersects(@g1,@g2);
+------------------------+
| mbrintersects(@g1,@g2) |
+------------------------+
| 1 |
+------------------------+
SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((4 4,4 7,7 7,7 4,4 4))');
SELECT mbrintersects(@g1,@g2);
+------------------------+
| mbrintersects(@g1,@g2) |
+------------------------+
| 0 |
+------------------------+
URL: https://mariadb.com/kb/en/mbrintersects/https://mariadb.com/kb/en/mbrintersects/ X �& MBROverlapsSyntax
------
MBROverlaps(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether the Minimum Bounding
Rectangles of
the two geometries g1 and g2 overlap. The term spatially
overlaps is
used if two geometries intersect and their intersection
results in a
geometry of the same dimension but not equal to either of
the given
geometries.
Examples
--------
SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((4 4,4 7,7 7,7 4,4 4))');
SELECT mbroverlaps(@g1,@g2);
+----------------------+
| mbroverlaps(@g1,@g2) |
+----------------------+
| 0 |
+----------------------+
SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))');
SELECT mbroverlaps(@g1,@g2);
+----------------------+
| mbroverlaps(@g1,@g2) |
+----------------------+
| 0 |
+----------------------+
SET @g1 = GeomFromText('Polygon((0 0,0 4,4 4,4 0,0 0))');
SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))');
SELECT mbroverlaps(@g1,@g2);
+----------------------+
| mbroverlaps(@g1,@g2) |
+----------------------+
| 1 |
+----------------------+
URL: https://mariadb.com/kb/en/mbroverlaps/https://mariadb.com/kb/en/mbroverlaps/ Y
�% MBRTouchesSyntax
------
MBRTouches(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether the Minimum Bounding
Rectangles of
the two geometries g1 and g2 touch. Two geometries spatially
touch if
the interiors of the geometries do not intersect, but the
boundary of
one of the geometries intersects either the boundary or the
interior
of the other.
Examples
--------
SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((4 4,4 7,7 7,7 4,4 4))');
SELECT mbrtouches(@g1,@g2);
+---------------------+
| mbrtouches(@g1,@g2) |
+---------------------+
| 0 |
+---------------------+
SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))');
SELECT mbrtouches(@g1,@g2);
+---------------------+
| mbrtouches(@g1,@g2) |
+---------------------+
| 1 |
+---------------------+
SET @g1 = GeomFromText('Polygon((0 0,0 4,4 4,4 0,0 0))');
SET @g2 = GeomFromText('Polygon((3 3,3 6,6 6,6 3,3 3))');
SELECT mbrtouches(@g1,@g2);
+---------------------+
| mbrtouches(@g1,@g2) |
+---------------------+
| 0 |
+---------------------+
URL: https://mariadb.com/kb/en/mbrtouches/https://mariadb.com/kb/en/mbrtouches/ [
�( CASE OPERATORSyntax
------
CASE value WHEN [compare_value] THEN result [WHEN
[compare_value] THEN
result ...] [ELSE result] END
CASE WHEN [condition] THEN result [WHEN [condition] THEN
result ...]
[ELSE result] END
Description
-----------
The first version returns the result where
value=compare_value. The
second version returns the result for the first condition
that is
true. If there was no matching result value, the result
after ELSE is
returned, or NULL if there is no ELSE part.
There is also a CASE statement, which differs from the CASE
operator described here.
Examples
--------
SELECT CASE 1 WHEN 1 THEN 'one' WHEN 2 THEN 'two' ELSE
'more' END;
+------------------------------------------------------------+
| CASE 1 WHEN 1 THEN 'one' WHEN 2 THEN 'two' ELSE
'more' END |
+------------------------------------------------------------+
| one |
+------------------------------------------------------------+
SELECT CASE WHEN 1>0 THEN 'true' ELSE 'false' END;
+--------------------------------------------+
| CASE WHEN 1>0 THEN 'true' ELSE 'false' END |
+--------------------------------------------+
| true |
+--------------------------------------------+
SELECT CASE BINARY 'B' WHEN 'a' THEN 1 WHEN 'b' THEN 2
END;
+-----------------------------------------------------+
| CASE BINARY 'B' WHEN 'a' THEN 1 WHEN 'b' THEN 2 END
|
+-----------------------------------------------------+
| NULL |
+-----------------------------------------------------+
URL: https://mariadb.com/kb/en/case-operator/https://mariadb.com/kb/en/case-operator/� @ � �_ �g+ CHANGE MASTER TO j �' RESET MASTERRESET MASTER [TO #]
Deletes all binary log files listed in the index file,
resets the
binary log index file to be empty, and creates a new binary
log file with a suffix of .000001.
If TO # is given, then the first new binary log file will
start from number #.
This statement is for use only when the master is started
for the first time, and should never be used if any slaves
are actively replicating from the binary log.
URL: https://mariadb.com/kb/en/reset-master/https://mariadb.com/kb/en/reset-master/ q
P5 UNLOCK TABLESSyntax
------
UNLOCK TABLES
Description
-----------
UNLOCK TABLES explicitly releases any table locks held by
the
current session. See LOCK TABLES for more information.
In addition to releasing table locks acquired by the LOCK
TABLES statement, the UNLOCK TABLES statement also releases
the global read lock acquired by the FLUSH TABLES WITH READ
LOCK statement. The FLUSH TABLES WITH READ LOCK statement is
very useful for performing backups. See FLUSH for more
information about FLUSH TABLES WITH READ LOCK.
URL: https://mariadb.com/kb/en/transactions-unlock-tables/https://mariadb.com/kb/en/transactions-unlock-tables/� @ � �s �!* XA Transactions� @ � �u � :
Authentication from MariaDB 10.4� @ � �v WI&
CREATE USER� @ � �w
�,%
ALTER USER n . ? / �D �3 (�
�4 �<� ����P ���K Syntax
------
CHANGE MASTER ['connection_name'] TO master_def [,
master_def] ...
master_def:
MASTER_BIND = 'interface_name'
| MASTER_HOST = 'host_name'[
| MASTER_USER = 'user_name'
| MASTER_PASSWORD = 'password'
| MASTER_PORT = port_num
| MASTER_CONNECT_RETRY = interval
| MASTER_HEARTBEAT_PERIOD = interval
| MASTER_LOG_FILE = 'master_log_name'
| MASTER_LOG_POS = master_log_pos
| RELAY_LOG_FILE = 'relay_log_name'
| RELAY_LOG_POS = relay_log_pos
| MASTER_DELAY = interval
| MASTER_SSL = {0|1}
| MASTER_SSL_CA = 'ca_file_name'
| MASTER_SSL_CAPATH = 'ca_directory_name'
| MASTER_SSL_CERT = 'cert_file_name'
| MASTER_SSL_CRL = 'crl_file_name'
| MASTER_SSL_CRLPATH = 'crl_directory_name'
| MASTER_SSL_KEY = 'key_file_name'
| MASTER_SSL_CIPHER = 'cipher_list'
| MASTER_SSL_VERIFY_SERVER_CERT = {0|1}
| MASTER_USE_GTID = {current_pos|slave_pos|no}
| IGNORE_SERVER_IDS = (server_id_list)
| DO_DOMAIN_IDS = ([N,..])
| IGNORE_DOMAIN_IDS = ([N,..])
Description
-----------
The CHANGE MASTER statement sets the options that a
replication slave uses to connect to and replicate from a
replication master.
MariaDB until 10.0.7
In MariaDB 10.0.7 and before, the relay_log_purge system
variable was silently set to 0 when CHANGE MASTER was
executed.
Multi-Source Replication
Multi-source replication was added in MariaDB 10.0.1.
If you are using multi-source replication, then you need to
specify a connection name when you execute CHANGE MASTER.
There are two ways to do this:
Setting the default_master_connection system variable prior
to executing CHANGE MASTER.
Setting the connection_name parameter when executing CHANGE
MASTER.
default_master_connection
SET default_master_connection = 'gandalf';
STOP SLAVE;
CHANGE MASTER TO
MASTER_PASSWORD='new3cret';
START SLAVE;
connection_name
STOP SLAVE 'gandalf';
CHANGE MASTER 'gandalf' TO
MASTER_PASSWORD='new3cret';
START SLAVE 'gandalf';
Options
Connection Options
MASTER_USER
The MASTER_USER option for CHANGE MASTER defines the user
account that the replication slave will use to connect to
the replication master.
This user account will need the REPLICATION SLAVE privilege
on the master.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_USER='repl',
MASTER_PASSWORD='new3cret';
START SLAVE;
MASTER_PASSWORD
The MASTER_USER option for CHANGE MASTER defines the
password that the replication slave will use to connect to
the replication master as the user account defined by the
MASTER_USER option.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_PASSWORD='new3cret';
START SLAVE;
MASTER_HOST
The MASTER_HOST option for CHANGE MASTER defines the
hostname or IP address of the replication master.
If you set the value of the MASTER_HOST option to the empty
string, then that is not the same as not setting the
option's value at all. In MariaDB 5.5 and later, if you set
the value of the MASTER_HOST option to the empty string,
then the CHANGE MASTER command will fail with an error. In
MariaDB 5.3 and before, if you set the value of the
MASTER_HOST option to the empty string, then the CHANGE
MASTER command would succeed, but the subsequent START SLAVE
command would fail.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_HOST='dbserver1.example.com',
MASTER_USER='repl',
MASTER_PASSWORD='new3cret',
MASTER_USE_GTID=slave_pos;
START SLAVE;
If you set the value of the MASTER_HOST option in a CHANGE
MASTER command, then the slave assumes that the master is
different from before, even if you set the value of this
option to the same value it had previously. In this
scenario, the slave will consider the old values for the
master's binary
log file name and position to be invalid for the new master.
As a side effect, if you do not explicitly set the values of
the MASTER_LOG_FILE and MASTER_LOG_POS options in the
statement, then the statement will be implicitly appended
with MASTER_LOG_FILE='' and MASTER_LOG_POS=4. However, if
you enable GTID mode for replication by setting the
MASTER_USE_GTID option to some value other than no in the
statement, then these values will effectively be ignored
anyway.
Replication slaves cannot connect to replication masters
using Unix socket files or Windows named pipes. The
replication slave must connect to the replication master
using TCP/IP.
MASTER_PORT
The MASTER_PORT option for CHANGE MASTER defines the TCP/IP
port of the replication master.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_HOST='dbserver1.example.com',
MASTER_PORT=3307,
MASTER_USER='repl',
MASTER_PASSWORD='new3cret',
MASTER_USE_GTID=slave_pos;
START SLAVE;
If you set the value of the MASTER_PORT option in a CHANGE
MASTER command, then the slave assumes that the master is
different from before, even if you set the value of this
option to the same value it had previously. In this
scenario, the slave will consider the old values for the
master's binary
log file name and position to be invalid for the new master.
As a side effect, if you do not explicitly set the values of
the MASTER_LOG_FILE and MASTER_LOG_POS options in the
statement, then the statement will be implicitly appended
with MASTER_LOG_FILE='' and MASTER_LOG_POS=4. However, if
you enable GTID mode for replication by setting the
MASTER_USE_GTID option to some value other than no in the
statement, then these values will effectively be ignored
anyway.
Replication slaves cannot connect to replication masters
using Unix socket files or Windows named pipes. The
replication slave must connect to the replication master
using TCP/IP.
MASTER_CONNECT_RETRY
The MASTER_CONNECT_RETRY option for CHANGE MASTER defines
how many seconds that the slave will wait between connection
retries. The default is 60.
STOP SLAVE;
CHANGE MASTER TO
MASTER_CONNECT_RETRY=20;
START SLAVE;
The number of connection attempts is limited by the
master_retry_count option. It can be set either on the
command-line or in a server option group in an option file
prior to starting up the server. For example:
[mariadb]
...
master_retry_count=4294967295
MASTER_BIND
The MASTER_BIND option for CHANGE MASTER is only supported
by MySQL 5.6.2 and later and by MySQL NDB Cluster 7.3.1 and
later. This option is not yet supported by MariaDB. See
MDEV-19248 for more information.
The MASTER_BIND option for CHANGE MASTER can be used on
replication slaves that have multiple network interfaces to
choose which network interface the slave will use to connect
to the master.
MASTER_HEARTBEAT_PERIOD
The MASTER_HEARTBEAT_PERIOD option for CHANGE MASTER can be
used to set the interval in seconds between replication
heartbeats. Whenever the master's binary log is updated
with an event, the waiting period for the next heartbeat is
reset.
This option's interval argument has the following
characteristics:
It is a decimal value with a range of 0 to 4294967 seconds.
It has a resolution of hundredths of a second.
Its smallest valid non-zero value is 0.001.
Its default value is the value of the slave_net_timeout
system variable divided by 2.
If it's set to 0, then heartbeats are disabled.
Heartbeats are sent by the master only if there are no
unsent events in the binary log file for a period longer
than the interval.
If the RESET SLAVE statement is executed, then the heartbeat
interval is reset to the default.
If the slave_net_timeout system variable is set to a value
that is lower than the current heartbeat interval, then a
warning will be issued.
TLS Options
The TLS options are used for providing information about
TLS. The options can be set even on slaves that are compiled
without TLS support. The TLS options are saved to either the
default master.info file or the file that is configured by
the master_info_file option, but these TLS options are
ignored unless the slave supports TLS.
See Replication with Secure Connections for more
information.
MASTER_SSL
The MASTER_SSL option for CHANGE MASTER tells the slave
whether to force TLS for the connection. The valid values
are 0 or 1.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_SSL=1;
START SLAVE;
MASTER_SSL_CA
The MAST)m� ER_SSL_CA option for CHANGE MASTER defines a path to
a PEM file that should contain one or more X509 certificates
for trusted Certificate Authorities (CAs) to use for TLS.
This option requires that you use the absolute path, not a
relative path. This option implies the MASTER_SSL option.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
MASTER_SSL_VERIFY_SERVER_CERT=1;
START SLAVE;
See Secure Connections Overview: Certificate Authorities
(CAs) for more information.
MASTER_SSL_CAPATH
The MASTER_SSL_CAPATH option for CHANGE MASTER defines a
path to a directory that contains one or more PEM files that
should each contain one X509 certificate for a trusted
Certificate Authority (CA) to use for TLS. This option
requires that you use the absolute path, not a relative
path. The directory specified by this option needs to be run
through the openssl rehash command. This option implies the
MASTER_SSL option.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
MASTER_SSL_CAPATH='/etc/my.cnf.d/certificates/ca/',
MASTER_SSL_VERIFY_SERVER_CERT=1;
START SLAVE;
See Secure Connections Overview: Certificate Authorities
(CAs) for more information.
MASTER_SSL_CERT
The MASTER_SSL_CERT option for CHANGE MASTER defines a path
to the X509 certificate file to use for TLS. This option
requires that you use the absolute path, not a relative
path. This option implies the MASTER_SSL option.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
MASTER_SSL_VERIFY_SERVER_CERT=1;
START SLAVE;
MASTER_SSL_CRL
The MASTER_SSL_CRL option for CHANGE MASTER defines a path
to a PEM file that should contain one or more revoked X509
certificates to use for TLS. This option requires that you
use the absolute path, not a relative path.
This option is only supported if the server was built with
OpenSSL. If the server was built with yaSSL, then this
option is not supported. See TLS and Cryptography Libraries
Used by MariaDB for more information about which libraries
are used on which platforms.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
MASTER_SSL_VERIFY_SERVER_CERT=1,
MASTER_SSL_CRL='/etc/my.cnf.d/certificates/crl.pem';
START SLAVE;
See Secure Connections Overview: Certificate Revocation
Lists (CRLs) for more information.
MASTER_SSL_CRLPATH
The MASTER_SSL_CRLPATH option for CHANGE MASTER defines a
path to a directory that contains one or more PEM files that
should each contain one revoked X509 certificate to use for
TLS. This option requires that you use the absolute path,
not a relative path. The directory specified by this
variable needs to be run through the openssl rehash command.
This option is only supported if the server was built with
OpenSSL. If the server was built with yaSSL, then this
option is not supported. See TLS and Cryptography Libraries
Used by MariaDB for more information about which libraries
are used on which platforms.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
MASTER_SSL_VERIFY_SERVER_CERT=1,
MASTER_SSL_CRLPATH='/etc/my.cnf.d/certificates/crl/';
START SLAVE;
See Secure Connections Overview: Certificate Revocation
Lists (CRLs) for more information.
MASTER_SSL_KEY
The MASTER_SSL_KEY option for CHANGE MASTER defines a path
to a private key file to use for TLS. This option requires
that you use the absolute path, not a relative path. This
option implies the MASTER_SSL option.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
MASTER_SSL_VERIFY_SERVER_CERT=1;
START SLAVE;
MASTER_SSL_CIPHER
The MASTER_SSL_CIPHER option for CHANGE MASTER defines the
list of permitted ciphers or cipher suites to use for TLS.
Besides cipher names, if MariaDB was compiled with OpenSSL,
this option could be set to "SSLv3" or "TLSv1.2" to
allow all SSLv3 or all TLSv1.2 ciphers. Note that the
TLSv1.3 ciphers cannot be excluded when using OpenSSL, even
by using this option. See Using TLSv1.3 for details. This
option implies the MASTER_SSL option.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
MASTER_SSL_VERIFY_SERVER_CERT=1,
MASTER_SSL_CIPHER='TLSv1.2';
START SLAVE;
MASTER_SSL_VERIFY_SERVER_CERT
The MASTER_SSL_VERIFY_SERVER_CERT option for CHANGE MASTER
enables server certificate verification. This option is
disabled by default.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_SSL_CERT='/etc/my.cnf.d/certificates/server-cert.pem',
MASTER_SSL_KEY='/etc/my.cnf.d/certificates/server-key.pem',
MASTER_SSL_CA='/etc/my.cnf.d/certificates/ca.pem',
MASTER_SSL_VERIFY_SERVER_CERT=1;
START SLAVE;
See Secure Connections Overview: Server Certificate
Verification for more information.
Binary Log Options
These options are related to the binary log position on the
master.
MASTER_LOG_FILE
The MASTER_LOG_FILE option for CHANGE MASTER can be used
along with MASTER_LOG_POS to specify the coordinates at
which the slave's I/O thread should begin reading from the
master's binary logs the next time the thread starts.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_LOG_FILE='master2-bin.001',
MASTER_LOG_POS=4;
START SLAVE;
The MASTER_LOG_FILE and MASTER_LOG_POS options cannot be
specified if the RELAY_LOG_FILE and RELAY_LOG_POS options
were also specified.
The MASTER_LOG_FILE and MASTER_LOG_POS options are
effectively ignored if you enable GTID mode for replication
by setting the MASTER_USE_GTID option to some value other
than no in the statement.
MASTER_LOG_POS
The MASTER_LOG_POS option for CHANGE MASTER can be used
along with MASTER_LOG_FILE to specify the coordinates at
which the slave's I/O thread should begin reading from the
master's binary logs the next time the thread starts.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_LOG_FILE='master2-bin.001',
MASTER_LOG_POS=4;
START SLAVE;
The MASTER_LOG_FILE and MASTER_LOG_POS options cannot be
specified if the RELAY_LOG_FILE and RELAY_LOG_POS options
were also specified.
The MASTER_LOG_FILE and MASTER_LOG_POS options are
effectively ignored if you enable GTID mode for replication
by setting the MASTER_USE_GTID option to some value other
than no in the statement.
Relay Log Options
These options are related to the relay log position on the
slave.
RELAY_LOG_FILE
The RELAY_LOG_FILE option for CHANGE MASTER can be used
along with the RELAY_LOG_POS option to specify the
coordinates at which the slave's SQL thread should begin
reading from the relay log the next time the thread starts.
The CHANGE MASTER statement usually deletes all relay log
files. However, if the RELAY_LOG_FILE and/or RELAY_LOG_POS
options are specified, then existing relay log files are
kept.
When you want to change the relay log position, you only
need to stop the slave's SQL thread. The slave's I/O
thread can continue running. The STOP SLAVE and START SLAVE
statements support the SQL_THREAD option for this scenario.
For example:
STOP SLAVE SQL_THREAD;
CHANGE MASTER TO
RELAY_LOG_FILE='slave-relay-bin.006',
RELAY_LOG_POS=4025;
START SLAVE SQL_THREAD;
When the value of this option is changed, theuT�: metadata about
the slave's SQL thread's position in the relay logs will
also be changed in the relay-log.info file or the file that
is configured by the relay_log_info_file system variable.
The RELAY_LOG_FILE and RELAY_LOG_POS options cannot be
specified if the MASTER_LOG_FILE and MASTER_LOG_POS options
were also specified.
RELAY_LOG_POS
The RELAY_LOG_POS option for CHANGE MASTER can be used along
with the RELAY_LOG_FILE option to specify the coordinates at
which the slave's SQL thread should begin reading from the
relay log the next time the thread starts.
The CHANGE MASTER statement usually deletes all relay log
files. However, if the RELAY_LOG_FILE and/or RELAY_LOG_POS
options are specified, then existing relay log files are
kept.
When you want to change the relay log position, you only
need to stop the slave's SQL thread. The slave's I/O
thread can continue running. The STOP SLAVE and START SLAVE
statements support the SQL_THREAD option for this scenario.
For example:
STOP SLAVE SQL_THREAD;
CHANGE MASTER TO
RELAY_LOG_FILE='slave-relay-bin.006',
RELAY_LOG_POS=4025;
START SLAVE SQL_THREAD;
When the value of this option is changed, the metadata about
the slave's SQL thread's position in the relay logs will
also be changed in the relay-log.info file or the file that
is configured by the relay_log_info_file system variable.
The RELAY_LOG_FILE and RELAY_LOG_POS options cannot be
specified if the MASTER_LOG_FILE and MASTER_LOG_POS options
were also specified.
GTID Options
MASTER_USE_GTID
The MASTER_USE_GTID option for CHANGE MASTER was first added
in MariaDB 10.0.2 to enable replication with Global
Transaction IDs (GTIDs).
The MASTER_USE_GTID option for CHANGE MASTER can be used to
configure the slave to use the global transaction ID (GTID)
when connecting to a master. The possible values are:
current_pos - Replicate in GTID mode and use
gtid_current_pos as the position to start downloading
transactions from the master.
slave_pos - Replicate in GTID mode and use gtid_slave_pos as
the position to start downloading transactions from the
master.
no - Don't replicate in GTID mode.
For example:
STOP SLAVE;
CHANGE MASTER TO
MASTER_USE_GTID = current_pos;
START SLAVE;
Or:
STOP SLAVE;
SET GLOBAL gtid_slave_pos='0-1-153';
CHANGE MASTER TO
MASTER_USE_GTID = slave_pos;
START SLAVE;
Replication Filter Options
IGNORE_SERVER_IDS
The IGNORE_SERVER_IDS option for CHANGE MASTER can be used
to configure a replication slave to ignore binary log events
that originated from certain servers. Filtered binary log
events will not get logged to the slave’s relay log, and
they will not be applied by the slave.
The option's value can be specified by providing a
comma-separated list of server_id values. For example:
STOP SLAVE;
CHANGE MASTER TO
IGNORE_SERVER_IDS = (3,5);
START SLAVE;
If you would like to clear a previously set list, then you
can set the value to an empty list. For example:
STOP SLAVE;
CHANGE MASTER TO
IGNORE_SERVER_IDS = ();
START SLAVE;
DO_DOMAIN_IDS
The DO_DOMAIN_IDS option for CHANGE MASTER was first added
in MariaDB 10.1.2.
The DO_DOMAIN_IDS option for CHANGE MASTER can be used to
configure a replication slave to only apply binary log
events if the transaction's GTID is in a specific
gtid_domain_id value. Filtered binary log events will not
get logged to the slave’s relay log, and they will not be
applied by the slave.
The option's value can be specified by providing a
comma-separated list of gtid_domain_id values. Duplicate
values are automatically ignored. For example:
STOP SLAVE;
CHANGE MASTER TO
DO_DOMAIN_IDS = (1,2);
START SLAVE;
If you would like to clear a previously set list, then you
can set the value to an empty list. For example:
STOP SLAVE;
CHANGE MASTER TO
DO_DOMAIN_IDS = ();
START SLAVE;
The DO_DOMAIN_IDS option and the IGNORE_DOMAIN_IDS option
cannot both be set to non-empty values at the same time. If
you want to set the DO_DOMAIN_IDS option, and the
IGNORE_DOMAIN_IDS option was previously set, then you need
to clear the value of the IGNORE_DOMAIN_IDS option. For
example:
STOP SLAVE;
CHANGE MASTER TO
IGNORE_DOMAIN_IDS = (),
DO_DOMAIN_IDS = (1,2);
START SLAVE;
The DO_DOMAIN_IDS option can only be specified if the slave
is replicating in GTID mode. Therefore, the MASTER_USE_GTID
option must also be set to some value other than no in order
to use this option.
IGNORE_DOMAIN_IDS
The IGNORE_DOMAIN_IDS option for CHANGE MASTER was first
added in MariaDB 10.1.2.
The IGNORE_DOMAIN_IDS option for CHANGE MASTER can be used
to configure a replication slave to ignore binary log events
if the transaction's GTID is in a specific gtid_domain_id
value. Filtered binary log events will not get logged to the
slave’s relay log, and they will not be applied by the
slave.
The option's value can be specified by providing a
comma-separated list of gtid_domain_id values. Duplicate
values are automatically ignored. For example:
STOP SLAVE;
CHANGE MASTER TO
IGNORE_DOMAIN_IDS = (1,2);
START SLAVE;
If you would like to clear a previously set list, then you
can set the value to an empty list. For example:
STOP SLAVE;
CHANGE MASTER TO
IGNORE_DOMAIN_IDS = ();
START SLAVE;
The DO_DOMAIN_IDS option and the IGNORE_DOMAIN_IDS option
cannot both be set to non-empty values at the same time. If
you want to set the IGNORE_DOMAIN_IDS option, and the
DO_DOMAIN_IDS option was previously set, then you need to
clear the value of the DO_DOMAIN_IDS option. For example:
STOP SLAVE;
CHANGE MASTER TO
DO_DOMAIN_IDS = (),
IGNORE_DOMAIN_IDS = (1,2);
START SLAVE;
The IGNORE_DOMAIN_IDS option can only be specified if the
slave is replicating in GTID mode. Therefore, the
MASTER_USE_GTID option must also be set to some value other
than no in order to use this option.
Delayed Replication Options
MASTER_DELAY
The MASTER_DELAY option for CHANGE MASTER was first added in
MariaDB 10.2.3 to enable delayed replication.
The MASTER_DELAY option for CHANGE MASTER can be used to
enable delayed replication. This option specifies the time
in seconds (at least) that a replication slave should lag
behind the master. Before executing an event, the slave will
first wait, if necessary, until the given time has passed
since the event was created on the master. The result is
that the slave will reflect the state of the master some
time back in the past. The default is zero, no delay.
STOP SLAVE;
CHANGE MASTER TO
MASTER_DELAY=3600;
START SLAVE;
Changing Option Values
If you don't specify a given option when executing the
CHANGE MASTER statement, then the option keeps its old value
in most cases. Most of the time, there is no need to specify
the options that do not need to change. For example, if the
password for the user account that the slave uses to connect
to its master has changed, but no other options need to
change, then you can just change the MASTER_PASSWORD option
by executing the following commands:
STOP SLAVE;
CHANGE MASTER TO
MASTER_PASSWORD='new3cret';
START SLAVE;
There are some cases where options are implicitly reset,
such as when the MASTER_HOST and MASTER_PORT options are
changed.
Option Persistence
The values of the MASTER_LOG_FILE and MASTER_LOG_POS options
(i.e. the binary log position on the master) and most other
options are written to either the default master.info file
or the file that is configured by the master_info_file
option. The slave's I/O thread keeps this binary log
position updated as it downloads events only when
MASTER_USE_GTID option
is set to NO. Otherwise the file is not updated on a per
event basis.
The master_info_file option can be set either on the
command-line or in a server option group in an option file
prior to starting up the server. For example:
[mariadb]
...
master_info_file=/mariadb/myserver1-master.info
The values of the RELAY_LOG_FILE and RELAY_LOG_POS options
(i.e. the relay log position) are written to either the
default relay-log.info file or the file that is configured
by the relay_log_info_file system variable. The slave's SQL
thread keeps this relay log ���� �; ` �! COMMITThe COMMIT statement ends a transaction, saving any changes
to the data so that they become visible to subsequent
transactions. Also, unlocks metadata changed by current
transaction. If autocommit is set to 1, an implicit commit
is performed after each statement. Otherwise, all
transactions which don't end with an explicit COMMIT are
implicitly rollbacked and the changes are lost. The ROLLBACK
statement can be used to do this explicitly.
The required syntax for the COMMIT statement is as follows:
COMMIT [WORK] [AND [NO] CHAIN] [[NO] RELEASE]
COMMIT is the more important transaction terminator, as well
as the more interesting one. The basic form of the COMMIT
statement is simply the keyword COMMIT (the keyword WORK is
simply noise and can be omitted without changing the
effect).
The optional AND CHAIN clause is a convenience for
initiating a new transaction as soon as the old transaction
terminates. If AND CHAIN is specified, then there is
effectively nothing between the old and new transactions,
although they remain separate. The characteristics of the
new transaction will be the same as the characteristics of
the old one — that is, the new transaction will have the
same access mode, isolation level and diagnostics area size
(we'll discuss all of these shortly) as the transaction
just terminated.
RELEASE tells the server to disconnect the client
immediately after the current transaction.
There are NO RELEASE and AND NO CHAIN options. By default,
commits do not RELEASE or CHAIN, but it's possible to
change this default behavior with the completion_type server
system variable. In this case, the AND NO CHAIN and NO
RELEASE options override the server default.
URL: https://mariadb.com/kb/en/commit/https://mariadb.com/kb/en/commit/ a e= DEALLOCATE / DROP PREPARESyntax
------
{DEALLOCATE | DROP} PREPARE stmt_name
Description
-----------
To deallocate a prepared statement produced with PREPARE,
use a
DEALLOCATE PREPARE statement that refers to the prepared
statement
name.
A prepared statement is implicitly deallocated when a new
PREPARE command is issued. In that case, there is no need to
use DEALLOCATE.
Attempting to execute a prepared statement after
deallocating it
results in an error, as if it was not prepared at all:
ERROR 1243 (HY000): Unknown prepared statement handler
(stmt_name) given to EXECUTE
If the specified statement has not been PREPAREd, an error
similar to the following will be produced:
ERROR 1243 (HY000): Unknown prepared statement handler
(stmt_name) given to DEALLOCATE PREPARE
Example
See example in PREPARE.
URL:
https://mariadb.com/kb/en/deallocate-drop-prepared-statement/https://mariadb.com/kb/en/deallocate-drop-prepared-statement/ b s, EXECUTE StatementSyntax
------
EXECUTE stmt_name
[USING expression[, expression] ...]
EXECUTE with expression as parameters was introduced in
MariaDB 10.2.3. Before that one could only use variables
(@var_name) as parameters.
Description
-----------
After preparing a statement with PREPARE, you execute it
with an
EXECUTE statement that refers to the prepared statement
name. If the
prepared statement contains any parameter markers, you must
supply a
USING clause that lists user variables containing the values
to be
bound to the parameters. Parameter values can be supplied
only by user
variables, and the USING clause must name exactly as many
variables as
the number of parameter markers in the statement.
You can execute a given prepared statement multiple times,
passing
different variables to it or setting the variables to
different values
before each execution.
If the specified statement has not been PREPAREd, an error
similar to the following is produced:
ERROR 1243 (HY000): Unknown prepared statement handler
(stmt_name) given to EXECUTE
Example
See example in PREPARE.
URL: https://mariadb.com/kb/en/execute-statement/https://mariadb.com/kb/en/execute-statement/ f �$ SAVEPOINTSyntax
------
SAVEPOINT identifier
ROLLBACK [WORK] TO [SAVEPOINT] identifier
RELEASE SAVEPOINT identifier
Description
-----------
InnoDB supports the SQL statements SAVEPOINT,
ROLLBACK TO SAVEPOINT, RELEASE SAVEPOINT
and the optional WORK keyword for
ROLLBACK.
Each savepoint must have a legal MariaDB identifier. A
savepoint is a named sub-transaction.
Normally ROLLBACK undoes the changes performed by the whole
transaction. When used with the TO clause, it undoes the
changes performed after the specified savepoint, and erases
all subsequent savepoints. However, all locks that have been
acquired after the save point will survive. RELEASE
SAVEPOINT does not rollback or commit any changes, but
removes the specified savepoint.
When the execution of a trigger or a stored function begins,
it is not possible to use statements which reference a
savepoint which was defined from out of that stored program.
When a COMMIT (including implicit commits) or a ROLLBACK
statement (with no TO clause) is performed, they act on the
whole transaction, and all savepoints are removed.
Errors
If COMMIT or ROLLBACK is issued and no transaction was
started, no error is reported.
If SAVEPOINT is issued and no transaction was started, no
error is reported but no savepoint is created. When ROLLBACK
TO SAVEPOINT or RELEASE SAVEPOINT is called for a savepoint
that does not exist, an error like this is issued:
ERROR 1305 (42000): SAVEPOINT svp_name does not exist
URL: https://mariadb.com/kb/en/savepoint/https://mariadb.com/kb/en/savepoint/� @ �y z
GRANT � � ST_XSyntax
------
ST_X(p)
X(p)
Description
-----------
Returns the X-coordinate value for the point p as a
double-precision number.
ST_X() and X() are synonyms.
Examples
--------
SET @pt = 'Point(56.7 53.34)';
SELECT X(GeomFromText(@pt));
+----------------------+
| X(GeomFromText(@pt)) |
+----------------------+
| 56.7 |
+----------------------+
URL: https://mariadb.com/kb/en/st_x/https://mariadb.com/kb/en/st_x/ � � ST_YSyntax
------
ST_Y(p)
Y(p)
Description
-----------
Returns the Y-coordinate value for the point p as a
double-precision number.
ST_Y() and Y() are synonyms.
Examples
--------
SET @pt = 'Point(56.7 53.34)';
SELECT Y(GeomFromText(@pt));
+----------------------+
| Y(GeomFromText(@pt)) |
+----------------------+
| 53.34 |
+----------------------+
URL: https://mariadb.com/kb/en/st_y/https://mariadb.com/kb/en/st_y/ � X - XA synonym for ST_X.
URL: https://mariadb.com/kb/en/point-properties-x/https://mariadb.com/kb/en/point-properties-x/ � X - YA synonym for ST_Y.
URL: https://mariadb.com/kb/en/point-properties-y/https://mariadb.com/kb/en/point-properties-y/ � +& AES_DECRYPTSyntax
------
AES_DECRYPT(crypt_str,key_str)
Description
-----------
This function allows decryption of data using the official
AES
(Advanced Encryption Standard) algorithm. For more
information, see
the description of AES_ENCRYPT().
URL: https://mariadb.com/kb/en/aes_decrypt/https://mariadb.com/kb/en/aes_decrypt/ � I! DECODESyntax
------
DECODE(crypt_str,pass_str)
Description
-----------
Decrypts the encrypted string crypt_str using pass_str as
the
password. crypt_str should be a string returned from
ENCODE(). The resulting string will be the original string
only if pass_str is the same.
URL: https://mariadb.com/kb/en/decode/https://mariadb.com/kb/en/decode/ ~�j� �� �����" �8�
�� q�I� �, c \, EXECUTE IMMEDIATEEXECUTE IMMEDIATE was introduced in MariaDB 10.2.3.
Syntax
------
EXECUTE IMMEDIATE statement
Description
-----------
EXECUTE IMMEDIATE executes a dynamic SQL statement created
on the fly, which can reduce performance overhead.
For example:
EXECUTE IMMEDIATE 'SELECT 1'
which is shorthand for:
prepare stmt from "select 1";
execute stmt;
deallocate prepare stmt;
EXECUTE IMMEDIATE supports complex expressions as prepare
source and parameters:
EXECUTE IMMEDIATE CONCAT('SELECT COUNT(*) FROM ', 't1',
' WHERE a=?') USING 5+5;
Limitations: subselects and stored function calls are not
supported as a prepare source.
The following examples return an error:
CREATE OR REPLACE FUNCTION f1() RETURNS VARCHAR(64) RETURN
'SELECT * FROM t1';
EXECUTE IMMEDIATE f1();
ERROR 1970 (42000): EXECUTE IMMEDIATE does not support
subqueries or stored functions
EXECUTE IMMEDIATE (SELECT 'SELECT * FROM t1');
ERROR 1064 (42000): You have an error in your SQL syntax;
check the manual that
corresponds to your MariaDB server version for the right
syntax to use near
'SELECT 'SELECT * FROM t1')' at line 1
CREATE OR REPLACE FUNCTION f1() RETURNS INT RETURN 10;
EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING f1();
ERROR 1970 (42000): EXECUTE..USING does not support
subqueries or stored functions
EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING
(SELECT 10);
ERROR 1064 (42000): You have an error in your SQL syntax;
check the manual that
corresponds to your MariaDB server version for the right
syntax to use near
'SELECT 10)' at line 1
One can use a user or an SP variable as a workaround:
CREATE OR REPLACE FUNCTION f1() RETURNS VARCHAR(64) RETURN
'SELECT * FROM t1';
SET @stmt=f1();
EXECUTE IMMEDIATE @stmt;
SET @stmt=(SELECT 'SELECT 1');
EXECUTE IMMEDIATE @stmt;
CREATE OR REPLACE FUNCTION f1() RETURNS INT RETURN 10;
SET @param=f1();
EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING
@param;
SET @param=(SELECT 10);
EXECUTE IMMEDIATE 'SELECT * FROM t1 WHERE a=?' USING
@param;
EXECUTE IMMEDIATE supports user variables and SP variables
as OUT parameters
DELIMITER $$
CREATE OR REPLACE PROCEDURE p1(OUT a INT)
BEGIN
SET a:= 10;
END;
$$
DELIMITER ;
SET @a=2;
EXECUTE IMMEDIATE 'CALL p1(?)' USING @a;
SELECT @a;
+------+
| @a |
+------+
| 10 |
+------+
Similar to PREPARE, EXECUTE IMMEDIATE is allowed in stored
procedures but is not allowed in stored functions.
This example uses EXECUTE IMMEDIATE inside a stored
procedure:
DELIMITER $$
CREATE OR REPLACE PROCEDURE p1()
BEGIN
EXECUTE IMMEDIATE 'SELECT 1';
END;
$$
DELIMITER ;
CALL p1;
+---+
| 1 |
+---+
| 1 |
+---+
This script returns an error:
DELIMITER $$
CREATE FUNCTION f1() RETURNS INT
BEGIN
EXECUTE IMMEDIATE 'DO 1';
RETURN 1;
END;
$$
ERROR 1336 (0A000): Dynamic SQL is not allowed in stored
function or trigger
EXECUTE IMMEDIATE can use DEFAULT and IGNORE indicators as
bind parameters:
CREATE OR REPLACE TABLE t1 (a INT DEFAULT 10);
EXECUTE IMMEDIATE 'INSERT INTO t1 VALUES (?)' USING
DEFAULT;
SELECT * FROM t1;
+------+
| a |
+------+
| 10 |
+------+
EXECUTE IMMEDIATE increments the Com_execute_immediate
status variable, as well as the Com_stmt_prepare,
Com_stmt_execute and Com_stmt_close status variables.
Note, EXECUTE IMMEDIATE does not increment the
Com_execute_sql status variable. Com_execute_sql is used
only for PREPARE..EXECUTE.
This session screenshot demonstrates how EXECUTE IMMEDIATE
affects status variables:
SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE
VARIABLE_NAME RLIKE
('COM_(EXECUTE|STMT_PREPARE|STMT_EXECUTE|STMT_CLOSE)');
+-----------------------+----------------+
| VARIABLE_NAME | VARIABLE_VALUE |
+-----------------------+----------------+
| COM_EXECUTE_IMMEDIATE | 0 |
| COM_EXECUTE_SQL | 0 |
| COM_STMT_CLOSE | 0 |
| COM_STMT_EXECUTE | 0 |
| COM_STMT_PREPARE | 0 |
+-----------------------+----------------+
EXECUTE IMMEDIATE 'SELECT 1';
+---+
| 1 |
+---+
| 1 |
+---+
SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE
VARIABLE_NAME RLIKE
('COM_(EXECUTE|STMT_PREPARE|STMT_EXECUTE|STMT_CLOSE)');
+-----------------------+----------------+
| VARIABLE_NAME | VARIABLE_VALUE |
+-----------------------+----------------+
| COM_EXECUTE_IMMEDIATE | 1 |
| COM_EXECUTE_SQL | 0 |
| COM_STMT_CLOSE | 1 |
| COM_STMT_EXECUTE | 1 |
| COM_STMT_PREPARE | 1 |
+-----------------------+----------------+
URL: https://mariadb.com/kb/en/execute-immediate/https://mariadb.com/kb/en/execute-immediate/ g + Metadata LockingMetadata locking has been supported since MariaDB 5.5. This
means that when a transaction (including XA transactions)
uses a table, it locks its metadata until the end of
transaction. Non-transactional tables are also locked, as
well as views and objects which are related to locked
tables/views (stored functions, triggers, etc). When a
connection tries to use a DDL statement (like an ALTER
TABLE) which modifies a table that is locked, that
connection is queued, and has to wait until it's unlocked.
Using savepoints and performing a partial rollback does not
release metadata locks.
LOCK TABLES ... WRITE are also queued. Some wrong statements
which produce an error may not need to wait for the lock to
be freed.
Metadata lock's timeout is determined by the value of the
lock_wait_timeout server system variable (in seconds).
However, note that its default value is 31536000 (1 year).
If this timeout exceeds, the following error is returned:
ERROR 1205 (HY000): Lock wait timeout exceeded;
try restarting transaction
If the metadata_lock_info plugin is installed, the
Information Schema metadata_lock_info table stores
information about existing metadata locks.
Example
Let's use the following MEMORY (non-transactional) table:
CREATE TABLE t (a INT) ENGINE = MEMORY;
Connection 1 starts a transaction, and INSERTs a row into t:
START TRANSACTION;
INSERT INTO t SET a=1;
t's metadata is now locked by connection 1. Connection 2
tries to alter t, but has to wait:
ALTER TABLE t ADD COLUMN b INT;
Connection 2's prompt is blocked now.
Now connection 1 ends the transaction:
COMMIT;
...and connection 2 finally gets the output of its command:
Query OK, 1 row affected (35.23 sec)
Records: 1 Duplicates: 0 Warnings: 0
URL: https://mariadb.com/kb/en/metadata-locking/https://mariadb.com/kb/en/metadata-locking/ � � MD5Syntax
------
MD5(str)
Description
-----------
Calculates an MD5 128-bit checksum for the string.
The return value is a 32-hex digit string, and as of MariaDB
5.5, is a nonbinary string in the connection character set
and collation, determined by the values of the
character_set_connection and collation_connection system
variables. Before 5.5, the return value was a binary string.
NULL is returned if the argument was NULL.
Examples
--------
SELECT MD5('testing');
+----------------------------------+
| MD5('testing') |
+----------------------------------+
| ae2b1fca515949e5d54fb22b8ed95575 |
+----------------------------------+
URL: https://mariadb.com/kb/en/md5/https://mariadb.com/kb/en/md5/ � �# PASSWORDSyntax
------
PASSWORD(str)
Description
-----------
The PASSWORD() function is used for hashing passwords for
use in authentication by the MariaDB server. It is not
intended for use in other applications.
Calculates and returns a hashed password string from the
plaintext password str. Returns an empty string (>= MariaDB
10.0.4) or NULL (
URL: https://mariadb.com/kb/en/password/https://mariadb.com/kb/en/password/ ���f �Ѧ2 � d �& LOCK TABLESSyntax
------
LOCK TABLE[S]
tbl_name [[AS] alias] lock_type
[, tbl_name [[AS] alias] lock_type] ...
[WAIT n|NOWAIT]
lock_type:
READ [LOCAL]
| [LOW_PRIORITY] WRITE
| WRITE CONCURRENT
UNLOCK TABLES
Description
-----------
The lock_type can be one of:
Option | Description |
READ | Read lock, no writes allowed |
READ LOCAL | Read lock, but allow concurrent inserts |
WRITE | Exclusive write lock. No other connections can read
or write to this table |
LOW_PRIORITY WRITE | Exclusive write lock, but allow new
read locks on the table until we get the write lock. |
WRITE CONCURRENT | Exclusive write lock, but allow READ
LOCAL locks to the table. |
MariaDB enables client sessions to acquire table locks
explicitly for the
purpose of cooperating with other sessions for access to
tables, or to
prevent other sessions from modifying tables during periods
when a
session requires exclusive access to them. A session can
acquire or
release locks only for itself. One session cannot acquire
locks for
another session or release locks held by another session.
Locks may be used to emulate transactions or to get more
speed when
updating tables.
LOCK TABLES explicitly acquires table locks for the current
client session.
Table locks can be acquired for base tables or views. To use
LOCK TABLES,
you must have the LOCK TABLES privilege, and the SELECT
privilege for
each object to be locked. See GRANT
For view locking, LOCK TABLES adds all base tables used in
the view to the
set of tables to be locked and locks them automatically. If
you lock a table
explicitly with LOCK TABLES, any tables used in triggers are
also locked
implicitly, as described in Triggers and Implicit Locks.
UNLOCK TABLES explicitly releases any table locks held by
the
current session.
WAIT/NOWAIT
Set the lock wait timeout. See WAIT and NOWAIT.
Limitations
LOCK TABLES doesn't work when using Galera cluster. You may
experience crashes or locks when used with Galera.
LOCK TABLES works on XtraDB/InnoDB tables only if the
innodb_table_locks system variable is set to 1 (the default)
and autocommit is set to 0 (1 is default). Please note that
no error message will be returned on LOCK TABLES with
innodb_table_locks = 0.
LOCK TABLES implicitly commits the active transaction, if
any. Also, starting a transaction always releases all table
locks acquired with LOCK TABLES. This means that there is no
way to have table locks and an active transaction at the
same time. The only exceptions are the transactions in
autocommit mode. To preserve the data integrity between
transactional and non-transactional tables, the GET_LOCK()
function can be used.
While a connection holds an explicit read lock on a table,
it cannot modify it. If you try, the following error will be
produced:
ERROR 1099 (HY000): Table 'tab_name' was locked with a
READ lock and can't be updated
While a connection holds an explicit lock on a table, it
cannot access a non-locked table. If you try, the following
error will be produced:
ERROR 1100 (HY000): Table 'tab_name' was not locked with
LOCK TABLES
While a connection holds an explicit lock on a table, it
cannot issue the following: INSERT DELAYED, CREATE TABLE,
CREATE TABLE ... LIKE, and DDL statements involving stored
programs and views (except for triggers). If you try, the
following error will be produced:
ERROR 1192 (HY000): Can't execute the given command because
you have active locked tables or an active transaction
LOCK TABLES can not be used in stored routines - if you try,
the following error will be produced on creation:
ERROR 1314 (0A000): LOCK is not allowed in stored procedures
URL: https://mariadb.com/kb/en/lock-tables/https://mariadb.com/kb/en/lock-tables/ i �, PURGE BINARY LOGSSyntax
------
PURGE { BINARY | MASTER } LOGS
{ TO 'log_name' | BEFORE datetime_expr }
Description
-----------
The PURGE BINARY LOGS statement deletes all the binary log
files listed in the log index file prior to the specified
log file name or
date. BINARY and MASTER are synonyms.
Deleted log files also are removed from the list recorded in
the index file, so
that the given log file becomes the first in the list.
The datetime expression is in the format 'YYYY-MM-DD
hh:mm:ss'.
If a slave is active but has yet to read from a binary log
file you attempt to delete, the statement will fail with an
error. However, if the slave is not connected and has yet to
read from a log file you delete, the file will be deleted,
but the slave will be unable to continue replicating once it
connects again.
This statement has no effect if the server was not started
with the
--log-bin option to enable binary logging.
To list the binary log files on the server, use SHOW BINARY
LOGS. To see which files they are reading, use SHOW SLAVE
STATUS. You can only delete the files that are older than
the oldest file that is used by the slaves.
To delete all binary log files, use RESET MASTER.
To move to a new log file (for example if you want to remove
the current log file), use FLUSH LOGS before you execute
PURGE LOGS.
If the expire_logs_days server system variable is not set to
0, the server automatically deletes binary log files after
the given number of days.
Examples
--------
PURGE BINARY LOGS TO 'mariadb-bin.000063';
PURGE BINARY LOGS BEFORE '2013-04-21';
PURGE BINARY LOGS BEFORE '2013-04-22 09:55:22';
URL: https://mariadb.com/kb/en/purge-binary-logs/https://mariadb.com/kb/en/purge-binary-logs/ � k 9
ENDPOINTA synonym for ST_ENDPOINT.
URL:
https://mariadb.com/kb/en/linestring-properties-endpoint/https://mariadb.com/kb/en/linestring-properties-endpoint/ � �"
GLENGTHSyntax
------
GLength(ls)
Description
-----------
Returns as a double-precision number the length of the
LineString value ls in its associated spatial reference.
Examples
--------
SET @ls = 'LineString(1 1,2 2,3 3)';
SELECT GLength(GeomFromText(@ls));
+----------------------------+
| GLength(GeomFromText(@ls)) |
+----------------------------+
| 2.82842712474619 |
+----------------------------+
URL: https://mariadb.com/kb/en/glength/https://mariadb.com/kb/en/glength/ � m :
NumPointsA synonym for ST_NumPoints.
URL:
https://mariadb.com/kb/en/linestring-properties-numpoints/https://mariadb.com/kb/en/linestring-properties-numpoints/ � g 7
PointNA synonym for ST_PointN.
URL: https://mariadb.com/kb/en/linestring-properties-pointn/https://mariadb.com/kb/en/linestring-properties-pointn/ �
o ;
STARTPOINTA synonym for ST_STARTPOINT.
URL:
https://mariadb.com/kb/en/linestring-properties-startpoint/https://mariadb.com/kb/en/linestring-properties-startpoint/ � &
ST_ENDPOINTSyntax
------
ST_EndPoint(ls)
EndPoint(ls)
Description
-----------
Returns the Point that is the endpoint of the
LineString value ls.
ST_EndPoint() and EndPoint() are synonyms.
Examples
--------
SET @ls = 'LineString(1 1,2 2,3 3)';
SELECT AsText(EndPoint(GeomFromText(@ls)));
+-------------------------------------+
| AsText(EndPoint(GeomFromText(@ls))) |
+-------------------------------------+
| POINT(3 3) |
+-------------------------------------+
URL: https://mariadb.com/kb/en/st_endpoint/https://mariadb.com/kb/en/st_endpoint/ �J�� � Z� b��� �� �`� � �� e T
# ROLLBACKThe ROLLBACK statement rolls back (ends) a transaction,
destroying any changes to SQL-data so that they never become
visible to subsequent transactions. The required syntax for
the ROLLBACK statement is as follows.
ROLLBACK [ WORK ] [ AND [ NO ] CHAIN ]
[ TO [ SAVEPOINT ] { | } ]
The ROLLBACK statement will either end a transaction,
destroying all data changes that happened during any of the
transaction, or it will just destroy any data changes that
happened since you established a savepoint. The basic form
of the ROLLBACK statement is just the keyword ROLLBACK (the
keyword WORK is simply noise and can be omitted without
changing the effect).
The optional AND CHAIN clause is a convenience for
initiating a new transaction as soon as the old transaction
terminates. If AND CHAIN is specified, then there is
effectively nothing between the old and new transactions,
although they remain separate. The characteristics of the
new transaction will be the same as the characteristics of
the old one — that is, the new transaction will have the
same access mode, isolation level and diagnostics area size
(we'll discuss all of these shortly) as the transaction
just terminated. The AND NO CHAIN option just tells your
DBMS to end the transaction — that is, these four SQL
statements are equivalent:
ROLLBACK;
ROLLBACK WORK;
ROLLBACK AND NO CHAIN;
ROLLBACK WORK AND NO CHAIN;
All of them end a transaction without saving any transaction
characteristics. The only other options, the equivalent
statements:
ROLLBACK AND CHAIN;
ROLLBACK WORK AND CHAIN;
both tell your DBMS to end a transaction, but to save that
transaction's characteristics for the next transaction.
ROLLBACK is much simpler than COMMIT: it may involve no more
than a few deletions (of Cursors, locks, prepared SQL
statements and log-file entries). It's usually assumed that
ROLLBACK can't fail, although such a thing is conceivable
(for example, an encompassing transaction might reject an
attempt to ROLLBACK because it's lining up for a COMMIT).
ROLLBACK cancels all effects of a transaction. It does not
cancel effects on objects outside the DBMS's control (for
example the values in host program variables or the settings
made by some SQL/CLI function calls). But in general, it is
a convenient statement for those situations when you say
"oops, this isn't working" or when you simply don't care
whether your temporary work becomes permanent or not.
Here is a moot question. If all you've been doing is
SELECTs, so that there have been no data changes, should you
end the transaction with ROLLBACK or COMMIT? It shouldn't
really matter because both ROLLBACK and COMMIT do the same
transaction-terminating job. However, the popular conception
is that ROLLBACK implies failure, so after a successful
series of SELECT statements the convention is to end the
transaction with COMMIT rather than ROLLBACK.
MariaDB (and most other DBMSs) supports rollback of SQL-data
change statements, but not of SQL-Schema statements. This
means that if you use any of CREATE, ALTER, DROP, GRANT,
REVOKE, you are implicitly committing at execution time.
INSERT INTO Table_2 VALUES(5);
DROP TABLE Table_3 CASCADE;
ROLLBACK;
The result will be that both the INSERT and the DROP will go
through as separate transactions so the ROLLBACK will have
no effect.
URL: https://mariadb.com/kb/en/rollback/https://mariadb.com/kb/en/rollback/ k �6 RESET SLAVERESET SLAVE ["connection_name"] [ALL]
RESET SLAVE makes the slave forget its replication position
in the
master's binary log. This statement is meant to be used for
a clean
start. It deletes the master.info and relay-log.info files,
all the
relay log files, and starts a new relay log file. To use
RESET SLAVE,
the slave replication threads must be stopped (use STOP
SLAVE if
necessary).
Note: All relay log files are deleted, even if they have not
been
completely executed by the slave SQL thread. (This is a
condition
likely to exist on a replication slave if you have issued a
STOP SLAVE
statement or if the slave is highly loaded.)
Connection information stored in the master.info file is
immediately
reset using any values specified in the corresponding
startup options.
This information includes values such as master host, master
port,
master user, and master password. If the slave SQL thread
was in the
middle of replicating temporary tables when it was stopped,
and RESET
SLAVE is issued, these replicated temporary tables are
deleted on the
slave.
The ALL also resets the PORT, HOST, USER and PASSWORD
parameters for the slave. If you are using a connection
name, it will permanently delete it and it will not show up
anymore in SHOW ALL SLAVES STATUS.
connection_name
The connection_name option was added as part of multi-source
replication added in MariaDB 10.0
If there is only one nameless master, or the default master
(as specified by the default_master_connection system
variable) is intended, connection_name can be omitted. If
provided, the RESET SLAVE statement will apply to the
specified master. connection_name is case-insensitive.
URL: https://mariadb.com/kb/en/reset-slave-connection_name/https://mariadb.com/kb/en/reset-slave-connection_name/ � �'
ST_NUMPOINTSSyntax
------
ST_NumPoints(ls)
NumPoints(ls)
Description
-----------
Returns the number of Point objects in the LineString
value ls.
ST_NumPoints() and NumPoints() are synonyms.
Examples
--------
SET @ls = 'LineString(1 1,2 2,3 3)';
SELECT NumPoints(GeomFromText(@ls));
+------------------------------+
| NumPoints(GeomFromText(@ls)) |
+------------------------------+
| 3 |
+------------------------------+
URL: https://mariadb.com/kb/en/st_numpoints/https://mariadb.com/kb/en/st_numpoints/ � $
ST_POINTNSyntax
------
ST_PointN(ls,N)
PointN(ls,N)
Description
-----------
Returns the N-th Point in the LineString value ls.
Points are numbered beginning with 1.
ST_PointN() and PointN() are synonyms.
Examples
--------
SET @ls = 'LineString(1 1,2 2,3 3)';
SELECT AsText(PointN(GeomFromText(@ls),2));
+-------------------------------------+
| AsText(PointN(GeomFromText(@ls),2)) |
+-------------------------------------+
| POINT(2 2) |
+-------------------------------------+
URL: https://mariadb.com/kb/en/st_pointn/https://mariadb.com/kb/en/st_pointn/ � U$ INET_ATONSyntax
------
INET_ATON(expr)
Description
-----------
Given the dotted-quad representation of an IPv4 network
address as a string,
returns an integer that represents the numeric value of the
address.
Addresses may be 4- or 8-byte addresses.
Returns NULL if the argument is not understood.
Examples
--------
SELECT INET_ATON('192.168.1.1');
+--------------------------+
| INET_ATON('192.168.1.1') |
+--------------------------+
| 3232235777 |
+--------------------------+
This is calculated as follows: 192 x 2563 + 168 x 256 2 + 1
x 256 + 1
URL: https://mariadb.com/kb/en/inet_aton/https://mariadb.com/kb/en/inet_aton/ � $ INET_NTOASyntax
------
INET_NTOA(expr)
Description
-----------
Given a numeric IPv4 network address in network byte order
(4 or 8 byte),
returns the dotted-quad representation of the address as a
string.
Examples
--------
SELECT INET_NTOA(3232235777);
+-----------------------+
| INET_NTOA(3232235777) |
+-----------------------+
| 192.168.1.1 |
+-----------------------+
192.168.1.1 corresponds to 3232235777 since 192 x 2563 + 168
x 256 2 + 1 x 256 + 1 = 3232235777
URL: https://mariadb.com/kb/en/inet_ntoa/https://mariadb.com/kb/en/inet_ntoa/ �<&��V�"�
�
]�� �Y h �, PREPARE StatementSyntax
------
PREPARE stmt_name FROM preparable_stmt
Description
-----------
The PREPARE statement prepares a statement and assigns it a
name,
stmt_name, by which to refer to the statement later.
Statement names
are not case sensitive. preparable_stmt is either a string
literal or a user variable (not a local variable, an SQL
expression or a subquery) that contains the text of the
statement. The text must
represent a single SQL statement, not multiple statements.
Within the
statement, "?" characters can be used as parameter markers
to indicate
where data values are to be bound to the query later when
you execute
it. The "?" characters should not be enclosed within
quotes, even if
you intend to bind them to string values. Parameter markers
can be used
only where data values should appear, not for SQL keywords,
identifiers, and so forth.
The scope of a prepared statement is the session within
which it is
created. Other sessions cannot see it.
If a prepared statement with the given name already exists,
it is
deallocated implicitly before the new statement is prepared.
This means
that if the new statement contains an error and cannot be
prepared, an
error is returned and no statement with the given name
exists.
Prepared statements can be PREPAREd and EXECUTEd in a stored
procedure, but not in a stored function or trigger. Also,
even if the statement is PREPAREd in a procedure, it will
not be deallocated when the procedure execution ends.
A prepared statement can access user-defined variables, but
not local variables or procedure's parameters.
If the prepared statement contains a syntax error, PREPARE
will fail. As a side effect, stored procedures can use it to
check if a statement is valid. For example:
CREATE PROCEDURE `test_stmt`(IN sql_text TEXT)
BEGIN
DECLARE EXIT HANDLER FOR SQLEXCEPTION
BEGIN
SELECT CONCAT(sql_text, ' is not valid');
END;
SET @SQL := sql_text;
PREPARE stmt FROM @SQL;
DEALLOCATE PREPARE stmt;
END;
The FOUND_ROWS() and ROW_COUNT() functions, if called
immediatly after EXECUTE, return the number of rows read or
affected by the prepared statements; however, if they are
called after DEALLOCATE PREPARE, they provide information
about this statement. If the prepared statement produces
errors or warnings, GET DIAGNOSTICS return information about
them. DEALLOCATE PREPARE shouldn't clear the diagnostics
area, unless it produces an error.
A prepared statement is executed with EXECUTE and released
with DEALLOCATE PREPARE.
The max_prepared_stmt_count server system variable
determines the number of allowed prepared statements that
can be prepared on the server. If it is set to 0, prepared
statements are not allowed. If the limit is reached, an
error similar to the following will be produced:
ERROR 1461 (42000): Can't create more than
max_prepared_stmt_count statements
(current value: 0)
Oracle Mode
In Oracle mode from MariaDB 10.3, PREPARE stmt FROM 'SELECT
:1, :2' is used, instead of ?.
Permitted Statements
Not all statements can be prepared. Only the following SQL
commands are permitted:
ALTER TABLE
ANALYZE TABLE
BINLOG
CACHE INDEX
CALL
CHANGE MASTER
CHECKSUM {TABLE | TABLES}
COMMIT
{CREATE | DROP} DATABASE
{CREATE | DROP} INDEX
{CREATE | RENAME | DROP} TABLE
{CREATE | RENAME | DROP} USER
{CREATE | DROP} VIEW
DELETE
DESCRIBE
DO
EXPLAIN
FLUSH {TABLE | TABLES | TABLES WITH READ LOCK | HOSTS |
PRIVILEGES | LOGS | STATUS |
MASTER | SLAVE | DES_KEY_FILE | USER_RESOURCES | QUERY
CACHE | TABLE_STATISTICS |
INDEX_STATISTICS | USER_STATISTICS | CLIENT_STATISTICS}
GRANT
INSERT
INSTALL {PLUGIN | SONAME}
HANDLER READ
KILL
LOAD INDEX INTO CACHE
OPTIMIZE TABLE
REPAIR TABLE
REPLACE
RESET {MASTER | SLAVE | QUERY CACHE}
REVOKE
ROLLBACK
SELECT
SET
SET GLOBAL SQL_SLAVE_SKIP_COUNTER
SET ROLE
SET SQL_LOG_BIN
SET TRANSACTION ISOLATION LEVEL
SHOW EXPLAIN
SHOW {DATABASES | TABLES | OPEN TABLES | TABLE STATUS |
COLUMNS | INDEX | TRIGGERS |
EVENTS | GRANTS | CHARACTER SET | COLLATION | ENGINES |
PLUGINS [SONAME] | PRIVILEGES |
PROCESSLIST | PROFILE | PROFILES | VARIABLES | STATUS |
WARNINGS | ERRORS |
TABLE_STATISTICS | INDEX_STATISTICS | USER_STATISTICS |
CLIENT_STATISTICS | AUTHORS |
CONTRIBUTORS}
SHOW CREATE {DATABASE | TABLE | VIEW | PROCEDURE | FUNCTION
| TRIGGER | EVENT}
SHOW {FUNCTION | PROCEDURE} CODE
SHOW BINLOG EVENTS
SHOW SLAVE HOSTS
SHOW {MASTER | BINARY} LOGS
SHOW {MASTER | SLAVE | TABLES | INNODB | FUNCTION |
PROCEDURE} STATUS
SLAVE {START | STOP}
TRUNCATE TABLE
SHUTDOWN
UNINSTALL {PLUGIN | SONAME}
UPDATE
Synonyms are not listed here, but can be used. For example,
DESC can be used instead of DESCRIBE.
Compound statements can be prepared too.
Note that if a statement can be run in a stored routine, it
will work even if it is called by a prepared statement. For
example, SIGNAL can't be directly prepared. However, it is
allowed in stored routines. If the x() procedure contains
SIGNAL, you can still prepare and execute the 'CALL x();'
prepared statement.
PREPARE now supports most kinds of expressions as well, for
example:
PREPARE stmt FROM CONCAT('SELECT * FROM ', table_name);
When PREPARE is used with a statement which is not
supported, the following error is produced:
ERROR 1295 (HY000): This command is not supported in the
prepared statement protocol yet
Example
create table t1 (a int,b char(10));
insert into t1 values (1,"one"),(2,
"two"),(3,"three");
prepare test from "select * from t1 where a=?";
set @param=2;
execute test using @param;
+------+------+
| a | b |
+------+------+
| 2 | two |
+------+------+
set @param=3;
execute test using @param;
+------+-------+
| a | b |
+------+-------+
| 3 | three |
+------+-------+
deallocate prepare test;
Since identifiers are not permitted as prepared statements
parameters, sometimes it is necessary to dynamically compose
an SQL statement. This technique is called dynamic SQL). The
following example shows how to use dynamic SQL:
CREATE PROCEDURE test.stmt_test(IN tab_name VARCHAR(64))
BEGIN
SET @sql = CONCAT('SELECT COUNT(*) FROM ', tab_name);
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
END;
CALL test.stmt_test('mysql.user');
+----------+
| COUNT(*) |
+----------+
| 4 |
+----------+
Use of variables in prepared statements:
PREPARE stmt FROM 'SELECT @x;';
SET @x = 1;
EXECUTE stmt;
+------+
| @x |
+------+
| 1 |
+------+
SET @x = 0;
EXECUTE stmt;
+------+
| @x |
+------+
| 0 |
+------+
DEALLOCATE PREPARE stmt;
URL: https://mariadb.com/kb/en/prepare-statement/https://mariadb.com/kb/en/prepare-statement/ � u' IS_FREE_LOCKSyntax
------
IS_FREE_LOCK(str)
Description
-----------
Checks whether the lock named str is free to use (that is,
not locked).
Returns 1 if the lock is free (no one is using the lock),
0 if the lock is in use, and NULL if an
error occurs (such as an incorrect argument, like an empty
string or NULL). str is case insensitive.
If the metadata_lock_info plugin is installed, the
Information Schema metadata_lock_info table contains
information about locks of this kind (as well as metadata
locks).
Statements using the IS_FREE_LOCK() function are not safe
for replication.
URL: https://mariadb.com/kb/en/is_free_lock/https://mariadb.com/kb/en/is_free_lock/ � �" IS_IPV6IS_IPV6() has been available since MariaDB 10.0.12.
Syntax
------
IS_IPV6(expr)
Description
-----------
Returns 1 if the expression is a valid IPv6 address
specified as a string, otherwise returns 0. Does not
consider IPv4 addresses to be valid IPv6 addresses.
Examples
--------
SELECT IS_IPV6('48f3::d432:1431:ba23:846f');
+--------------------------------------+
| IS_IPV6('48f3::d432:1431:ba23:846f') |
+--------------------------------------+
| 1 |
+--------------------------------------+
1 row in set (0.02 sec)
SELECT IS_IPV6('10.0.1.1');
+---------------------+
| IS_IPV6('10.0.1.1') |
+---------------------+
| 0 |
+---------------------+
URL: https://mariadb.com/kb/en/is_ipv6/https://mariadb.com/kb/en/is_ipv6/ � �� ��B� � l 2* SET TRANSACTIONSyntax
------
SET [GLOBAL | SESSION] TRANSACTION
transaction_property [, transaction_property] ...
transaction_property:
ISOLATION LEVEL level
| READ WRITE
| READ ONLY
level:
REPEATABLE READ
| READ COMMITTED
| READ UNCOMMITTED
| SERIALIZABLE
Description
-----------
This statement sets the transaction isolation level or the
transaction access mode globally, for the current session,
or for the next transaction:
With the GLOBAL keyword, the statement sets the default
transaction level globally for all subsequent sessions.
Existing sessions are
unaffected.
With the SESSION keyword, the statement sets the default
transaction level for all subsequent transactions performed
within the
current session.
Without any SESSION or GLOBAL keyword,
the statement sets the isolation level for the next (not
started) transaction
performed within the current session.
A change to the global default isolation level requires the
SUPER privilege. Any session is free to change its
session isolation level (even in the middle of a
transaction), or the isolation
level for its next transaction.
Isolation Level
To set the global default isolation level at server startup,
use the
--transaction-isolation=level option on the command line or
in an option file. Values of level for this option use
dashes
rather than spaces, so the allowable values are
READ-UNCOMMITTED,
READ-COMMITTED, REPEATABLE-READ, or
SERIALIZABLE. For example, to set the default isolation
level to REPEATABLE READ, use these lines in the [mysqld]
section of an option file:
[mysqld]
transaction-isolation = REPEATABLE-READ
To determine the global and session transaction isolation
levels at
runtime, check the value of the tx_isolation system
variable:
SELECT @@GLOBAL.tx_isolation, @@tx_isolation;
InnoDB supports each of the translation isolation levels
described here
using different locking strategies. The default level is
REPEATABLE READ. For additional information about InnoDB
record-level locks and how it uses them to execute various
types of statements,
see XtraDB/InnoDB Lock Modes,
and
http://dev.mysql.com/doc/refman/en/innodb-locks-set.html.
Isolation Levels
The following sections describe how MariaDB supports the
different transaction levels.
READ UNCOMMITTED
SELECT statements are performed in a non-locking fashion,
but a possible earlier version of a row might be used. Thus,
using this
isolation level, such reads are not consistent. This is also
called a "dirty
read." Otherwise, this isolation level works like
READ COMMITTED.
READ COMMITTED
A somewhat Oracle-like isolation level with respect to
consistent
(non-locking) reads: Each consistent read, even within the
same
transaction, sets and reads its own fresh snapshot. See
http://dev.mysql.com/doc/refman/en/innodb-consistent-read.html.
For locking reads (SELECT with FOR UPDATE
or LOCK IN SHARE MODE), InnoDB locks only index records, not
the gaps before them, and thus allows the free insertion of
new records next to
locked records. For UPDATE and DELETE
statements, locking depends on whether the statement uses a
unique index with a
unique search condition (such as WHERE id = 100), or a
range-type search condition (such as WHERE id > 100). For a
unique index with a unique search condition, InnoDB locks
only the index record
found, not the gap before it. For range-type searches,
InnoDB locks the index
range scanned, using gap locks or next-key (gap plus
index-record) locks to
block insertions by other sessions into the gaps covered by
the range. This is
necessary because "phantom rows" must be blocked for MySQL
replication and
recovery to work.
Note: Since MariaDB 5.1, if the READ COMMITTED isolation
level is used or the innodb_locks_unsafe_for_binlog system
variable is enabled,
there is no InnoDB gap locking except for foreign-key
constraint checking and
duplicate-key checking. Also, record locks for non-matching
rows are released
after MariaDB has evaluated the WHERE condition. As of
MariaDB/MySQL
5.1, if you use READ COMMITTED or enable
innodb_locks_unsafe_for_binlog, you must use row-based
binary logging.
REPEATABLE READ
This is the default isolation level for InnoDB. For
consistent reads,
there is an important difference from the READ COMMITTED
isolation level: All consistent reads within the same
transaction read the
snapshot established by the first read. This convention
means that if you issue
several plain (non-locking) SELECT statements within the
same transaction, these SELECT statements are consistent
also with respect to each other. See
http://dev.mysql.com/doc/refman/en/innodb-consistent-read.html.
For locking reads (SELECT with FOR UPDATE or LOCK IN SHARE
MODE),
UPDATE, and DELETE statements, locking depends on whether
the
statement uses a unique index with a unique search
condition, or a
range-type search condition. For a unique index with a
unique search
condition, InnoDB locks only the index record found, not the
gap
before it. For other search conditions, InnoDB locks the
index range
scanned, using gap locks or next-key (gap plus index-record)
locks to
block insertions by other sessions into the gaps covered by
the range.
This is the minimum isolation level for non-distributed XA
transactions.
SERIALIZABLE
This level is like REPEATABLE READ, but InnoDB implicitly
converts all
plain SELECT statements to SELECT ... LOCK IN SHARE MODE if
autocommit
is disabled. If autocommit is enabled, the SELECT is its own
transaction. It therefore is known to be read only and can
be
serialized if performed as a consistent (non-locking) read
and need
not block for other transactions. (This means that to force
a plain
SELECT to block if other transactions have modified the
selected rows,
you should disable autocommit.)
Distributed XA transactions should always use this isolation
level.
Access Mode
These clauses appeared in MariaDB 10.0.
The access mode specifies whether the transaction is allowed
to write data or not. By default, transactions are in READ
WRITE mode (see the tx_read_only system variable). READ ONLY
mode allows the storage engine to apply optimizations that
cannot be used for transactions which write data. The only
exception to this rule is that read only transactions can
perform DDL statements on temporary tables.
It is not permitted to specify both READ WRITE and READ ONLY
in the same statement.
READ WRITE and READ ONLY can also be specified in the START
TRANSACTION statement, in which case the specified mode is
only valid for one transaction.
Examples
--------
SET GLOBAL TRANSACTION ISOLATION LEVEL SERIALIZABLE;
Attempting to set the isolation level within an existing
transaction without specifying GLOBAL or SESSION.
START TRANSACTION;
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
ERROR 1568 (25001): Transaction characteristics can't be
changed while a transaction is in progress
URL: https://mariadb.com/kb/en/set-transaction/https://mariadb.com/kb/en/set-transaction/ � (' IS_USED_LOCKSyntax
------
IS_USED_LOCK(str)
Description
-----------
Checks whether the lock named str is in use (that is,
locked). If so,
it returns the connection identifier of the client that
holds the
lock. Otherwise, it returns NULL. str is case insensitive.
If the metadata_lock_info plugin is installed, the
Information Schema metadata_lock_info table contains
information about locks of this kind (as well as metadata
locks).
Statements using the IS_USED_LOCK() function are not safe
for replication.
URL: https://mariadb.com/kb/en/is_used_lock/https://mariadb.com/kb/en/is_used_lock/ �i yBF� �� m �& START SLAVESyntax
------
START SLAVE ["connection_name"] [thread_type [,
thread_type] ... ]
START SLAVE ["connection_name"] [SQL_THREAD] UNTIL
MASTER_LOG_FILE = 'log_name', MASTER_LOG_POS = log_pos
START SLAVE ["connection_name"] [SQL_THREAD] UNTIL
RELAY_LOG_FILE = 'log_name', RELAY_LOG_POS = log_pos
START SLAVE ["connection_name"] [SQL_THREAD] UNTIL
MASTER_GTID_POS =
START ALL SLAVES [thread_type [, thread_type]]
thread_type: IO_THREAD | SQL_THREAD
Description
-----------
START SLAVE with no thread_type options starts both of the
slave
threads (see replication). The I/O thread reads events from
the master server and stores
them in the relay log. The SQL thread reads events from the
relay log
and executes them. START SLAVE requires the SUPER privilege.
If START SLAVE succeeds in starting the slave threads, it
returns
without any error. However, even in that case, it might be
that the
slave threads start and then later stop (for example,
because they do
not manage to connect to the master or read its binary log,
or some
other problem). START SLAVE does not warn you about this.
You must
check the slave's error log for error messages generated by
the slave
threads, or check that they are running satisfactorily with
SHOW SLAVE
STATUS.
START SLAVE UNTIL
START SLAVE UNTIL refers to the SQL_THREAD slave position at
which the SQL_THREAD replication will halt. If SQL_THREAD
isn't specified both threads are started.
Since version 10.0.2, START SLAVE UNTIL master_gtid_pos=xxx
has also been supported. See Global Transaction ID/START
SLAVE UNTIL master_gtid_pos=xxx for more details.
connection_name
The connection_name option was added as part of multi-source
replication added in MariaDB 10.0
If there is only one nameless master, or the default master
(as specified by the default_master_connection system
variable) is intended, connection_name can be omitted. If
provided, the START SLAVE statement will apply to the
specified master. connection_name is case-insensitive.
START ALL SLAVES
START ALL SLAVES starts all configured slaves (slaves with
master_host not empty) that were not started before. It will
give a note for all started connections. You can check the
notes with SHOW WARNINGS.
URL: https://mariadb.com/kb/en/start-slave/https://mariadb.com/kb/en/start-slave/ n b, START TRANSACTIONSyntax
------
START TRANSACTION [transaction_property [,
transaction_property] ...] | BEGIN [WORK]
COMMIT [WORK] [AND [NO] CHAIN] [[NO] RELEASE]
ROLLBACK [WORK] [AND [NO] CHAIN] [[NO] RELEASE]
SET autocommit = {0 | 1}
transaction_property:
WITH CONSISTENT SNAPSHOT
| READ WRITE
| READ ONLY
Description
-----------
The START TRANSACTION or BEGIN statement
begins a new transaction. COMMIT commits the current
transaction, making its changes permanent. ROLLBACK rolls
back the current transaction, canceling its changes. The SET
autocommit statement disables or enables the default
autocommit mode for the current session.
START TRANSACTION and SET autocommit = 1 implicitly commit
the current transaction, if any.
The optional WORK keyword is supported for
COMMIT and ROLLBACK, as are the
CHAIN and RELEASE clauses.
CHAIN and RELEASE can be used for
additional control over transaction completion. The value of
the
completion_type system variable determines the default
completion behavior.
The AND CHAIN clause causes a new transaction to begin as
soon as the current one ends, and the new transaction has
the same isolation
level as the just-terminated transaction. The RELEASE clause
causes the server to disconnect the current client session
after terminating
the current transaction. Including the NO keyword suppresses
CHAIN or RELEASE completion, which can be
useful if the completion_type system variable is set to
cause chaining or release completion by default.
Access Mode
These clauses appeared in MariaDB 10.0.
The access mode specifies whether the transaction is allowed
to write data or not. By default, transactions are in READ
WRITE mode (see the tx_read_only system variable). READ ONLY
mode allows the storage engine to apply optimizations that
cannot be used for transactions which write data. The only
exception to this rule is that read only transactions can
perform DDL statements on temporary tables.
It is not permitted to specify both READ WRITE and READ ONLY
in the same statement.
READ WRITE and READ ONLY can also be specified in the SET
TRANSACTION statement, in which case the specified mode is
valid for all sessions, or for all subsequent transaction
used by the current session.
autocommit
By default, MariaDB runs with autocommit mode enabled. This
means that as soon as you execute a statement that updates
(modifies) a table, MariaDB stores the update on disk to
make it permanent. To disable autocommit mode, use the
following statement:
SET autocommit=0;
After disabling autocommit mode by setting the autocommit
variable to zero, changes to transaction-safe tables (such
as those for InnoDB or
NDBCLUSTER) are not made permanent immediately. You must use
COMMIT to store your changes to disk or ROLLBACK to ignore
the changes.
To disable autocommit mode for a single series of
statements, use the START TRANSACTION statement.
DDL Statements
DDL statements (CREATE, ALTER, DROP) and administrative
statements (FLUSH, RESET, OPTIMIZE, ANALYZE, CHECK, REPAIR,
CACHE INDEX), and LOAD DATA INFILE, cause an implicit COMMIT
and start a new transaction. An exception to this rule are
the DDL that operate on temporary tables: you can CREATE,
ALTER and DROP them without causing any COMMIT, but those
actions cannot be rolled back. This means that if you call
ROLLBACK, the temporary tables you created in the
transaction will remain, while the rest of the transaction
will be rolled back.
Transactions cannot be used in Stored Functions or Triggers.
In Stored Procedures and Events BEGIN is not allowed, so you
should use START TRANSACTION instead.
A transaction acquires a metadata lock on every table it
accesses to prevent other connections from altering their
structure. The lock is released at the end of the
transaction. This happens even with non-transactional
storage engines (like MEMORY or CONNECT), so it makes sense
to use transactions with non-transactional tables.
in_transaction
The in_transaction system variable appeared in MariaDB 5.3.
It is a session-only, read-only variable that returns 1
inside a transaction, and 0 if not in a transaction.
WITH CONSISTENT SNAPSHOT
The WITH CONSISTENT SNAPSHOT option starts a consistent read
for storage engines such as XtraDB and InnoDB that can do
so, the same as if a START TRANSACTION followed by a SELECT
from any InnoDB table was issued.
MariaDB 5.3 introduced enhancements to this feature. See
Enhancements for START TRANSACTION WITH CONSISTENT SNAPSHOT.
Examples
--------
START TRANSACTION;
SELECT @A:=SUM(salary) FROM table1 WHERE type=1;
UPDATE table2 SET summary=@A WHERE type=1;
COMMIT;
URL: https://mariadb.com/kb/en/start-transaction/https://mariadb.com/kb/en/start-transaction/ �
$% NAME_CONSTSyntax
------
NAME_CONST(name,value)
Description
-----------
Returns the given value. When used to produce a result set
column,
NAME_CONST() causes the column to have the given name. The
arguments should be constants.
This function is used internally when replicating stored
procedures. It makes little sense to use it explicitly in
SQL statements, and it was not supposed to be used like
that.
SELECT NAME_CONST('myname', 14);
+--------+
| myname |
+--------+
| 14 |
+--------+
URL: https://mariadb.com/kb/en/name_const/https://mariadb.com/kb/en/name_const/ �a- � ! �ؖ4 �� o
&% STOP SLAVESyntax
------
STOP SLAVE ["connection_name"] [thread_type [,
thread_type] ... ]
STOP ALL SLAVES [thread_type [, thread_type]]
thread_type: IO_THREAD | SQL_THREAD
Description
-----------
Stops the slave threads. STOP SLAVE requires the SUPER
privilege.
Like START SLAVE, this statement may be used with the
IO_THREAD and
SQL_THREAD options to name the thread or threads to be
stopped. In almost all cases, one never need to use the
thread_type options.
STOP SLAVE waits until any current replication event group
affecting
one or more non-transactional tables has finished executing
(if there
is any such replication group), or until the user issues a
KILL QUERY or KILL CONNECTION statement.
Note that STOP SLAVE doesn't delete the connection
permanently. Next time you execute START SLAVE or the
MariaDB server restarts, the slave connection is restored
with it's original arguments. If you want to delete a
connection, you should execute RESET SLAVE.
STOP ALL SLAVES
STOP ALL SLAVES stops all your running slaves. It will give
you a note for every stopped connection. You can check the
notes with SHOW WARNINGS.
connection_name
The connection_name option was added as part of multi-source
replication added in MariaDB 10.0
If there is only one nameless master, or the default master
(as specified by the default_master_connection system
variable) is intended, connection_name can be omitted. If
provided, the STOP SLAVE statement will apply to the
specified master. connection_name is case-insensitive.
URL: https://mariadb.com/kb/en/stop-slave/https://mariadb.com/kb/en/stop-slave/ p / Transaction TimeoutsMariaDB has always had the wait_timeout and
interactive_timeout settings, which close connections after
a certain period of inactivity.
However, these are by default set to a long wait period. In
situations where transactions may be started, but not
committed or rolled back, more granular control and a
shorter timeout may be desirable so as to avoid locks being
held for too long.
MariaDB 10.3 introduced three new variables to handle this
situation.
idle_transaction_timeout (all transactions)
idle_write_transaction_timeout (write transactions - called
idle_readwrite_transaction_timeout until MariaDB 10.3.2)
idle_readonly_transaction_timeout (read transactions)
These accept a time in seconds to time out, by closing the
connection, transactions that are idle for longer than this
period. By default all are set to zero, or no timeout.
idle_transaction_timeout affects all transactions,
idle_write_transaction_timeout affects write transactions
only and idle_readonly_transaction_timeout affects read
transactions only. The latter two variables work
independently. However, if either is set along with
idle_transaction_timeout, the settings for
idle_write_transaction_timeout or
idle_readonly_transaction_timeout will take precedence.
Examples
--------
SET SESSION idle_transaction_timeout=2;
BEGIN;
SELECT * FROM t;
Empty set (0.000 sec)
## wait 3 seconds
SELECT * FROM t;
ERROR 2006 (HY000): MySQL server has gone away
SET SESSION idle_write_transaction_timeout=2;
BEGIN;
SELECT * FROM t;
Empty set (0.000 sec)
## wait 3 seconds
SELECT * FROM t;
Empty set (0.000 sec)
INSERT INTO t VALUES(1);
## wait 3 seconds
SELECT * FROM t;
ERROR 2006 (HY000): MySQL server has gone away
SET SESSION idle_transaction_timeout=2, SESSION
idle_readonly_transaction_timeout=10;
BEGIN;
SELECT * FROM t;
Empty set (0.000 sec)
## wait 3 seconds
SELECT * FROM t;
Empty set (0.000 sec)
## wait 11 seconds
SELECT * FROM t;
ERROR 2006 (HY000): MySQL server has gone away
URL: https://mariadb.com/kb/en/transaction-timeouts/https://mariadb.com/kb/en/transaction-timeouts/ r �* WAIT and NOWAITMariaDB 10.3.0 introduced extended syntax so that it is
possible to set innodb_lock_wait_timeout and
lock_wait_timeout for the following statements:
Syntax
------
ALTER TABLE tbl_name [WAIT n|NOWAIT] ...
CREATE ... INDEX ON tbl_name (index_col_name, ...) [WAIT
n|NOWAIT] ...
DROP INDEX ... [WAIT n|NOWAIT]
DROP TABLE tbl_name [WAIT n|NOWAIT] ...
LOCK TABLE ... [WAIT n|NOWAIT]
OPTIMIZE TABLE tbl_name [WAIT n|NOWAIT]
RENAME TABLE tbl_name [WAIT n|NOWAIT] ...
SELECT ... FOR UPDATE [WAIT n|NOWAIT]
SELECT ... LOCK IN SHARE MODE [WAIT n|NOWAIT]
TRUNCATE TABLE tbl_name [WAIT n|NOWAIT]
Description
-----------
The lock wait timeout can be explicitly set in the statement
by using either WAIT n (to set the wait in seconds) or
NOWAIT, in which case the statement will immediately fail if
the lock cannot be obtained. WAIT 0 is equivalent to NOWAIT.
URL: https://mariadb.com/kb/en/wait-and-nowait/https://mariadb.com/kb/en/wait-and-nowait/ t J*
Account LockingAccount locking was introduced in MariaDB 10.4.2.
Description
-----------
Account locking permits privileged administrators to
lock/unlock user accounts. No new client connections will be
permitted if an account is locked (existing connections are
not affected).
User accounts can be locked at creation, with the CREATE
USER statement, or modified after creation with the ALTER
USER statement. For example:
CREATE USER 'lorin'@'localhost' ACCOUNT LOCK;
or
ALTER USER 'marijn'@'localhost' ACCOUNT LOCK;
The server will return an ER_ACCOUNT_HAS_BEEN_LOCKED error
when locked users attempt to connect:
mysql -ulorin
ERROR 4151 (HY000): Access denied, this account is locked
The ALTER USER statement is also used to unlock a user:
ALTER USER 'lorin'@'localhost' ACCOUNT UNLOCK;
The SHOW CREATE USER statement will show whether the account
is locked:
SHOW CREATE USER 'marijn'@'localhost';
+-----------------------------------------------+
| CREATE USER for marijn@localhost |
+-----------------------------------------------+
| CREATE USER 'marijn'@'localhost' ACCOUNT LOCK |
+-----------------------------------------------+
as well as querying the mysql.global_priv table:
SELECT CONCAT(user, '@', host, ' => ',
JSON_DETAILED(priv)) FROM mysql.global_priv
WHERE user='marijn';
+--------------------------------------------------------------------------------------+
| CONCAT(user, '@', host, ' => ', JSON_DETAILED(priv)) |
+--------------------------------------------------------------------------------------+
| marijn@localhost => {
"access": 0,
"plugin": "mysql_native_password",
"authentication_string": "",
"account_locked": true,
"password_last_changed": 1558017158
} |
+--------------------------------------------------------------------------------------+
URL: https://mariadb.com/kb/en/account-locking/https://mariadb.com/kb/en/account-locking/ � � SLEEPSyntax
------
SLEEP(duration)
Description
-----------
Sleeps (pauses) for the number of seconds given by the
duration argument, then
returns 0. If SLEEP() is interrupted, it
returns 1. The duration may have a fractional part given in
microseconds.
Statements using the SLEEP() function are not safe for
replication.
Example
SELECT SLEEP(5.5);
+------------+
| SLEEP(5.5) |
+------------+
| 0 |
+------------+
1 row in set (5.50 sec)
URL: https://mariadb.com/kb/en/sleep/https://mariadb.com/kb/en/sleep/ �
�% UUID_SHORTSyntax
------
UUID_SHORT()
Description
-----------
Returns a "short" universal identifier as a 64-bit
unsigned integer (rather
than a string-form 128-bit identifier as returned by the
UUID() function).
The value of UUID_SHORT() is guaranteed to be unique if the
following conditions hold:
The server_id of the current host is unique among your set
of master and
slave servers
server_id is between 0 and 255
You don't set back your system time for your server between
mysqld restarts
You do not invoke UUID_SHORT() on average more than 16
million times per second between mysqld restarts
The UUID_SHORT() return value is constructed this way:
(server_id & 255)
URL: https://mariadb.com/kb/en/uuid_short/https://mariadb.com/kb/en/uuid_short/ X
3%����of c��~U Overview
The MariaDB XA implementation is based on the X/Open CAE
document Distributed Transaction Processing: The XA
Specification. This document is published by The Open Group
and available at
http://www.opengroup.org/public/pubs/catalog/c193.htm.
XA transactions are designed to allow distributed
transactions, where a transaction manager (the application)
controls a transaction which involves multiple resources.
Such resources are usually DBMSs, but could be resources of
any type. The whole set of required transactional operations
is called a global transaction. Each subset of operations
which involve a single resource is called a local
transaction. XA used a 2-phases commit (2PC). With the first
commit, the transaction manager tells each resource to
prepare an effective commit, and waits for a confirm
message. The changes are not still made effective at this
point. If any of the resources encountered an error, the
transaction manager will rollback the global transaction. If
all resources communicate that the first commit is
successful, the transaction manager can require a second
commit, which makes the changes effective.
In MariaDB, XA transactions can only be used with storage
engines that support them. At least InnoDB, TokuDB, SPIDER
and MyRocks support them. For InnoDB, XA transactions can be
disabled by setting the innodb_support_xa server system
variable to 0.
Like regular transactions, XA transactions create metadata
locks on accessed tables.
XA transactions require REPEATABLE READ as a minimum
isolation level. However, distributed transactions should
always use SERIALIZABLE.
Trying to start more than one XA transaction at the same
time produces a 1400 error (SQLSTATE 'XAE09'). The same
error is produced when attempting to start an XA transaction
while a regular transaction is in effect. Trying to start a
regular transaction while an XA transaction is in effect
produces a 1399 error (SQLSTATE 'XAE07').
The statements that cause an implicit COMMIT for regular
transactions produce a 1400 error (SQLSTATE 'XAE09') if a
XA transaction is in effect.
Internal XA vs External XA
XA transactions are an overloaded term in MariaDB. If a
storage engine is XA-capable, it can mean one or both of
these:
It supports MariaDB's internal two-phase commit API. This
is transparent to the user. Sometimes this is called
"internal XA", since MariaDB's internal transaction
coordinator log can handle coordinating these transactions.
It supports XA transactions, with the XA START, XA PREPARE,
XA COMMIT, etc. statements. Sometimes this is called
"external XA", since it requires the use of an external
transaction coordinator to use this feature properly.
Transaction Coordinator Log
If you have two or more XA-capable storage engines enabled,
then a transaction coordinator log must be available.
There are currently two implementations of the transaction
coordinator log:
Binary log-based transaction coordinator log
Memory-mapped file-based transaction coordinator log
If the binary log is enabled on a server, then the server
will use the binary log-based transaction coordinator log.
Otherwise, it will use the memory-mapped file-based
transaction coordinator log.
See Transaction Coordinator Log for more information.
Syntax
------
XA {START|BEGIN} xid [JOIN|RESUME]
XA END xid [SUSPEND [FOR MIGRATE]]
XA PREPARE xid
XA COMMIT xid [ONE PHASE]
XA ROLLBACK xid
XA RECOVER [FORMAT=['RAW'|'SQL']]
xid: gtrid [, bqual [, formatID ]]
The interface to XA transactions is a set of SQL statements
starting with XA. Each statement changes a transaction's
state, determining which actions it can perform. A
transaction which does not exist is in the NON-EXISTING
state.
XA START (or BEGIN) starts a transaction and defines its xid
(a transaction identifier). The JOIN or RESUME keywords have
no effect. The new transaction will be in ACTIVE state.
The xid can have 3 components, though only the first one is
mandatory. gtrid is a quoted string representing a global
transaction identifier. bqual is a quoted string
representing a local transaction identifier. formatID is an
unsigned integer indicating the format used for the first
two components; if not specified, defaults to 1. MariaDB
does not interpret in any way these components, and only
uses them to identify a transaction. xids of transactions in
effect must be unique.
XA END declares that the specified ACTIVE transaction is
finished and it changes its state to IDLE. SUSPEND [FOR
MIGRATE] has no effect.
XA PREPARE prepares an IDLE transaction for commit, changing
its state to PREPARED. This is the first commit.
XA COMMIT definitely commits and terminates a transaction
which has already been PREPARED. If the ONE PHASE clause is
specified, this statements performs a 1-phase commit on an
IDLE transaction.
XA ROLLBACK rolls back and terminates an IDLE or PREPARED
transaction.
XA RECOVER shows information about all PREPARED
transactions.
When trying to execute an operation which is not allowed for
the transaction's current state, an error is produced:
XA COMMIT 'test' ONE PHASE;
ERROR 1399 (XAE07): XAER_RMFAIL: The command cannot be
executed when global transaction is in the ACTIVE state
XA COMMIT 'test2';
ERROR 1399 (XAE07): XAER_RMFAIL: The command cannot be
executed when global transaction is in the NON-EXISTING
state
XA RECOVER
The XA RECOVER statement shows information about all
transactions which are in the PREPARED state. It does not
matter which connection created the transaction: if it has
been PREPARED, it appears. But this does not mean that a
connection can commit or rollback a transaction which was
started by another connection. Note that transactions using
a 1-phase commit are never in the PREPARED state, so they
cannot be shown by XA RECOVER.
XA RECOVER produces four columns:
XA RECOVER;
+----------+--------------+--------------+------+
| formatID | gtrid_length | bqual_length | data |
+----------+--------------+--------------+------+
| 1 | 4 | 0 | test |
+----------+--------------+--------------+------+
You can use XA RECOVER FORMAT='SQL' to get the data in a
human readable
form that can be directly copy-pasted into XA COMMIT or XA
ROLLBACK. This is particularly useful for binary xid
generated by some transaction coordinators.
formatID is the formatID part of xid.
data are the gtrid and bqual parts of xid, concatenated.
gtrid_length and bqual_length are the lengths of gtrid and
bqual, respectevely.
Examples
--------
2-phases commit:
XA START 'test';
INSERT INTO t VALUES (1,2);
XA END 'test';
XA PREPARE 'test';
XA COMMIT 'test';
1-phase commit:
XA START 'test';
INSERT INTO t VALUES (1,2);
XA END 'test';
XA COMMIT 'test' ONE PHASE;
Human-readable:
xa start '12\r34\t67\v78', 'abc\ndef', 3;
insert t1 values (40);
xa end '12\r34\t67\v78', 'abc\ndef', 3;
xa prepare '12\r34\t67\v78', 'abc\ndef', 3;
xa recover format='RAW';
+----------+--------------+--------------+--------------------+
| formatID | gtrid_length | bqual_length | data |
+----------+--------------+--------------+--------------------+
34 67v78abc 11 | 7 | 12
def |
+----------+--------------+--------------+--------------------+
xa recover format='SQL';
+----------+--------------+--------------+-----------------------------------------------+
| formatID | gtrid_length | bqual_length | data |
+----------+--------------+--------------+-----------------------------------------------+
| 3 | 11 | 7 |
X'31320d3334093637763738',X'6162630a646566',3 |
+----------+--------------+--------------+-----------------------------------------------+
xa rollback
X'31320d3334093637763738',X'6162630a646566',3;
Known Issues
MariaDB Galera Cluster
MariaDB Galera Cluster does not support XA transactions. See
MDEV-10532 for more information on that. The request to
implement that feature is being tracked at MDEV-17099.
However, MariaDB Galera Cluster builds include a built-in
plugin called wsrep. Prior to MariaDB 10.4.3, this plugin
was internally considered an XA-capable storage engine.
Consequently, these MariaDB Galera Cluster builds have
mu"�� MariaDB 10.4 introduces a number of changes to the
authentication process, intended to make things easier and
more intuitive.
Overview
There are four main changes relating to authentication:
It is possible to use more than one authentication plugin
for each user account. For example, this can be useful to
slowly migrate users to the more secure ed25519
authentication plugin over time, while allowing the old
mysql_native_password authentication plugin as an
alternative for the transitional period.
The root@localhost user account created by mysql_install_db
is created with the ability to use two authentication
plugins.
First, it is configured to try to use the unix_socket
authentication plugin. This allows the the root@localhost
user to login without a password via the local Unix socket
file defined by the socket system variable, as long as the
login is attempted from a process owned by the operating
system root user account.
Second, if authentication fails with the unix_socket
authentication plugin, then it is configured to try to use
the mysql_native_password authentication plugin. However, an
invalid password is initially set, so in order to
authenticate this way, a password must be set with SET
PASSWORD.
However, just using the unix_socket authentication plugin
may be fine for many users, and it is very secure. You may
want to try going without password authentication to see how
well it works for you. Remember, the best way to keep your
password safe is not to have one!
All user accounts, passwords, and global privileges are now
stored in the mysql.global_priv table. The mysql.user table
still exists and has exactly the same set of columns as
before, but it’s now a view that references the
mysql.global_priv table. Tools that analyze the mysql.user
table should continue to workas before.
MariaDB 10.4 supports User Password Expiry, which is not
active by default.
Description
-----------
As a result of the above changes, the open-for-everyone
all-powerful root account is finally gone. And installation
scripts will no longer demand that you “PLEASE REMEMBER TO
SET A PASSWORD FOR THE MariaDB root USER !”, because the
root account is securely created automatically.
Two all-powerful accounts are created by default — root
and the OS user that owns the data directory, typically
mysql. They are created as:
CREATE USER root@localhost IDENTIFIED VIA unix_socket OR
mysql_native_password USING 'invalid'
CREATE USER mysql@localhost IDENTIFIED VIA unix_socket OR
mysql_native_password USING 'invalid'
Using unix_socket means that if you are the system root
user, you can login as root@locahost without a password.
This technique was pioneered by Otto Kekäläinen in Debian
MariaDB packages and has been successfully used in Debian
since as early as MariaDB 10.0.
It is based on a simple fact that asking the system root for
a password adds no extra security — root has full access
to all the data files and all process memory anyway. But not
asking for a password means, there is no root password to
forget (no need for the numerous tutorials on “how to
reset MariaDB root password”). And if you want to script
some tedious database work, there is no need to store the
root password in plain text for the scipt to use (no need
for debian-sys-maint user).
Still, some users may wish to log in as MariaDB root without
using sudo. Hence the old authentication method —
conventional MariaDB password — is still available. By
default it is disabled (“invalid” is not a valid
password hash), but one can set the password with a usual
SET PASSWORD statement. And still retain the password-less
access via sudo.
If you install MariaDB locally (say from a tarball, you
would not want to use sudo to be able to login. This is why
MariaDB creates a second all-powerful user with the same
name as a system user that owns the data directory. In local
(not system-wide) installations, this will be the user who
installed MariaDB — they automatically get convenient
password-less root-like access, because they can access all
the data files anyway.
Even if MariaDB is installed system-wide, you may not want
to run your database maintenance scripts as system root —
now you can run them as system mysql user. And you will know
that they will never destroy your entire system, even if you
make a typo in a shell script.
However, seasoned MariaDB DBAs who are used to the old ways
do need to makes some changes. See the examples below for
common tasks.
Cookbook
After installing MariaDB system-wide the first thing
you’ve got used to doing is logging in into the
unprotected root account and protecting it, that is, setting
the root password:
$ sudo dnf install MariaDB-server
$ mysql -uroot
...
MariaDB> set password = password("XH4VmT3_jt");
This is not only unnecessary now, it will simply not work
— there is no unprotected root account. To login as root
use
$ sudo dnf install MariaDB-server
$ sudo mysql
Note that it implies you are connecting via the unix socket,
not tcp. If you happen to have protocol=tcp in a system-wide
/etc/my.cnf file, use sudo mysql --protocol=socket.
After installing MariaDB locally you’ve also used to
connect to the unprotected root account using mysql -uroot.
This will not work either, simply use mysql without
specifying a username.
If you've forgotten your root password, no problem — you
can still connect using sudo and change the password. And if
you've also removed unix_socket authentication, to restore
access do as follows:
restart MariaDB with --skip-grant-tables
login into the unprotected server
run FLUSH PRIVILEGES (note, before 10.4 this would’ve been
the last step, not anymore). This disables
--skip-grant-tables and allows you to change the stored
authentication method.
run SET PASSWORD FOR root@localhost to change the root
password
To view inside privilege tables, the old mysql.user table
still exists. You can select from it as before, although you
cannot update it anymore. It doesn’t show alternative
authentication plugins and this was one of the reasons for
switching to the mysql.global_priv table — complex
authentication rules did not fit into rigid structure of a
relational table. You can select from the new table, for
example:
select concat(user, '@', host, ' => ',
json_detailed(priv)) from mysql.global_priv;
Reverting to the Previous Authentication Method for
root@localhost
If you don't want the root@localhost user account created
by mysql_install_db to use unix_socket authentication by
default, then there are a few ways to revert to the previous
mysql_native_password authentication method for this user
account.
Configuring mysql_install_db to Revert to the Previous
Authentication Method
One way to revert to the previous mysql_native_password
authentication method for the root@localhost user account is
to execute mysql_install_db with a special option. If
mysql_install_db is executed while
--auth-root-authentication-method=normal is specified, then
it will create the default user accounts using the default
behavior of MariaDB 10.3 and before.
This means that the root@localhost user account will use
mysql_native_password authentication by default. There are
some other differences as well. See mysql_install_db: User
Accounts Created by Default for more information.
For example, the option can be set on the command-line while
running mysql_install_db:
mysql_install_db --user=mysql --datadir=/var/lib/mysql
--auth-root-authentication-method=normal
The option can also be set in an option file in an option
group supported by mysql_install_db. For example:
[mysql_install_db]
auth_root_authentication_method=normal
If the option is set in an option file and if
mysql_install_db is executed, then mysql_install_db will
read this option from the option file, and it will
automatically set this option.
Altering the User Account to Revert to the Previous
Authentication Method
If you have already installed MariaDB, and if the
root@localhost user account is already using unix_socket
authentication, then you can revert to the old
mysql_native_password authenticatio��<� Syntax
------
CREATE [OR REPLACE] USER [IF NOT EXISTS]
user_specification [,user_specification ...]
[REQUIRE {NONE | tls_option [[AND] tls_option ...] }]
[WITH resource_option [resource_option ...] ]
[password_option | lock_option]
user_specification:
username [authentication_option]
authentication_option:
IDENTIFIED BY 'password'
| IDENTIFIED BY PASSWORD 'password_hash'
| IDENTIFIED {VIA|WITH} authentication_rule [OR
authentication_rule ...]
authentication_rule:
authentication_plugin
| authentication_plugin {USING|AS}
'authentication_string'
| authentication_plugin {USING|AS} PASSWORD('password')
tls_option:
SSL
| X509
| CIPHER 'cipher'
| ISSUER 'issuer'
| SUBJECT 'subject'
resource_option:
MAX_QUERIES_PER_HOUR count
| MAX_UPDATES_PER_HOUR count
| MAX_CONNECTIONS_PER_HOUR count
| MAX_USER_CONNECTIONS count
| MAX_STATEMENT_TIME time
password_option:
PASSWORD EXPIRE
| PASSWORD EXPIRE DEFAULT
| PASSWORD EXPIRE NEVER
| PASSWORD EXPIRE INTERVAL N DAY
lock_option:
ACCOUNT LOCK
| ACCOUNT UNLOCK
}
Description
-----------
The CREATE USER statement creates new MariaDB accounts. To
use it, you must have the global CREATE USER privilege or
the INSERT privilege for the mysql database. For each
account, CREATE USER creates a new row in
the mysql.user table that has no privileges.
If any of the specified accounts, or any permissions for the
specified accounts, already exist, then the server returns
ERROR 1396 (HY000). If an error occurs, CREATE USER will
still create the accounts that do not result in an error.
Only one error is produced for all users which have not been
created:
ERROR 1396 (HY000):
Operation CREATE USER failed for 'u1'@'%','u2'@'%'
CREATE USER, DROP USER, CREATE ROLE, and DROP ROLE all
produce the
same error code when they fail.
See Account Names below for details on how account names are
specified.
OR REPLACE
If the optional OR REPLACE clause is used, it is basically a
shortcut for:
DROP USER IF EXISTS name;
CREATE USER name ...;
For example:
CREATE USER foo2@test IDENTIFIED BY 'password';
ERROR 1396 (HY000): Operation CREATE USER failed for
'foo2'@'test'
CREATE OR REPLACE USER foo2@test IDENTIFIED BY 'password';
Query OK, 0 rows affected (0.00 sec)
IF NOT EXISTS
When the IF NOT EXISTS clause is used, MariaDB will return a
warning instead of an error if the specified user already
exists.
For example:
CREATE USER foo2@test IDENTIFIED BY 'password';
ERROR 1396 (HY000): Operation CREATE USER failed for
'foo2'@'test'
CREATE USER IF NOT EXISTS foo2@test IDENTIFIED BY
'password';
Query OK, 0 rows affected, 1 warning (0.00 sec)
SHOW WARNINGS;
+-------+------+----------------------------------------------------+
| Level | Code | Message |
+-------+------+----------------------------------------------------+
| Note | 1973 | Can't create user 'foo2'@'test';
it already exists |
+-------+------+----------------------------------------------------+
1 row in set (0.00 sec
Authentication Options
IDENTIFIED BY 'password'
The optional IDENTIFIED BY clause can be used to provide an
account with a password. The password should be specified in
plain text. It will be hashed by the PASSWORD function prior
to being stored to the mysql.user table.
For example, if our password is mariadb, then we can create
the user with:
CREATE USER foo2@test IDENTIFIED BY 'mariadb';
If you do not specify a password with the IDENTIFIED BY
clause, the user
will be able to connect without a password. A blank password
is not a wildcard
to match any password. The user must connect without
providing a password if no
password is set.
The only authentication plugins that this clause supports
are mysql_native_password and mysql_old_password.
IDENTIFIED BY PASSWORD 'password_hash'
The optional IDENTIFIED BY PASSWORD clause can be used to
provide an account with a password that has already been
hashed. The password should be specified as a hash that was
provided by the PASSWORD function. It will be stored to the
mysql.user table as-is.
For example, if our password is mariadb, then we can find
the hash with:
SELECT PASSWORD('mariadb');
+-------------------------------------------+
| PASSWORD('mariadb') |
+-------------------------------------------+
| *54958E764CE10E50764C2EECBB71D01F08549980 |
+-------------------------------------------+
1 row in set (0.00 sec)
And then we can create a user with the hash:
CREATE USER foo2@test IDENTIFIED BY PASSWORD
'*54958E764CE10E50764C2EECBB71D01F08549980';
If you do not specify a password with the IDENTIFIED BY
clause, the user
will be able to connect without a password. A blank password
is not a wildcard
to match any password. The user must connect without
providing a password if no
password is set.
The only authentication plugins that this clause supports
are mysql_native_password and mysql_old_password.
IDENTIFIED {VIA|WITH} authentication_plugin
The optional IDENTIFIED VIA authentication_plugin allows you
to specify that the account should be authenticated by a
specific authentication plugin. The plugin name must be an
active authentication plugin as per SHOW PLUGINS. If it
doesn't show up in that output, then you will need to
install it with INSTALL PLUGIN or INSTALL SONAME.
For example, this could be used with the PAM authentication
plugin:
CREATE USER foo2@test IDENTIFIED VIA pam;
Some authentication plugins allow additional arguments to be
specified after a USING or AS keyword. For example, the PAM
authentication plugin accepts a service name:
CREATE USER foo2@test IDENTIFIED VIA pam USING 'mariadb';
The exact meaning of the additional argument would depend on
the specific authentication plugin.
The USING or AS keyword can also be used to provide a
plain-text password to a plugin if it's provided as an
argument to the PASSWORD() function. This is only valid for
authentication plugins that have implemented a hook for the
PASSWORD() function. For example, the ed25519 authentication
plugin supports this:
CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING
PASSWORD('secret');
One can specify many authentication plugins, they all works
as alternatives ways of authenticating a user:
CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING
PASSWORD('secret') OR unix_socket;
TLS Options
By default, MariaDB transmits data between the server and
clients without encrypting it. This is generally acceptable
when the server and client run on the same host or in
networks where security is guaranteed through other means.
However, in cases where the server and client exist on
separate networks or they are in a high-risk network, the
lack of encryption does introduce security concerns as a
malicious actor could potentially eavesdrop on the traffic
as it is sent over the network between them.
To mitigate this concern, MariaDB allows you to encrypt data
in transit between the server and clients using the
Transport Layer Security (TLS) protocol. TLS was formerly
known as Secure Socket Layer (SSL), but strictly speaking
the SSL protocol is a predecessor to TLS and, that version
of the protocol is now considered insecure. The
documentation still uses the term SSL often and for
compatibility reasons TLS-related server system and status
variables still use the prefix ssl_, but internally, MariaDB
only supports its secure successors.
See Secure Connections Overview for more information about
how to determine whether your MariaDB server has TLS
support.
You can set certain TLS-related restrictions for specific
user accounts. For instance, you might use this with user
accounts that require access to sensitive data while sending
it across networks that you do not control. These
restrictions can be enabled for a user account with the
CREATE USER, ALTER USER, or GRANT statements. The following
options are available:
Option | Description |
REQUIRE NONE | TLS is not required for this account, but can
still be used. |
REQUIRE SSL | The account must use TLS, but no valid X509
certificate is required. This option cannot be combined with
other TLS options. |
REQUIRE X509 | The account must use TLS andtX�W must have a
valid X509 certificate. This option implies REQUIRE SSL.
This option cannot be combined with other TLS options. |
REQUIRE ISSUER 'issuer' | The account must use TLS and
must have a valid X509 certificate. Also, the Certificate
Authority must be the one specified via the string issuer.
This option implies REQUIRE X509. This option can be
combined with the SUBJECT, and CIPHER options in any order.
|
REQUIRE SUBJECT 'subject' | The account must use TLS and
must have a valid X509 certificate. Also, the certificate's
Subject must be the one specified via the string subject.
This option implies REQUIRE X509. This option can be
combined with the ISSUER, and CIPHER options in any order. |
REQUIRE CIPHER 'cipher' | The account must use TLS, but no
valid X509 certificate is required. Also, the encryption
used for the connection must use one of the methods
specified in the string cipher. This option implies REQUIRE
SSL. This option can be combined with the ISSUER, and
SUBJECT options in any order. |
The REQUIRE keyword must be used only once for all specified
options, and the AND keyword can be used to separate
individual options, but it is not required.
For example, you can create a user account that requires
these TLS options with the following:
CREATE USER 'alice'@'%'
REQUIRE SUBJECT '/CN=alice/O=My Dom,
Inc./C=US/ST=Oregon/L=Portland'
AND ISSUER '/C=FI/ST=Somewhere/L=City/ O=Some
Company/CN=Peter Parker/emailAddress=p.parker@marvel.com'
AND CIPHER 'TLSv1.2';
If any of these options are set for a specific user account,
then any client who tries to connect with that user account
will have to be configured to connect with TLS.
See Securing Connections for Client and Server for
information on how to enable TLS on the client and server.
Resource Limit Options
MariaDB 10.2.0 introduced a number of resource limit
options.
It is possible to set per-account limits for certain server
resources. The following table shows the values that can be
set per account:
Limit Type | Decription |
MAX_QUERIES_PER_HOUR | Number of statements that the account
can issue per hour (including updates) |
MAX_UPDATES_PER_HOUR | Number of updates (not queries) that
the account can issue per hour |
MAX_CONNECTIONS_PER_HOUR | Number of connections that the
account can start per hour |
MAX_USER_CONNECTIONS | Number of simultaneous connections
that can be accepted from the same account; if it is 0,
max_connections will be used instead; if max_connections is
0, there is no limit for this account's simultaneous
connections. |
MAX_STATEMENT_TIME | Timeout, in seconds, for statements
executed by the user. See also Aborting Statements that
Exceed a Certain Time to Execute. |
If any of these limits are set to 0, then there is no limit
for that resource for that user.
Here is an example showing how to create a user with
resource limits:
CREATE USER 'someone'@'localhost' WITH
MAX_USER_CONNECTIONS 10
MAX_QUERIES_PER_HOUR 200;
The resources are tracked per account, which means
'user'@'server'; not per user name or per connection.
The count can be reset for all users using FLUSH
USER_RESOURCES, FLUSH PRIVILEGES or mysqladmin reload.
Per account resource limits are stored in the user table, in
the mysql database. Columns used for resources limits are
named max_questions, max_updates, max_connections (for
MAX_CONNECTIONS_PER_HOUR), and max_user_connections (for
MAX_USER_CONNECTIONS).
Account Names
Account names have both a user name component and a host
name component, and are specified as
'user_name'@'host_name'.
The user name and host name may be unquoted, quoted as
strings using double quotes (") or
single quotes ('), or quoted as identifiers using backticks
(`). You must use quotes
when using special characters (such as a hyphen) or wildcard
characters. If you quote, you
must quote the user name and host name separately (for
example 'user_name'@'host_name').
Host Name Component
If the host name is not provided, it is assumed to be '%'.
Host names may contain the wildcard characters % and _. They
are matched as if by
the LIKE clause. If you need to use a wildcard character
literally (for example, to
match a domain name with an underscore), prefix the
character with a backslash. See LIKE
for more information on escaping wildcard characters.
Host name matches are case-insensitive. Host names can match
either domain names or IP
addresses. Use 'localhost' as the host name to allow only
local client connections.
You can use a netmask to match a range of IP addresses using
'base_ip/netmask' as the
host name. A user with an IP address ip_addr will be allowed
to connect if the following
condition is true:
ip_addr & netmask = base_ip
You can only use netmasks that specify a multiple of 8 bits
of the address to match. That is,
only the following netmasks are allowed:
255.0.0.0
255.255.0.0
255.255.255.0
255.255.255.255
Using 255.255.255.255 is equivalent to not using a netmask
at all.
User Name Component
User names must match exactly, including case. A user name
that is empty is known as an anonymous account and is
allowed to match a login attempt with any user name
component. These are described more in the next section.
For valid identifiers to use as user names, see Identifier
Names.
It is possible for more than one account to match when a
user connects. MariaDB selects
the first matching account after sorting according to the
following criteria:
Accounts with an exact host name are sorted before accounts
using a wildcard in the
host name. Host names using a netmask are considered to be
exact for sorting.
Accounts with a wildcard in the host name are sorted
according to the position of
the first wildcard character. Those with a wildcard
character later in the host name
sort before those with a wildcard character earlier in the
host name.
Accounts with a non-empty user name sort before accounts
with an empty user name.
Accounts with an empty user name are sorted last. As
mentioned previously, these are known as anonymous accounts.
These are described more in the next section.
The following table shows a list of example account as
sorted by these criteria:
+---------+-------------+
| User | Host |
+---------+-------------+
| joffrey | 192.168.0.3 |
| | 192.168.0.% |
| joffrey | 192.168.% |
| | 192.168.% |
+---------+-------------+
Once connected, you only have the privileges granted to the
account that matched,
not all accounts that could have matched. For example,
consider the following
commands:
CREATE USER 'joffrey'@'192.168.0.3';
CREATE USER 'joffrey'@'%';
GRANT SELECT ON test.t1 to 'joffrey'@'192.168.0.3';
GRANT SELECT ON test.t2 to 'joffrey'@'%';
If you connect as joffrey from 192.168.0.3, you will have
the SELECT
privilege on the table test.t1, but not on the table
test.t2. If you connect as joffrey from any other IP
address, you will have the SELECT privilege on the table
test.t2, but not
on the table test.t1.
Beginning with MariaDB 5.5.31, usernames can be up to 80
characters long. From MariaDB 10.0 the system tables are all
by default this length. However, in order to enable this
feature in MariaDB 5.5, the following schema changes must be
made:
ALTER TABLE mysql.user MODIFY User CHAR(80) BINARY NOT NULL
DEFAULT '';
ALTER TABLE mysql.db MODIFY User CHAR(80) BINARY NOT NULL
DEFAULT '';
ALTER TABLE mysql.tables_priv MODIFY User CHAR(80) BINARY
NOT NULL DEFAULT '';
ALTER TABLE mysql.columns_priv MODIFY User CHAR(80) BINARY
NOT NULL DEFAULT '';
ALTER TABLE mysql.procs_priv MODIFY User CHAR(80) BINARY NOT
NULL DEFAULT '';
ALTER TABLE mysql.proc MODIFY definer CHAR(141) COLLATE
utf8_bin NOT NULL DEFAULT '';
ALTER TABLE mysql.event MODIFY definer CHAR(141) COLLATE
utf8_bin NOT NULL DEFAULT '';
ALTER TABLE mysql.proxies_priv MODIFY User CHAR(80) COLLATE
utf8_bin NOT NULL DEFAULT '';
ALTER TABLE mysql.proxies_priv MODIFY Proxied_user CHAR(80)
COLLATE utf8_bin NOT NULL DEFAULT '';
ALTER TABLE mysql.proxies_priv MODIFY Grantor CHAR(141)
COLLATE utf8_bin NOT NULL DEFAULT '';
ALTER TABLE mysql.servers MODIFY Username CHAR(80) NOT NULL
DEFAULT ''�| The ALTER USER statement was introduced in MariaDB 10.2.0.
Syntax
------
ALTER USER [IF EXISTS]
user_specification [,user_specification] ...
[REQUIRE {NONE | tls_option [[AND] tls_option] ...}]
[WITH resource_option [resource_option] ...]
[password_option | lock_option]
user_specification:
username [authentication_option]
authentication_option:
IDENTIFIED BY 'password'
| IDENTIFIED BY PASSWORD 'password_hash'
| IDENTIFIED {VIA|WITH} authentication_plugin
| IDENTIFIED {VIA|WITH} authentication_plugin {USING|AS}
'authentication_string'
| IDENTIFIED {VIA|WITH} authentication_plugin {USING|AS}
PASSWORD('password')
tls_option
SSL
| X509
| CIPHER 'cipher'
| ISSUER 'issuer'
| SUBJECT 'subject'
resource_option
MAX_QUERIES_PER_HOUR count
| MAX_UPDATES_PER_HOUR count
| MAX_CONNECTIONS_PER_HOUR count
| MAX_USER_CONNECTIONS count
| MAX_STATEMENT_TIME time
password_option:
PASSWORD EXPIRE
| PASSWORD EXPIRE DEFAULT
| PASSWORD EXPIRE NEVER
| PASSWORD EXPIRE INTERVAL N DAY
lock_option:
ACCOUNT LOCK
| ACCOUNT UNLOCK
}
Description
-----------
The ALTER USER statement modifies existing MariaDB accounts.
To use it, you must have the global CREATE USER privilege or
the UPDATE privilege for the mysql database. The global
SUPER privilege is also required if the read_only system
variable is enabled.
If any of the specified user accounts do not yet exist, an
error results. If an error occurs, ALTER USER will still
modify the accounts that do not result in an error. Only one
error is produced for all users which have not been
modified.
IF EXISTS
When the IF EXISTS clause is used, MariaDB will return a
warning instead of an error for each specified user that
does not exist.
Account Names
For ALTER USER statements, account names are specified as
the username argument in the same way as they are for CREATE
USER statements. See account names from the CREATE USER page
for details on how account names are specified.
CURRENT_USER or CURRENT_USER() can also be used to alter the
account logged into the current session. For example, to
change the current user's password to mariadb:
ALTER USER CURRENT_USER() IDENTIFIED BY 'mariadb';
Authentication Options
IDENTIFIED BY 'password'
The optional IDENTIFIED BY clause can be used to provide an
account with a password. The password should be specified in
plain text. It will be hashed by the PASSWORD function prior
to being stored to the mysql.user table.
For example, if our password is mariadb, then we can set the
account's password with:
ALTER USER foo2@test IDENTIFIED BY 'mariadb';
If you do not specify a password with the IDENTIFIED BY
clause, the user
will be able to connect without a password. A blank password
is not a wildcard
to match any password. The user must connect without
providing a password if no
password is set.
The only authentication plugins that this clause supports
are mysql_native_password and mysql_old_password.
IDENTIFIED BY PASSWORD 'password_hash'
The optional IDENTIFIED BY PASSWORD clause can be used to
provide an account with a password that has already been
hashed. The password should be specified as a hash that was
provided by the PASSWORD function. It will be stored to the
mysql.user table as-is.
For example, if our password is mariadb, then we can find
the hash with:
SELECT PASSWORD('mariadb');
+-------------------------------------------+
| PASSWORD('mariadb') |
+-------------------------------------------+
| *54958E764CE10E50764C2EECBB71D01F08549980 |
+-------------------------------------------+
1 row in set (0.00 sec)
And then we can set an account's password with the hash:
ALTER USER foo2@test IDENTIFIED BY PASSWORD
'*54958E764CE10E50764C2EECBB71D01F08549980';
If you do not specify a password with the IDENTIFIED BY
clause, the user
will be able to connect without a password. A blank password
is not a wildcard
to match any password. The user must connect without
providing a password if no
password is set.
The only authentication plugins that this clause supports
are mysql_native_password and mysql_old_password.
IDENTIFIED {VIA|WITH} authentication_plugin
The optional IDENTIFIED VIA authentication_plugin allows you
to specify that the account should be authenticated by a
specific authentication plugin. The plugin name must be an
active authentication plugin as per SHOW PLUGINS. If it
doesn't show up in that output, then you will need to
install it with INSTALL PLUGIN or INSTALL SONAME.
For example, this could be used with the PAM authentication
plugin:
ALTER USER foo2@test IDENTIFIED VIA pam;
Some authentication plugins allow additional arguments to be
specified after a USING or AS keyword. For example, the PAM
authentication plugin accepts a service name:
ALTER USER foo2@test IDENTIFIED VIA pam USING 'mariadb';
The exact meaning of the additional argument would depend on
the specific authentication plugin.
In MariaDB 10.4 and later, the USING or AS keyword can also
be used to provide a plain-text password to a plugin if
it's provided as an argument to the PASSWORD() function.
This is only valid for authentication plugins that have
implemented a hook for the PASSWORD() function. For example,
the ed25519 authentication plugin supports this:
ALTER USER safe@'%' IDENTIFIED VIA ed25519 USING
PASSWORD('secret');
TLS Options
By default, MariaDB transmits data between the server and
clients without encrypting it. This is generally acceptable
when the server and client run on the same host or in
networks where security is guaranteed through other means.
However, in cases where the server and client exist on
separate networks or they are in a high-risk network, the
lack of encryption does introduce security concerns as a
malicious actor could potentially eavesdrop on the traffic
as it is sent over the network between them.
To mitigate this concern, MariaDB allows you to encrypt data
in transit between the server and clients using the
Transport Layer Security (TLS) protocol. TLS was formerly
known as Secure Socket Layer (SSL), but strictly speaking
the SSL protocol is a predecessor to TLS and, that version
of the protocol is now considered insecure. The
documentation still uses the term SSL often and for
compatibility reasons TLS-related server system and status
variables still use the prefix ssl_, but internally, MariaDB
only supports its secure successors.
See Secure Connections Overview for more information about
how to determine whether your MariaDB server has TLS
support.
You can set certain TLS-related restrictions for specific
user accounts. For instance, you might use this with user
accounts that require access to sensitive data while sending
it across networks that you do not control. These
restrictions can be enabled for a user account with the
CREATE USER, ALTER USER, or GRANT statements. The following
options are available:
Option | Description |
REQUIRE NONE | TLS is not required for this account, but can
still be used. |
REQUIRE SSL | The account must use TLS, but no valid X509
certificate is required. This option cannot be combined with
other TLS options. |
REQUIRE X509 | The account must use TLS and must have a
valid X509 certificate. This option implies REQUIRE SSL.
This option cannot be combined with other TLS options. |
REQUIRE ISSUER 'issuer' | The account must use TLS and
must have a valid X509 certificate. Also, the Certificate
Authority must be the one specified via the string issuer.
This option implies REQUIRE X509. This option can be
combined with the SUBJECT, and CIPHER options in any order.
|
REQUIRE SUBJECT 'subject' | The account must use TLS and
must have a valid X509 certificate. Also, the certificate's
Subject must be the one specified via the string subject.
This option implies REQUIRE X509. This option can be
combined with the ISSUER, and CIPHER options in any order. |
REQUIRE CIPHER 'cipher' | The account must use TLS, but no
valid X509 certificate is required. Also, the encryption
used for the connection must use one of the methods
specified in the string cipher. This option implies REQUIRE
SSL. This option can be combiK��a �
�ined with the ISSUER, and
SUBJECT options in any order. |
The REQUIRE keyword must be used only once for all specified
options, and the AND keyword can be used to separate
individual options, but it is not required.
For example, you can alter a user account to require these
TLS options with the following:
ALTER USER 'alice'@'%'
REQUIRE SUBJECT '/CN=alice/O=My Dom,
Inc./C=US/ST=Oregon/L=Portland'
AND ISSUER '/C=FI/ST=Somewhere/L=City/ O=Some
Company/CN=Peter Parker/emailAddress=p.parker@marvel.com'
AND CIPHER 'TLSv1.2';
If any of these options are set for a specific user account,
then any client who tries to connect with that user account
will have to be configured to connect with TLS.
See Securing Connections for Client and Server for
information on how to enable TLS on the client and server.
Resource Limit Options
MariaDB 10.2.0 introduced a number of resource limit
options.
It is possible to set per-account limits for certain server
resources. The following table shows the values that can be
set per account:
Limit Type | Decription |
MAX_QUERIES_PER_HOUR | Number of statements that the account
can issue per hour (including updates) |
MAX_UPDATES_PER_HOUR | Number of updates (not queries) that
the account can issue per hour |
MAX_CONNECTIONS_PER_HOUR | Number of connections that the
account can start per hour |
MAX_USER_CONNECTIONS | Number of simultaneous connections
that can be accepted from the same account; if it is 0,
max_connections will be used instead; if max_connections is
0, there is no limit for this account's simultaneous
connections. |
MAX_STATEMENT_TIME | Timeout, in seconds, for statements
executed by the user. See also Aborting Statements that
Exceed a Certain Time to Execute. |
If any of these limits are set to 0, then there is no limit
for that resource for that user.
Here is an example showing how to set an account's resource
limits:
ALTER USER 'someone'@'localhost' WITH
MAX_USER_CONNECTIONS 10
MAX_QUERIES_PER_HOUR 200;
The resources are tracked per account, which means
'user'@'server'; not per user name or per connection.
The count can be reset for all users using FLUSH
USER_RESOURCES, FLUSH PRIVILEGES or mysqladmin reload.
Per account resource limits are stored in the user table, in
the mysql database. Columns used for resources limits are
named max_questions, max_updates, max_connections (for
MAX_CONNECTIONS_PER_HOUR), and max_user_connections (for
MAX_USER_CONNECTIONS).
Password Expiry
Besides automatic password expiry, as determined by
default_password_lifetime, password expiry times can be set
on an individual user basis, overriding the global setting,
for example:
ALTER USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL
120 DAY;
ALTER USER 'monty'@'localhost' PASSWORD EXPIRE NEVER;
ALTER USER 'monty'@'localhost' PASSWORD EXPIRE DEFAULT;
See User Password Expiry for more details.
Account Locking
Account locking permits privileged administrators to
lock/unlock user accounts. No new client connections will be
permitted if an account is locked (existing connections are
not affected). For example:
ALTER USER 'marijn'@'localhost' ACCOUNT LOCK;
See Account Locking for more details.
URL: https://mariadb.com/kb/en/alter-user/https://mariadb.com/kb/en/flush/https://mariadb.com/kb/en/show-status/https://mariadb.com/kb/en/explain/https://mariadb.com/kb/en/alter-table/https://mariadb.com/kb/en/create-function/https://mariadb.com/kb/en/create-procedure/https://mariadb.com/kb/en/create-table/https://mariadb.com/kb/en/create-view/AL);
INSERT INTO table2 (a) VALUES (1);
SELECT * FROM table2;
+------+------------+
| a | b |
+------+------------+
| 1 | 0000000002 |
+------+------------+
1 row in set (0.00 sec)
You can also use virtual columns to implement a "poor
man's partial index". See example at the end of Unique
Index.
URL: https://mariadb.com/kb/en/generated-columns/ d�
& �
' �
+ e
* ?
&
" � & � � ��E �g x ~$
DROP USERSyntax
------
DROP USER [IF EXISTS] user_name [, user_name] ...
Description
-----------
The DROP USER statement removes one or more MariaDB
accounts. It removes
privilege rows for the account from all grant tables. To use
this statement,
you must have the global CREATE USER privilege
or the DELETE privilege for the mysql database.
Each account is named using the same format as for the
CREATE USER
statement; for example, 'jeffrey'@'localhost'. If you
specify
only the user name part of the account name, a host name
part of '%' is
used. For additional information about specifying account
names, see
CREATE USER.
Note that, if you specify an account that is currently
connected, it will not
be deleted until the connection is closed. The connection
will not be
automatically closed.
If any of the specified user accounts do not exist, ERROR
1396 (HY000)
results. If an error occurs, DROP USER will still drop the
accounts that do
not result in an error. Only one error is produced for all
users which have not
been dropped:
ERROR 1396 (HY000): Operation DROP USER failed for
'u1'@'%','u2'@'%'
Failed CREATE or DROP operations, for both users and roles,
produce the
same error code.
IF EXISTS
The IF EXISTS clause was added in MariaDB 10.1.3
If the IF EXISTS clause is used, MariaDB will return a note
instead of an error if the user does not exist.
Examples
--------
DROP USER bob;
IF EXISTS:
DROP USER bob;
ERROR 1396 (HY000): Operation DROP USER failed for
'bob'@'%'
DROP USER IF EXISTS bob;
Query OK, 0 rows affected, 1 warning (0.00 sec)
SHOW WARNINGS;
+-------+------+---------------------------------------------+
| Level | Code | Message |
+-------+------+---------------------------------------------+
| Note | 1974 | Can't drop user 'bob'@'%'; it doesn't
exist |
+-------+------+---------------------------------------------+
URL: https://mariadb.com/kb/en/drop-user/https://mariadb.com/kb/en/drop-user/ z H /
User Password ExpiryUser password expiry was introduced in MariaDB 10.4.3.
Password expiry permits administrators to expire user
passwords, either manually or automatically.
System Variables
There are two system variables which affect password expiry:
default_password_lifetime, which determines the amount of
time between requiring the user to change their password. 0,
the default, means automatic password expiry is not active.
The second variable, disconnect_on_expired_password
determines whether a client is permitted to connect if their
password has expired, or whether they are permitted to
connect in sandbox mode, able to perform a limited subset of
queries related to resetting the password, in particular SET
PASSWORD and SET.
Setting a Password Expiry Limit for a User
Besides automatic password expiry, as determined by
default_password_lifetime, password expiry times can be set
on an individual user basis, overriding the global using the
CREATE USER or ALTER USER statements, for example:
CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL
120 DAY;
ALTER USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL
120 DAY;
Limits can be disabled by use of the NEVER keyword, for
example:
CREATE USER 'monty'@'localhost' PASSWORD EXPIRE NEVER;
ALTER USER 'monty'@'localhost' PASSWORD EXPIRE NEVER;
A manually set limit can be restored the system default by
use of DEFAULT, for example:
CREATE USER 'monty'@'localhost' PASSWORD EXPIRE DEFAULT;
ALTER USER 'monty'@'localhost' PASSWORD EXPIRE DEFAULT;
SHOW CREATE USER
The SHOW CREATE USER statement will display information
about the password expiry status of the user. Unlike MySQL,
it will not display if the user is unlocked, or if the
password expiry is set to default.
CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL
120 DAY;
CREATE USER 'konstantin'@'localhost' PASSWORD EXPIRE
NEVER;
CREATE USER 'amse'@'localhost' PASSWORD EXPIRE DEFAULT;
SHOW CREATE USER 'monty'@'localhost';
+------------------------------------------------------------------+
| CREATE USER for monty@localhost |
+------------------------------------------------------------------+
| CREATE USER 'monty'@'localhost' PASSWORD EXPIRE
INTERVAL 120 DAY |
+------------------------------------------------------------------+
SHOW CREATE USER 'konstantin'@'localhost';
+------------------------------------------------------------+
| CREATE USER for konstantin@localhost |
+------------------------------------------------------------+
| CREATE USER 'konstantin'@'localhost' PASSWORD EXPIRE
NEVER |
+------------------------------------------------------------+
SHOW CREATE USER 'amse'@'localhost';
+--------------------------------+
| CREATE USER for amse@localhost |
+--------------------------------+
| CREATE USER 'amse'@'localhost' |
+--------------------------------+
--connect-expired-password Client Option
The mysql client --connect-expired-password option notifies
the server that the client is prepared to handle expired
password sandbox mode (even if the --batch option was
specified).
URL: https://mariadb.com/kb/en/user-password-expiry/https://mariadb.com/kb/en/user-password-expiry/ � � !Syntax
------
NOT, !
Description
-----------
Logical NOT. Evaluates to 1 if the operand is 0, to 0 if the
operand
is non-zero, and NOT NULL returns NULL.
By default, the ! operator has a higher precedence. If the
HIGH_NOT_PRECEDENCE SQL_MODE flag is set, NOT and ! have the
same precedence.
Examples
--------
SELECT NOT 10;
+--------+
| NOT 10 |
+--------+
| 0 |
+--------+
SELECT NOT 0;
+-------+
| NOT 0 |
+-------+
| 1 |
+-------+
SELECT NOT NULL;
+----------+
| NOT NULL |
+----------+
| NULL |
+----------+
SELECT ! (1+1);
+---------+
| ! (1+1) |
+---------+
| 0 |
+---------+
SELECT ! 1+1;
+-------+
| ! 1+1 |
+-------+
| 1 |
+-------+
URL: https://mariadb.com/kb/en/not/https://mariadb.com/kb/en/not/ �
� &&Syntax
------
AND, &&
Description
-----------
Logical AND. Evaluates to 1 if all operands are non-zero and
not NULL,
to 0 if one or more operands are 0, otherwise NULL is
returned.
For this operator, short-circuit evaluation can be used.
Examples
--------
SELECT 1 && 1;
+--------+
| 1 && 1 |
+--------+
| 1 |
+--------+
SELECT 1 && 0;
+--------+
| 1 && 0 |
+--------+
| 0 |
+--------+
SELECT 1 && NULL;
+-----------+
| 1 && NULL |
+-----------+
| NULL |
+-----------+
SELECT 0 && NULL;
+-----------+
| 0 && NULL |
+-----------+
| 0 |
+-----------+
SELECT NULL && 0;
+-----------+
| NULL && 0 |
+-----------+
| 0 |
+-----------+
URL: https://mariadb.com/kb/en/and/https://mariadb.com/kb/en/and/ � � XORSyntax
------
XOR
Description
-----------
XOR stands for eXclusive OR. Returns NULL if either operand
is NULL. For non-NULL
operands, evaluates to 1 if an odd number of operands is
non-zero,
otherwise 0 is returned.
Examples
--------
SELECT 1 XOR 1;
+---------+
| 1 XOR 1 |
+---------+
| 0 |
+---------+
SELECT 1 XOR 0;
+---------+
| 1 XOR 0 |
+---------+
| 1 |
+---------+
SELECT 1 XOR NULL;
+------------+
| 1 XOR NULL |
+------------+
| NULL |
+------------+
In the following example, the right 1 XOR 1 is evaluated
first, and returns 0. Then, 1 XOR 0 is evaluated, and 1 is
returned.
SELECT 1 XOR 1 XOR 1;
+---------------+
| 1 XOR 1 XOR 1 |
+---------------+
| 1 |
+---------------+
URL: https://mariadb.com/kb/en/xor/https://mariadb.com/kb/en/xor/ V+[�^��� ���;[ Syntax
------
GRANT
priv_type [(column_list)]
[, priv_type [(column_list)]] ...
ON [object_type] priv_level
TO user_specification [ user_options ...]
user_specification:
username [authentication_option]
authentication_option:
IDENTIFIED BY 'password'
| IDENTIFIED BY PASSWORD 'password_hash'
| IDENTIFIED {VIA|WITH} authentication_rule [OR
authentication_rule ...]
authentication_rule:
authentication_plugin
| authentication_plugin {USING|AS}
'authentication_string'
| authentication_plugin {USING|AS} PASSWORD('password')
GRANT PROXY ON username
TO username [, username] ...
[WITH GRANT OPTION]
user_options:
[REQUIRE {NONE | tls_option [[AND] tls_option] ...}]
[WITH with_option [with_option] ...]
object_type:
TABLE
| FUNCTION
| PROCEDURE
priv_level:
*
| *.*
| db_name.*
| db_name.tbl_name
| tbl_name
| db_name.routine_name
with_option:
GRANT OPTION
| resource_option
resource_option:
MAX_QUERIES_PER_HOUR count
| MAX_UPDATES_PER_HOUR count
| MAX_CONNECTIONS_PER_HOUR count
| MAX_USER_CONNECTIONS count
| MAX_STATEMENT_TIME time
tls_option:
SSL
| X509
| CIPHER 'cipher'
| ISSUER 'issuer'
| SUBJECT 'subject'
Description
-----------
The GRANT statement allows you to grant privileges or roles
to accounts. To use GRANT, you must have the GRANT OPTION
privilege, and you must have the privileges that you are
granting.
Use the REVOKE statement to revoke privileges granted with
the GRANT statement.
Use the SHOW GRANTS statement to determine what privileges
an account has.
Account Names
For GRANT statements, account names are specified as the
username argument in the same way as they are for CREATE
USER statements. See account names from the CREATE USER page
for details on how account names are specified.
Implicit Account Creation
The GRANT statement also allows you to implicitly create
accounts in some cases.
If the account does not yet exist, then GRANT can implicitly
create it. To implicitly create an account with GRANT, a
user is required to have the same privileges that would be
required to explicitly create the account with the CREATE
USER statement.
If the NO_AUTO_CREATE_USER SQL_MODE is set, then accounts
can only be created if authentication information is
specified, or with a CREATE USER statement. If no
authentication information is provided, GRANT will produce
an error when the specified account does not exist, for
example:
show variables like '%sql_mode%' ;
+---------------+--------------------------------------------+
| Variable_name | Value |
+---------------+--------------------------------------------+
| sql_mode | NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |
+---------------+--------------------------------------------+
GRANT USAGE ON *.* TO 'user123'@'%' IDENTIFIED BY '';
ERROR 1133 (28000): Can't find any matching row in the user
table
GRANT USAGE ON *.* TO 'user123'@'%' IDENTIFIED VIA PAM
using 'mariadb' require ssl ;
Query OK, 0 rows affected (0.00 sec)
select host, user from mysql.user where user='user123' ;
+------+----------+
| host | user |
+------+----------+
| % | user123 |
+------+----------+
Privilege Levels
Privileges can be set globally, for an entire database, for
a table or routine,
or for individual columns in a table. Certain privileges can
only be set at
certain levels.
Global privileges are granted using *.* for
priv_level. Global privileges include privileges to
administer the database
and manage user accounts, as well as privileges for all
tables, functions, and
procedures. Global privileges are stored in the mysql.user
table.
Database privileges are granted using db_name.*
for priv_level, or using just * to use default database.
Database
privileges include privileges to create tables and
functions, as well as
privileges for all tables, functions, and procedures in the
database. Database privileges are stored in the mysql.db
table.
Table privileges are granted using db_name.tbl_name
for priv_level, or using just tbl_name to specify a table in
the default
database. The TABLE keyword is optional. Table privileges
include the
ability to select and change data in the table. Certain
table privileges can
be granted for individual columns.
Column privileges are granted by specifying a table for
priv_level and providing a column list after the privilege
type. They allow
you to control exactly which columns in a table users can
select and change.
Function privileges are granted using FUNCTION
db_name.routine_name
for priv_level, or using just FUNCTION routine_name to
specify a function
in the default database.
Procedure privileges are granted using PROCEDURE
db_name.routine_name
for priv_level, or using just PROCEDURE routine_name to
specify a procedure
in the default database.
The USAGE Privilege
The USAGE privilege grants no real privileges. The SHOW
GRANTS
statement will show a global USAGE privilege for a
newly-created user. You
can use USAGE with the GRANT statement to change options
like GRANT OPTION
and MAX_USER_CONNECTIONS without changing any account
privileges.
The ALL PRIVILEGES Privilege
The ALL PRIVILEGES privilege grants all available
privileges. Granting all
privileges only affects the given privilege level. For
example, granting all
privileges on a table does not grant any privileges on the
database or globally.
Using ALL PRIVILEGES does not grant the special GRANT OPTION
privilege.
You can use ALL instead of ALL PRIVILEGES.
The GRANT OPTION Privilege
Use the WITH GRANT OPTION clause to give users the ability
to grant privileges
to other users at the given privilege level. Users with the
GRANT OPTION privilege can
only grant privileges they have. They cannot grant
privileges at a higher privilege level than
they have the GRANT OPTION privilege.
The GRANT OPTION privilege cannot be set for individual
columns.
If you use WITH GRANT OPTION when specifying column
privileges,
the GRANT OPTION privilege will be granted for the entire
table.
Using the WITH GRANT OPTION clause is equivalent to listing
GRANT OPTION
as a privilege.
Global Privileges
The following table lists the privileges that can be granted
globally. You can
also grant all database, table, and function privileges
globally. When granted
globally, these privileges apply to all databases, tables,
or functions,
including those created later.
To set a global privilege, use *.* for priv_level.
Privilege | Description |
CREATE USER | Create a user using the CREATE USER statement,
or implicitly create a user with the GRANT statement. |
FILE | Read and write files on the server, using statements
like LOAD DATA INFILE or functions like LOAD_FILE(). Also
needed to create CONNECT outward tables. MariaDB server must
have the permissions to access those files. |
GRANT OPTION | Grant global privileges. You can only grant
privileges that you have. |
PROCESS | Show information about the active processes, via
SHOW PROCESSLIST or mysqladmin processlist. |
RELOAD | Execute FLUSH statements or equivalent mysqladmin
commands. |
REPLICATION CLIENT | Execute SHOW MASTER STATUS and SHOW
SLAVE STATUS informative statements. |
REPLICATION SLAVE | Accounts used by slave servers on the
master need this privilege. This is needed to get the
updates made on the master. |
SHOW DATABASES | List all databases using the SHOW DATABASES
statement. Without the SHOW DATABASES privilege, you can
still issue the SHOW DATABASES statement, but it will only
list databases containing tables on which you have
privileges. |
SHUTDOWN | Shut down the server using SHUTDOWN or the
mysqladmin shutdown command. |
SUPER | Execute superuser statements: CHANGE MASTER TO, KILL
(users who do not have this privilege can only KILL their
own threads), PURGE LOGS, SET global system variables, or
the mysqladmin debug command. Also, this permission allows
the user to write data even if the read_only startup option
is set, enable or disable logging, enable or disable
replication on slaves, specify a DEFINER for statements that
support that clause, connect once after reaching the
MAX_CONNECTIONS. If a statement has been specified for the
init-connect mysqld opt�r�M ion, that command will not be
executed when a user with SUPER privileges connects to the
server. |
Database Privileges
The following table lists the privileges that can be granted
at the database
level. You can also grant all table and function privileges
at the database
level. Table and function privileges on a database apply to
all tables or
functions in that database, including those created later.
To set a privilege for a database, specify the database
using
db_name.* for priv_level, or just use *
to specify the default database.
Privilege | Description |
CREATE | Create a database using the CREATE DATABASE
statement, when the privilege is granted for a database. You
can grant the CREATE privilege on databases that do not yet
exist. This also grants the CREATE privilege on all tables
in the database. |
CREATE ROUTINE | Create Stored Programs using the CREATE
PROCEDURE and CREATE FUNCTION statements. |
CREATE TEMPORARY TABLES | Create temporary tables with the
CREATE TEMPORARY TABLE statement. This privilege enable
writing and dropping those temporary tables |
DROP | Drop a database using the DROP DATABASE statement,
when the privilege is granted for a database. This also
grants the DROP privilege on all tables in the database. |
EVENT | Create, drop and alter EVENTs. Added in MySQL 5.1.6.
|
GRANT OPTION | Grant database privileges. You can only grant
privileges that you have. |
LOCK TABLES | Acquire explicit locks using the LOCK TABLES
statement; you also need to have the SELECT privilege on a
table, in order to lock it. |
Table Privileges
Privilege | Description |
ALTER | Change the structure of an existing table using the
ALTER TABLE statement. |
CREATE | Create a table using the CREATE TABLE statement.
You can grant the CREATE privilege on tables that do not yet
exist. |
CREATE VIEW | Create a view using the CREATE_VIEW statement.
|
DELETE | Remove rows from a table using the DELETE
statement. |
DELETE HISTORY | Remove historical rows from a table using
the DELETE HISTORY statement. Displays as DELETE VERSIONING
ROWS when running SHOW GRANTS until MariaDB 10.3.15 and
until MariaDB 10.4.5 (MDEV-17655), or when running SHOW
PRIVILEGES (MDEV-20382). From MariaDB 10.3.4. From MariaDB
10.3.5, if a user has the SUPER privilege but not this
privilege, running mysql_upgrade will grant this privilege
as well. |
DROP | Drop a table using the DROP TABLE statement or a view
using the DROP VIEW statement. Also required to execute the
TRUNCATE TABLE statement. |
GRANT OPTION | Grant table privileges. You can only grant
privileges that you have. |
INDEX | Create an index on a table using the CREATE INDEX
statement. Without the INDEX privilege, you can still create
indexes when creating a table using the CREATE TABLE
statement if the you have the CREATE privilege, and you can
create indexes using the ALTER TABLE statement if you have
the ALTER privilege. |
INSERT | Add rows to a table using the INSERT statement. The
INSERT privilege can also be set on individual columns; see
Column Privileges below for details. |
REFERENCES | Unused. |
SELECT | Read data from a table using the SELECT statement.
The SELECT privilege can also be set on individual columns;
see Column Privileges below for details. |
SHOW VIEW | Show the CREATE VIEW statement to create a view
using the SHOW CREATE VIEW statement. |
TRIGGER | Execute triggers associated to tables you update,
execute the CREATE TRIGGER and DROP TRIGGER statements. You
will still be able to see triggers. |
UPDATE | Update existing rows in a table using the UPDATE
statement. UPDATE statements usually include a WHERE clause
to update only certain rows. You must have SELECT privileges
on the table or the appropriate columns for the WHERE
clause. The UPDATE privilege can also be set on individual
columns; see Column Privileges below for details. |
Column Privileges
Some table privileges can be set for individual columns of a
table. To use
column privileges, specify the table explicitly and provide
a list of column
names after the privilege type. For example, the following
statement would allow
the user to read the names and positions of employees, but
not other information
from the same table, such as salaries.
GRANT SELECT (name, position) on Employee to
'jeffrey'@'localhost';
Privilege | Description |
INSERT (column_list) | Add rows specifying values in columns
using the INSERT statement. If you only have column-level
INSERT privileges, you must specify the columns you are
setting in the INSERT statement. All other columns will be
set to their default values, or NULL. |
REFERENCES (column_list) | Unused. |
SELECT (column_list) | Read values in columns using the
SELECT statement. You cannot access or query any columns for
which you do not have SELECT privileges, including in WHERE,
ON, GROUP BY, and ORDER BY clauses. |
UPDATE (column_list) | Update values in columns of existing
rows using the UPDATE statement. UPDATE statements usually
include a WHERE clause to update only certain rows. You must
have SELECT privileges on the table or the appropriate
columns for the WHERE clause. |
Function Privileges
Privilege | Description |
ALTER ROUTINE | Change the characteristics of a stored
function using the ALTER FUNCTION statement. |
EXECUTE | Use a stored function. You need SELECT privileges
for any tables or columns accessed by the function. |
GRANT OPTION | Grant function privileges. You can only grant
privileges that you have. |
Procedure Privileges
Privilege | Description |
ALTER ROUTINE | Change the characteristics of a stored
procedure using the ALTER PROCEDURE statement. |
EXECUTE | Execute a stored procedure using the CALL
statement. The privilege to call a procedure may allow you
to perform actions you wouldn't otherwise be able to do,
such as insert rows into a table. |
GRANT OPTION | Grant procedure privileges. You can only
grant privileges that you have. |
Proxy Privileges
Privilege | Description |
PROXY | Permits one user to be a proxy for another. |
The PROXY privilege allows one user to proxy as another
user, which means their privileges change to that of the
proxy user, and the CURRENT_USER() function returns the user
name of the proxy user.
The PROXY privilege only works with authentication plugins
that support it. The default mysql_native_password
authentication plugin does not support proxy users.
The pam authentication plugin is the only plugin included
with MariaDB that currently supports proxy users. The PROXY
privilege is commonly used with the pam authentication
plugin to enable user and group mapping with PAM.
For example, to grant the PROXY privilege to an anonymous
account that authenticates with the pam authentication
plugin, you could execute the following:
CREATE USER 'dba'@'%' IDENTIFIED BY 'strongpassword';
GRANT ALL PRIVILEGES ON *.* TO 'dba'@'%' ;
CREATE USER ''@'%' IDENTIFIED VIA pam USING 'mariadb';
GRANT PROXY ON 'dba'@'%' TO ''@'%';
A user account can only grant the PROXY privilege for a
specific user account if the granter also has the PROXY
privilege for that specific user account, and if that
privilege is defined WITH GRANT OPTION. For example, the
following example fails because the granter does not have
the PROXY privilege for that specific user account at all:
SELECT USER(), CURRENT_USER();
+-----------------+-----------------+
| USER() | CURRENT_USER() |
+-----------------+-----------------+
| alice@localhost | alice@localhost |
+-----------------+-----------------+
SHOW GRANTS;
+-----------------------------------------------------------------------------------------------------------------------+
| Grants for alice@localhost |
+-----------------------------------------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost'
IDENTIFIED BY PASSWORD
'*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' |
+-----------------------------------------------------------------------------------------------------------------------+
GRANT PROXY�٢[ ON 'dba'@'localhost' TO
'bob'@'localhost';
ERROR 1698 (28000): Access denied for user
'alice'@'localhost'
And the following example fails because the granter does
have the PROXY privilege for that specific user account, but
it is not defined WITH GRANT OPTION:
SELECT USER(), CURRENT_USER();
+-----------------+-----------------+
| USER() | CURRENT_USER() |
+-----------------+-----------------+
| alice@localhost | alice@localhost |
+-----------------+-----------------+
SHOW GRANTS;
+-----------------------------------------------------------------------------------------------------------------------+
| Grants for alice@localhost |
+-----------------------------------------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost'
IDENTIFIED BY PASSWORD
'*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' |
| GRANT PROXY ON 'dba'@'localhost' TO
'alice'@'localhost' |
+-----------------------------------------------------------------------------------------------------------------------+
MariaDB [(none)]> GRANT PROXY ON 'dba'@'localhost' TO
'bob'@'localhost';
ERROR 1698 (28000): Access denied for user
'alice'@'localhost'
But the following example succeeds because the granter does
have the PROXY privilege for that specific user account, and
it is defined WITH GRANT OPTION:
SELECT USER(), CURRENT_USER();
+-----------------+-----------------+
| USER() | CURRENT_USER() |
+-----------------+-----------------+
| alice@localhost | alice@localhost |
+-----------------+-----------------+
SHOW GRANTS;
+-----------------------------------------------------------------------------------------------------------------------------------------+
| Grants for alice@localhost |
+-----------------------------------------------------------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost'
IDENTIFIED BY PASSWORD
'*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' WITH GRANT
OPTION |
| GRANT PROXY ON 'dba'@'localhost' TO
'alice'@'localhost' WITH GRANT OPTION |
+-----------------------------------------------------------------------------------------------------------------------------------------+
GRANT PROXY ON 'dba'@'localhost' TO
'bob'@'localhost';
Query OK, 0 rows affected (0.004 sec)
A user account can grant the PROXY privilege for any other
user account if the granter has the PROXY privilege for the
''@'%' anonymous user account, like this:
GRANT PROXY ON ''@'%' TO 'dba'@'localhost' WITH
GRANT OPTION;
For example, the following example succeeds because the user
can grant the PROXY privilege for any other user account:
SELECT USER(), CURRENT_USER();
+-----------------+-----------------+
| USER() | CURRENT_USER() |
+-----------------+-----------------+
| alice@localhost | alice@localhost |
+-----------------+-----------------+
SHOW GRANTS;
+-----------------------------------------------------------------------------------------------------------------------------------------+
| Grants for alice@localhost |
+-----------------------------------------------------------------------------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'alice'@'localhost'
IDENTIFIED BY PASSWORD
'*2470C0C06DEE42FD1618BB99005ADCA2EC9D1E19' WITH GRANT
OPTION |
| GRANT PROXY ON ''@'%' TO 'alice'@'localhost' WITH
GRANT OPTION |
+-----------------------------------------------------------------------------------------------------------------------------------------+
GRANT PROXY ON 'app1_dba'@'localhost' TO
'bob'@'localhost';
Query OK, 0 rows affected (0.004 sec)
GRANT PROXY ON 'app2_dba'@'localhost' TO
'carol'@'localhost';
Query OK, 0 rows affected (0.004 sec)
The default root user accounts created by mysql_install_db
have this privilege. For example:
GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH
GRANT OPTION;
GRANT PROXY ON ''@'%' TO 'root'@'localhost' WITH
GRANT OPTION;
This allows the default root user accounts to grant the
PROXY privilege for any other user account, and it also
allows the default root user accounts to grant others the
privilege to do the same.
Authentication Options
The authentication options for the GRANT statement are the
same as those for the CREATE USER statement.
IDENTIFIED BY 'password'
The optional IDENTIFIED BY clause can be used to provide an
account with a password. The password should be specified in
plain text. It will be hashed by the PASSWORD function prior
to being stored to the mysql.user table.
For example, if our password is mariadb, then we can create
the user with:
GRANT USAGE ON *.* TO foo2@test IDENTIFIED BY 'mariadb';
If you do not specify a password with the IDENTIFIED BY
clause, the user
will be able to connect without a password. A blank password
is not a wildcard
to match any password. The user must connect without
providing a password if no
password is set.
If the user account already exists and if you provide the
IDENTIFIED BY clause, then the user's password will be
changed. You must have the privileges needed for the SET
PASSWORD
statement to change a user's password with GRANT.
The only authentication plugins that this clause supports
are mysql_native_password and mysql_old_password.
IDENTIFIED BY PASSWORD 'password_hash'
The optional IDENTIFIED BY PASSWORD clause can be used to
provide an account with a password that has already been
hashed. The password should be specified as a hash that was
provided by the PASSWORD function. It will be stored to the
mysql.user table as-is.
For example, if our password is mariadb, then we can find
the hash with:
SELECT PASSWORD('mariadb');
+-------------------------------------------+
| PASSWORD('mariadb') |
+-------------------------------------------+
| *54958E764CE10E50764C2EECBB71D01F08549980 |
+-------------------------------------------+
1 row in set (0.00 sec)
And then we can create a user with the hash:
GRANT USAGE ON *.* TO foo2@test IDENTIFIED BY PASSWORD
'*54958E764CE10E50764C2EECBB71D01F08549980';
If you do not specify a password with the IDENTIFIED BY
clause, the user
will be able to connect without a password. A blank password
is not a wildcard
to match any password. The user must connect without
providing a password if no
password is set.
If the user account already exists and if you provide the
IDENTIFIED BY clause, then the user's password will be
changed. You must have the privileges needed for the SET
PASSWORD
statement to change a user's password with GRANT.
The only authentication plugins that this clause supports
are mysql_native_password and mysql_old_password.
IDENTIFIED {VIA|WITH} authentication_plugin
The optional IDENTIFIED VIA authentication_plugin allows you
to specify that the account should be authenticated by a
specific authentication plugin. The plugin name must be an
active authentication plugin as per SHOW PLUGINS. If it
doesn't show up in that output, then you will need to
install it with INSTALL PLUGIN or INSTALL SONAME.
For example, this could be used with the PAM authentication
plugin:
GRANT USAGE ON *.* TO foo2@test IDENTIFIED VIA pam;
Some authentication plugins allow additional arguments to be
specified after a USING or AS keyword. For example, the PAM
authentication plugin accepts a service name:
GRANT USAGE ON *.* TO foo2@test IDENTIFIED VIA pam USING
'mariadb';
The exact meaning of the additional argument would depend on
the specific authentication plugin.
The USING or AS keyword can also be used to provide a
plain-text password to a plugin if it's provided as an
argument to the PASSWORD() function. This is only valid for
authentication plugins that have implemented a hook for the
PASSWORD() function. For example, the ed25519 authentication
plugin supports this:
CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING
PASSWORD('secret');
One can specify many authentication plugins, they all works
as alternatives ways of authenticating a user:
CREATE USER safe@'%' IDENTIFIED VIA ed25519 USING
PASSWORD('secret') OR unix_socket;
Resource Limit OptioO�J� ns
MariaDB 10.2.0 introduced a number of resource limit
options.
It is possible to set per-account limits for certain server
resources. The following table shows the values that can be
set per account:
Limit Type | Decription |
MAX_QUERIES_PER_HOUR | Number of statements that the account
can issue per hour (including updates) |
MAX_UPDATES_PER_HOUR | Number of updates (not queries) that
the account can issue per hour |
MAX_CONNECTIONS_PER_HOUR | Number of connections that the
account can start per hour |
MAX_USER_CONNECTIONS | Number of simultaneous connections
that can be accepted from the same account; if it is 0,
max_connections will be used instead; if max_connections is
0, there is no limit for this account's simultaneous
connections. |
MAX_STATEMENT_TIME | Timeout, in seconds, for statements
executed by the user. See also Aborting Statements that
Exceed a Certain Time to Execute. |
If any of these limits are set to 0, then there is no limit
for that resource for that user.
To set resource limits for an account, if you do not want to
change that account's privileges, you can issue a GRANT
statement with the USAGE privilege, which has no meaning.
The statement can name some or all limit types, in any
order.
Here is an example showing how to set resource limits:
GRANT USAGE ON *.* TO 'someone'@'localhost' WITH
MAX_USER_CONNECTIONS 0
MAX_QUERIES_PER_HOUR 200;
The resources are tracked per account, which means
'user'@'server'; not per user name or per connection.
The count can be reset for all users using FLUSH
USER_RESOURCES, FLUSH PRIVILEGES or mysqladmin reload.
Per account resource limits are stored in the user table, in
the mysql database. Columns used for resources limits are
named max_questions, max_updates, max_connections (for
MAX_CONNECTIONS_PER_HOUR), and max_user_connections (for
MAX_USER_CONNECTIONS).
TLS Options
By default, MariaDB transmits data between the server and
clients without encrypting it. This is generally acceptable
when the server and client run on the same host or in
networks where security is guaranteed through other means.
However, in cases where the server and client exist on
separate networks or they are in a high-risk network, the
lack of encryption does introduce security concerns as a
malicious actor could potentially eavesdrop on the traffic
as it is sent over the network between them.
To mitigate this concern, MariaDB allows you to encrypt data
in transit between the server and clients using the
Transport Layer Security (TLS) protocol. TLS was formerly
known as Secure Socket Layer (SSL), but strictly speaking
the SSL protocol is a predecessor to TLS and, that version
of the protocol is now considered insecure. The
documentation still uses the term SSL often and for
compatibility reasons TLS-related server system and status
variables still use the prefix ssl_, but internally, MariaDB
only supports its secure successors.
See Secure Connections Overview for more information about
how to determine whether your MariaDB server has TLS
support.
You can set certain TLS-related restrictions for specific
user accounts. For instance, you might use this with user
accounts that require access to sensitive data while sending
it across networks that you do not control. These
restrictions can be enabled for a user account with the
CREATE USER, ALTER USER, or GRANT statements. The following
options are available:
Option | Description |
REQUIRE NONE | TLS is not required for this account, but can
still be used. |
REQUIRE SSL | The account must use TLS, but no valid X509
certificate is required. This option cannot be combined with
other TLS options. |
REQUIRE X509 | The account must use TLS and must have a
valid X509 certificate. This option implies REQUIRE SSL.
This option cannot be combined with other TLS options. |
REQUIRE ISSUER 'issuer' | The account must use TLS and
must have a valid X509 certificate. Also, the Certificate
Authority must be the one specified via the string issuer.
This option implies REQUIRE X509. This option can be
combined with the SUBJECT, and CIPHER options in any order.
|
REQUIRE SUBJECT 'subject' | The account must use TLS and
must have a valid X509 certificate. Also, the certificate's
Subject must be the one specified via the string subject.
This option implies REQUIRE X509. This option can be
combined with the ISSUER, and CIPHER options in any order. |
REQUIRE CIPHER 'cipher' | The account must use TLS, but no
valid X509 certificate is required. Also, the encryption
used for the connection must use one of the methods
specified in the string cipher. This option implies REQUIRE
SSL. This option can be combined with the ISSUER, and
SUBJECT options in any order. |
The REQUIRE keyword must be used only once for all specified
options, and the AND keyword can be used to separate
individual options, but it is not required.
For example, you can create a user account that requires
these TLS options with the following:
GRANT USAGE ON *.* TO 'alice'@'%'
REQUIRE SUBJECT '/CN=alice/O=My Dom,
Inc./C=US/ST=Oregon/L=Portland'
AND ISSUER '/C=FI/ST=Somewhere/L=City/ O=Some
Company/CN=Peter Parker/emailAddress=p.parker@marvel.com'
AND CIPHER 'TLSv1.2';
If any of these options are set for a specific user account,
then any client who tries to connect with that user account
will have to be configured to connect with TLS.
See Securing Connections for Client and Server for
information on how to enable TLS on the client and server.
Roles
Roles were introduced in MariaDB 10.0.5.
Syntax
------
GRANT role TO grantee [, grantee2 ... ]
[ WITH ADMIN OPTION ]
The GRANT statement is also used to grant the use a role to
one or more users or other roles. In order to be able to
grant a role, the grantor doing so must have permission to
do so (see WITH ADMIN in the CREATE ROLE article).
Specifying the WITH ADMIN OPTION permits the grantee to in
turn grant the role to another.
For example, the following commands show how to grant the
same role to a couple different users.
GRANT journalist TO hulda;
GRANT journalist TO berengar WITH ADMIN OPTION;
If a user has been granted a role, they do not automatically
obtain all permissions associated with that role. These
permissions are only in use when the user activates the role
with the SET ROLE statement.
Grant Examples
Granting Root-like Privileges
You can create a user that has privileges similar to the
default root accounts by executing the following:
CREATE USER 'alexander'@'localhost';
GRANT ALL PRIVILEGES ON *.* to 'alexander'@'localhost'
WITH GRANT OPTION;
URL: https://mariadb.com/kb/en/grant/ �ھ& �= { {&
RENAME USERSyntax
------
RENAME USER old_user TO new_user
[, old_user TO new_user] ...
Description
-----------
The RENAME USER statement renames existing MariaDB accounts.
To use it,
you must have the global CREATE USER privilege
or the UPDATE privilege for the mysql database.
Each account is named using the same format as for the
CREATE USER
statement; for example, 'jeffrey'@'localhost'.
If you specify only the user name part of the account name,
a host
name part of '%' is used.
If any of the old user accounts do not exist or any of the
new user accounts already
exist, ERROR 1396 (HY000) results. If an error occurs,
RENAME USER
will still rename the accounts that do not result in an
error.
Examples
--------
CREATE USER 'donald', 'mickey';
RENAME USER 'donald' TO 'duck'@'localhost', 'mickey'
TO 'mouse'@'localhost';
URL: https://mariadb.com/kb/en/rename-user/https://mariadb.com/kb/en/rename-user/ | �!
REVOKEPrivileges
Syntax
------
REVOKE
priv_type [(column_list)]
[, priv_type [(column_list)]] ...
ON [object_type] priv_level
FROM user [, user] ...
REVOKE ALL PRIVILEGES, GRANT OPTION
FROM user [, user] ...
Description
-----------
The REVOKE statement enables system administrators to revoke
privileges (or roles - see section below) from MariaDB
accounts. Each account is named using the same format
as for the GRANT statement; for example,
'jeffrey'@'localhost'. If you specify only the user name
part
of the account name, a host name part of '%' is used. For
details on the levels at which privileges exist, the
allowable
priv_type and priv_level values, and the
syntax for specifying users and passwords, see GRANT.
To use the first REVOKE syntax, you must have the
GRANT OPTION privilege, and you must have the privileges
that
you are revoking.
To revoke all privileges, use the second syntax, which drops
all
global, database, table, column, and routine privileges for
the named
user or users:
REVOKE ALL PRIVILEGES, GRANT OPTION FROM user [, user] ...
To use this REVOKE syntax, you must have the global
CREATE USER privilege or the
UPDATE privilege for the mysql database. See
GRANT.
Examples
--------
REVOKE SUPER ON *.* FROM 'alexander'@'localhost';
Roles
Roles were introduced in MariaDB 10.0.5.
Syntax
------
REVOKE role [, role ...]
FROM grantee [, grantee2 ... ]
Description
-----------
REVOKE is also used to remove a role from a user or another
role that it's previously been assigned to. If a role has
previously been set as a default role, REVOKE does not
remove the record of the default role from the mysql.user
table. If the role is subsequently granted again, it will
again be the user's default. Use SET DEFAULT ROLE NONE to
explicitly remove this.
Before MariaDB 10.1.13, the REVOKE role statement was not
permitted in prepared statements.
Example
REVOKE journalist FROM hulda
URL: https://mariadb.com/kb/en/revoke/https://mariadb.com/kb/en/revoke/ �
&
CREATE ROLERoles were introduced in MariaDB 10.0.5.
Syntax
------
CREATE [OR REPLACE] ROLE [IF NOT EXISTS] role
[WITH ADMIN
{CURRENT_USER | CURRENT_ROLE | user | role}]
Description
-----------
The CREATE ROLE statement creates one or more MariaDB roles.
To
use it, you must have the global CREATE USER
privilege or the INSERT privilege for the mysql
database. For each account, CREATE ROLE creates a new row in
the
mysql.user table that has no privileges, and with the
corresponding is_role field set to Y. It also creates a
record in the
mysql.roles_mapping table.
If any of the specified roles already exist, ERROR 1396
(HY000) results. If
an error occurs, CREATE ROLE will still create the roles
that do not result
in an error. The maximum length for a role is 128
characters. Role names can be
quoted, as explained in the Identifier names page. Only
one error is produced for all roles which have not been
created:
ERROR 1396 (HY000): Operation CREATE ROLE failed for
'a','b','c'
Failed CREATE or DROP operations, for both users and roles,
produce the
same error code.
PUBLIC and NONE are reserved, and cannot be used as role
names.
Before MariaDB 10.1.13, the CREATE ROLE statement was not
permitted in prepared statements.
For valid identifiers to use as role names, see Identifier
Names.
WITH ADMIN
The optional WITH ADMIN clause determines whether the
current user, the
current role or another user or role has use of the newly
created role. If the
clause is omitted, WITH ADMIN CURRENT_USER is treated as the
default, which
means that the current user will be able to GRANT this role
to
users.
OR REPLACE
The OR REPLACE clause was added in MariaDB 10.1.3
If the optional OR REPLACE clause is used, it acts as a
shortcut for:
DROP ROLE IF EXISTS name;
CREATE ROLE name ...;
IF NOT EXISTS
The IF NOT EXISTS clause was added in MariaDB 10.1.3
When the IF NOT EXISTS clause is used, MariaDB will return a
warning instead of an error if the specified role already
exists. Cannot be used together with the OR REPLACE clause.
Examples
--------
CREATE ROLE journalist;
CREATE ROLE developer WITH ADMIN lorinda;
The OR REPLACE and IF NOT EXISTS clauses:
CREATE ROLE journalist;
ERROR 1396 (HY000): Operation CREATE ROLE failed for
'journalist'
CREATE OR REPLACE ROLE journalist;
Query OK, 0 rows affected (0.00 sec)
CREATE ROLE IF NOT EXISTS journalist;
Query OK, 0 rows affected, 1 warning (0.00 sec)
SHOW WARNINGS;
+-------+------+---------------------------------------------------+
| Level | Code | Message |
+-------+------+---------------------------------------------------+
| Note | 1975 | Can't create role 'journalist'; it
already exists |
+-------+------+---------------------------------------------------+
URL: https://mariadb.com/kb/en/create-role/https://mariadb.com/kb/en/create-role/ � �. Assignment Operator (:=)Syntax
------
var_name := expr
Description
-----------
Assignment operator for assigning a value. The value on the
right is assigned to the variable on left.
Unlike the = operator, := can always be used to assign a
value to a variable.
This operator works with both user-defined variables and
local variables.
When assigning the same value to several variables,
LAST_VALUE() can be useful.
Examples
--------
SELECT @x := 10;
+----------+
| @x := 10 |
+----------+
| 10 |
+----------+
SELECT @x, @y := @x;
+------+----------+
| @x | @y := @x |
+------+----------+
| 10 | 10 |
+------+----------+
URL: https://mariadb.com/kb/en/assignment-operator/https://mariadb.com/kb/en/assignment-operator/ � �' GROUP_CONCATSyntax
------
GROUP_CONCAT(expr)
Description
-----------
This function returns a string result with the concatenated
non-NULL
values from a group. It returns NULL if there are no
non-NULL values.
The maximum returned length in bytes is determined by the
group_concat_max_len server system variable, which defaults
to 1M (>= MariaDB 10.2.4) or 1K (
URL: https://mariadb.com/kb/en/group_concat/https://mariadb.com/kb/en/group_concat/ � �& STDDEV_SAMPSyntax
------
STDDEV_SAMP(expr)
Description
-----------
Returns the sample standard deviation of expr (the square
root of VAR_SAMP()).
It is an aggregate function, and so can be used with the
GROUP BY clause.
From MariaDB 10.2.2, STDDEV_SAMP() can be used as a window
function.
STDDEV_SAMP() returns NULL if there were no matching rows.
URL: https://mariadb.com/kb/en/stddev_samp/https://mariadb.com/kb/en/stddev_samp/ �� � � ; �� ��xu �P } �'
SET PASSWORDSyntax
------
SET PASSWORD [FOR user] =
{
PASSWORD('some password')
| OLD_PASSWORD('some password')
| 'encrypted password'
}
Description
-----------
The SET PASSWORD statement assigns a password to an existing
MariaDB user
account.
If the password is specified using the PASSWORD() or
OLD_PASSWORD()
function, the literal text of the password should be given.
If the
password is specified without using either function, the
password
should be the already-encrypted password value as returned
by
PASSWORD().
OLD_PASSWORD() should only be used if your MariaDB/MySQL
clients are very old (< 4.0.0).
With no FOR clause, this statement sets the password for the
current
user. Any client that has connected to the server using a
non-anonymous
account can change the password for that account.
With a FOR clause, this statement sets the password for a
specific
account on the current server host. Only clients that have
the UPDATE
privilege for the mysql database can do this. The user value
should be
given in user_name@host_name format, where user_name and
host_name are
exactly as they are listed in the User and Host columns of
the
mysql.user table entry.
The argument to PASSWORD() and the password given to MariaDB
clients can be of arbitrary length.
Authentication Plugin Support
In MariaDB 10.4 and later, SET PASSWORD (with or without
PASSWORD()) works for accounts authenticated via any
authentication plugin that supports passwords stored in the
mysql.global_priv table.
The ed25519, mysql_native_password, and mysql_old_password
authentication plugins store passwords in the
mysql.global_priv table.
If you run SET PASSWORD on an account that authenticates
with one of these authentication plugins that stores
passwords in the mysql.global_priv table, then the
PASSWORD() function is evaluated by the specific
authentication plugin used by the account. The
authentication plugin hashes the password with a method that
is compatible with that specific authentication plugin.
The unix_socket, named_pipe, gssapi, and pam authentication
plugins do not store passwords in the mysql.global_priv
table. These authentication plugins rely on other methods to
authenticate the user.
If you attempt to run SET PASSWORD on an account that
authenticates with one of these authentication plugins that
doesn't store a password in the mysql.global_priv table,
then MariaDB Server will raise a warning like the following:
SET PASSWORD is ignored for users authenticating via
unix_socket plugin
See Authentication from MariaDB 10.4 for an overview of
authentication changes in MariaDB 10.4.
MariaDB until 10.3
In MariaDB 10.3 and before, SET PASSWORD (with or without
PASSWORD()) only works for accounts authenticated via
mysql_native_password or mysql_old_password authentication
plugins
Passwordless User Accounts
User accounts do not always require passwords to login.
The unix_socket , named_pipe and gssapi authentication
plugins do not require a password to authenticate the user.
The pam authentication plugin may or may not require a
password to authenticate the user, depending on the specific
configuration.
The mysql_native_password and mysql_old_password
authentication plugins require passwords for authentication,
but the password can be blank. In that case, no password is
required.
If you provide a password while attempting to log into the
server as an account that doesn't require a password, then
MariaDB server will simply ignore the password.
In MariaDB 10.4 and later, a user account can be defined to
use multiple authentication plugins in a specific order of
preference. This specific scenario may be more noticeable in
these versions, since an account could be associated with
some authentication plugins that require a password, and
some that do not.
Example
For example, if you had an entry with User and
Host column values of 'bob' and
'%.loc.gov', you would write the
statement like this:
SET PASSWORD FOR 'bob'@'%.loc.gov' =
PASSWORD('newpass');
URL: https://mariadb.com/kb/en/set-password/https://mariadb.com/kb/en/set-password/ � �$
DROP ROLERoles were introduced in MariaDB 10.0.5.
Syntax
------
DROP ROLE [IF EXISTS] role_name [,role_name ...]
Description
-----------
The DROP ROLE statement removes one or more MariaDB roles.
To use this
statement, you must have the global CREATE USER privilege or
the DELETE privilege for the mysql database.
DROP ROLE does not disable roles for connections which
selected them with SET ROLE. If a role has previously been
set as a default role, DROP ROLE does not remove the record
of the default role from the mysql.user table. If the role
is subsequently recreated and granted, it will again be the
user's default. Use SET DEFAULT ROLE NONE to explicitly
remove this.
If any of the specified user accounts do not exist, ERROR
1396 (HY000)
results. If an error occurs, DROP ROLE will still drop the
roles that
do not result in an error. Only one error is produced for
all roles which have not been dropped:
ERROR 1396 (HY000): Operation DROP ROLE failed for
'a','b','c'
Failed CREATE or DROP operations, for both users and roles,
produce the same error code.
Before MariaDB 10.1.13, the DROP ROLE statement was not
permitted in prepared statements.
IF EXISTS
The IF EXISTS clause was added in MariaDB 10.1.3
If the IF EXISTS clause is used, MariaDB will return a
warning instead of an error if the role does not exist.
Examples
--------
DROP ROLE journalist;
The same thing using the optional IF EXISTS clause:
DROP ROLE journalist;
ERROR 1396 (HY000): Operation DROP ROLE failed for
'journalist'
DROP ROLE IF EXISTS journalist;
Query OK, 0 rows affected, 1 warning (0.00 sec)
Note (Code 1975): Can't drop role 'journalist'; it
doesn't exist
URL: https://mariadb.com/kb/en/drop-role/https://mariadb.com/kb/en/drop-role/ � �$ BENCHMARKSyntax
------
BENCHMARK(count,expr)
Description
-----------
The BENCHMARK() function executes the expression expr
repeatedly count
times. It may be used to time how quickly MariaDB processes
the
expression. The result value is always 0. The intended use
is from
within the mysql client, which reports query execution
times.
Examples
--------
SELECT BENCHMARK(1000000,ENCODE('hello','goodbye'));
+----------------------------------------------+
| BENCHMARK(1000000,ENCODE('hello','goodbye')) |
+----------------------------------------------+
| 0 |
+----------------------------------------------+
1 row in set (0.21 sec)
URL: https://mariadb.com/kb/en/benchmark/https://mariadb.com/kb/en/benchmark/ � ^* BINLOG_GTID_POSFrom version 10.0.2, MariaDB supports global transaction IDs
for replication.
Syntax
------
BINLOG_GTID_POS(binlog_filename,binlog_offset)
Description
-----------
The BINLOG_GTID_POS() function takes as input an old-style
binary log position in the form of a file name and a file
offset. It looks up the position in the current binlog, and
returns a string representation of the corresponding GTID
position. If the position is not found in the current
binlog, NULL is returned.
Examples
--------
SELECT BINLOG_GTID_POS("master-bin.000001", 600);
URL: https://mariadb.com/kb/en/binlog_gtid_pos/https://mariadb.com/kb/en/binlog_gtid_pos/ � �$ COLLATIONSyntax
------
COLLATION(str)
Description
-----------
Returns the collation of the string argument. If str is not
a string, it is considered as a binary string (so the
function returns 'binary'). This applies to NULL, too. The
return value is a string in the utf8 character set.
See Character Sets and Collations.
Examples
--------
SELECT COLLATION('abc');
+-------------------+
| COLLATION('abc') |
+-------------------+
| latin1_swedish_ci |
+-------------------+
SELECT COLLATION(_utf8'abc');
+-----------------------+
| COLLATION(_utf8'abc') |
+-----------------------+
| utf8_general_ci |
+-----------------------+
URL: https://mariadb.com/kb/en/collation/https://mariadb.com/kb/en/collation/ � ��+�6� *���� �� ~ �)
Roles OverviewRoles were introduced in MariaDB 10.0.5.
Description
-----------
A role bundles a number of privileges together. It assists
larger organizations where, typically, a number of users
would have the same privileges, and, previously, the only
way to change the privileges for a group of users was by
changing each user's privileges individually.
Alternatively, multiple external users could have been
assigned the same user, and there would have been no way to
see which actual user was responsible for which action.
With roles, managing this is easy. For example, there could
be a number of users assigned to a journalist role, with
identical privileges. Changing the privileges for all the
journalists is a matter of simply changing the role's
privileges, while the individual user is still linked with
any changes that take place.
Roles are created with the CREATE ROLE statement, and
dropped with the DROP ROLE statement. Roles are then
assigned to a user with an extension to the GRANT statement,
while privileges are assigned to a role in the regular way
with GRANT. Similarly, the REVOKE statement can be used to
both revoke a role from a user, or revoke a privilege from a
role.
Once a user has connected, he can obtain all privileges
associated with a role by setting a role with the SET ROLE
statement. The CURRENT_ROLE function returns the currently
set role for the session, if any.
Only roles granted directly to a user can be set, roles
granted to other roles cannot. Instead the privileges
granted to a role, which is, in turn, granted to another
role (grantee), will be immediately available to any user
who sets this second grantee role.
Roles were implemented as a GSoC 2013 project by Vicentiu
Ciorbaru.
The SET DEFAULT ROLE statement allows one to set a default
role for a user. A default role is automatically enabled
when a user connects (an implicit SET ROLE statement is
executed immediately after a connection is established).
System Tables
Information about roles and who they've been granted to can
be found in the Information Schema APPLICABLE_ROLES table as
well as the mysql.ROLES_MAPPING table.
The Information Schema ENABLED_ROLES table shows the enabled
roles for the current session.
Examples
--------
Creating a role and granting a privilege:
CREATE ROLE journalist;
GRANT SHOW DATABASES ON *.* TO journalist;
GRANT journalist to hulda;
Note, that hulda has no SHOW DATABASES privilege, even
though she was granted the journalist role. She needs to set
the role first:
SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
+--------------------+
SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| NULL |
+--------------+
SET ROLE journalist;
SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| journalist |
+--------------+
SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| ... |
| information_schema |
| mysql |
| performance_schema |
| test |
| ... |
+--------------------+
SET ROLE NONE;
Roles can be granted to roles:
CREATE ROLE writer;
GRANT SELECT ON data.* TO writer;
GRANT writer TO journalist;
But one does not need to set a role granted to a role. For
example, hulda will automatically get all writer privileges
when she sets the journalist role:
SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| NULL |
+--------------+
SHOW TABLES FROM data;
Empty set (0.01 sec)
SET ROLE journalist;
SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| journalist |
+--------------+
SHOW TABLES FROM data;
+------------------------------+
| Tables_in_data |
+------------------------------+
| set1 |
| ... |
+------------------------------+
Roles and Views (and Stored Routines)
When a user sets a role, he, in a sense, has two identities
with two associated sets of privileges.
But a view (or a stored routine) can have only one definer.
So, when a view (or a stored routine) is created with the
SQL SECURITY DEFINER, one can specify whether the definer
should be CURRENT_USER (and the view will have none of the
privileges of the user's role) or CURRENT_ROLE (in this
case, the view will use role's privileges, but none of the
user's privileges). As a result, sometimes one can create a
view that is impossible to use.
CREATE ROLE r1;
GRANT ALL ON db1.* TO r1;
GRANT r1 TO foo@localhost;
GRANT ALL ON db.* TO foo@localhost;
SELECT CURRENT_USER
+---------------+
| current_user |
+---------------+
| foo@localhost |
+---------------+
SET ROLE r1;
CREATE TABLE db1.t1 (i int);
CREATE VIEW db.v1 AS SELECT * FROM db1.t1;
SHOW CREATE VIEW db.v1;
+------+------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
| View | Create View | character_set_client |
collation_connection |
+------+------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
| v1 | CREATE ALGORITHM=UNDEFINED DEFINER=`foo`@`localhost`
SQL SECURITY DEFINER VIEW `db`.`v1` AS SELECT `db1`.`t1`.`i`
AS `i` from `db1`.`t1` | utf8 | utf8_general_ci |
+------+------------------------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
CREATE DEFINER=CURRENT_ROLE VIEW db.v2 AS SELECT * FROM
db1.t1;
SHOW CREATE VIEW db.b2;
+------+-----------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
| View | Create View | character_set_client |
collation_connection |
+------+-----------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
| v2 | CREATE ALGORITHM=UNDEFINED DEFINER=`r1` SQL SECURITY
DEFINER VIEW `db`.`v2` AS select `db1`.`t1`.`a` AS `a` from
`db1`.`t1` | utf8 | utf8_general_ci |
+------+-----------------------------------------------------------------------------------------------------------------------------+----------------------+----------------------+
Other Resources
Roles Review by Peter Gulutzan
URL: https://mariadb.com/kb/en/roles_overview/https://mariadb.com/kb/en/roles_overview/ �
S( CONNECTION_IDSyntax
------
CONNECTION_ID()
Description
-----------
Returns the connection ID (thread ID) for the connection.
Every
thread (including events) has an ID that is unique among the
set of currently
connected clients.
Until MariaDB 10.3.1, returns MYSQL_TYPE_LONGLONG, or
bigint(10), in all cases. From MariaDB 10.3.1, returns
MYSQL_TYPE_LONG, or int(10), when the result would fit
within 32-bits.
Examples
--------
SELECT CONNECTION_ID();
+-----------------+
| CONNECTION_ID() |
+-----------------+
| 3 |
+-----------------+
URL: https://mariadb.com/kb/en/connection_id/https://mariadb.com/kb/en/connection_id/ � � ! SCHEMASyntax
------
SCHEMA()
Description
-----------
This function is a synonym for DATABASE().
URL: https://mariadb.com/kb/en/schema/https://mariadb.com/kb/en/schema/ u � �� ��d[� �e � �#
SET ROLERoles were introduced in MariaDB 10.0.5.
Syntax
------
SET ROLE { role | NONE }
Description
-----------
The SET ROLE statement enables a role, along with all of its
associated permissions, for the current session. To unset a
role, use NONE .
If a role that doesn't exist, or to which the user has not
been assigned, is specified, an ERROR 1959 (OP000): Invalid
role specification error occurs.
From MariaDB 10.1.1, an automatic SET ROLE is implicitly
performed when a user connects if that user has been
assigned a default role. See SET DEFAULT ROLE.
Example
SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| NULL |
+--------------+
SET ROLE staff;
SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| staff |
+--------------+
SET ROLE NONE;
Query OK, 0 rows affected (0.00 sec)
SELECT CURRENT_ROLE();
+----------------+
| CURRENT_ROLE() |
+----------------+
| NULL |
+----------------+
URL: https://mariadb.com/kb/en/set-role/https://mariadb.com/kb/en/set-role/ � $+
SET DEFAULT ROLEDefault roles were implemented in MariaDB 10.1.1.
Syntax
------
SET DEFAULT ROLE { role | NONE } [ FOR user@host ]
Description
-----------
The SET DEFAULT ROLE statement sets a default role for a
specified (or current) user. A default role is automatically
enabled when a user connects (an implicit SET ROLE statement
is executed immediately after a connection is established).
To be able to set a role as a default, one needs the
privileges to enable this role (if you cannot do SET ROLE X,
you won't be able to do SET DEFAULT ROLE X). To set a
default role for another user one needs to have write access
to the mysql database.
To remove a user's default role, use SET DEFAULT ROLE NONE
[ FOR user@host ]. The record of the default role is not
removed if the role is dropped or revoked, so if the role is
subsequently re-created or granted, it will again be the
user's default role.
The default role is stored in a new column in the mysql.user
table, and currently viewing this table is the only way to
see which role has been assigned to a user as the default.
Examples
--------
Setting a default role for the current user:
SET DEFAULT ROLE journalist;
Removing a default role from the current user:
SET DEFAULT ROLE NONE;
URL: https://mariadb.com/kb/en/set-default-role/https://mariadb.com/kb/en/set-default-role/ � �& AES_ENCRYPTSyntax
------
AES_ENCRYPT(str,key_str)
Description
-----------
AES_ENCRYPT() and AES_DECRYPT() allow encryption and
decryption of
data using the official AES (Advanced Encryption Standard)
algorithm,
previously known as "Rijndael." Encoding with a 128-bit
key length is
used, but you can extend it up to 256 bits by modifying the
source. We
chose 128 bits because it is much faster and it is secure
enough for
most purposes.
AES_ENCRYPT() encrypts a string str using the key key_str,
and returns a binary string.
AES_DECRYPT() decrypts the encrypted string and returns the
original
string.
The input arguments may be any length. If either argument is
NULL, the result of this function is also NULL.
Because AES is a block-level algorithm, padding is used to
encode
uneven length strings and so the result string length may be
calculated using this formula:
16 x (trunc(string_length / 16) + 1)
If AES_DECRYPT() detects invalid data or incorrect padding,
it returns
NULL. However, it is possible for AES_DECRYPT() to return a
non-NULL
value (possibly garbage) if the input data or the key is
invalid.
Examples
--------
INSERT INTO t VALUES
(AES_ENCRYPT('text',SHA2('password',512)));
URL: https://mariadb.com/kb/en/aes_encrypt/https://mariadb.com/kb/en/aes_encrypt/ � �# COMPRESSSyntax
------
COMPRESS(string_to_compress)
Description
-----------
Compresses a string and returns the result as a binary
string. This
function requires MariaDB to have been compiled with a
compression
library such as zlib. Otherwise, the return value is always
NULL. The
compressed string can be uncompressed with UNCOMPRESS().
The have_compress server system variable indicates whether a
compression library is present.
Examples
--------
SELECT LENGTH(COMPRESS(REPEAT('a',1000)));
+------------------------------------+
| LENGTH(COMPRESS(REPEAT('a',1000))) |
+------------------------------------+
| 21 |
+------------------------------------+
SELECT LENGTH(COMPRESS(''));
+----------------------+
| LENGTH(COMPRESS('')) |
+----------------------+
| 0 |
+----------------------+
SELECT LENGTH(COMPRESS('a'));
+-----------------------+
| LENGTH(COMPRESS('a')) |
+-----------------------+
| 13 |
+-----------------------+
SELECT LENGTH(COMPRESS(REPEAT('a',16)));
+----------------------------------+
| LENGTH(COMPRESS(REPEAT('a',16))) |
+----------------------------------+
| 15 |
+----------------------------------+
URL: https://mariadb.com/kb/en/compress/https://mariadb.com/kb/en/compress/ � � ' SESSION_USERSyntax
------
SESSION_USER()
Description
-----------
SESSION_USER() is a synonym for USER().
URL: https://mariadb.com/kb/en/session_user/https://mariadb.com/kb/en/session_user/ � � & SYSTEM_USERSyntax
------
SYSTEM_USER()
Description
-----------
SYSTEM_USER() is a synonym for USER().
URL: https://mariadb.com/kb/en/system_user/https://mariadb.com/kb/en/system_user/ � : $ <Syntax
------
URL: https://mariadb.com/kb/en/less-than/https://mariadb.com/kb/en/less-than/ � C - <=Syntax
------
URL: https://mariadb.com/kb/en/less-than-or-equal/https://mariadb.com/kb/en/less-than-or-equal/ � & BETWEEN ANDSyntax
------
expr BETWEEN min AND max
Description
-----------
If expr is greater than or equal to min and expr is less
than or equal
to max, BETWEEN returns 1, otherwise it returns 0. This is
equivalent
to the expression (min
URL: https://mariadb.com/kb/en/between-and/https://mariadb.com/kb/en/between-and/ � �# GREATESTSyntax
------
GREATEST(value1,value2,...)
Description
-----------
With two or more arguments, returns the largest
(maximum-valued)
argument. The arguments are compared using the same rules as
for
LEAST().
Examples
--------
SELECT GREATEST(2,0);
+---------------+
| GREATEST(2,0) |
+---------------+
| 2 |
+---------------+
SELECT GREATEST(34.0,3.0,5.0,767.0);
+------------------------------+
| GREATEST(34.0,3.0,5.0,767.0) |
+------------------------------+
| 767.0 |
+------------------------------+
SELECT GREATEST('B','A','C');
+-----------------------+
| GREATEST('B','A','C') |
+-----------------------+
| C |
+-----------------------+
URL: https://mariadb.com/kb/en/greatest/https://mariadb.com/kb/en/greatest/ � \# INTERVALSyntax
------
INTERVAL(N,N1,N2,N3,...)
Description
-----------
Returns the index of the last argument that is less than the
first argument or is NULL.
Returns 0 if N < N1, 1 if N < N2, 2 if N < N3 and so on or
-1 if N is NULL. All
arguments are treated as integers. It is required that N1 <
N2 < N3
URL: https://mariadb.com/kb/en/interval/https://mariadb.com/kb/en/interval/ � �& IS NOT NULLSyntax
------
IS NOT NULL
Description
-----------
Tests whether a value is not NULL. See also NULL Values in
MariaDB.
Examples
--------
SELECT 1 IS NOT NULL, 0 IS NOT NULL, NULL IS NOT NULL;
+---------------+---------------+------------------+
| 1 IS NOT NULL | 0 IS NOT NULL | NULL IS NOT NULL |
+---------------+---------------+------------------+
| 1 | 1 | 0 |
+---------------+---------------+------------------+
URL: https://mariadb.com/kb/en/is-not-null/https://mariadb.com/kb/en/is-not-null/ Q ��� iS�� vp �� �� ��� .?m 3A��I �� � ~& DES_DECRYPTSyntax
------
DES_DECRYPT(crypt_str[,key_str])
Description
-----------
Decrypts a string encrypted with DES_ENCRYPT(). If an error
occurs,
this function returns NULL.
This function works only if MariaDB has been configured with
TLS
support.
If no key_str argument is given, DES_DECRYPT() examines the
first byte
of the encrypted string to determine the DES key number that
was used
to encrypt the original string, and then reads the key from
the DES
key file to decrypt the message. For this to work, the user
must have
the SUPER privilege. The key file can be specified with the
--des-key-file server option.
If you pass this function a key_str argument, that string is
used as
the key for decrypting the message.
If the crypt_str argument does not appear to be an encrypted
string,
MariaDB returns the given crypt_str.
URL: https://mariadb.com/kb/en/des_decrypt/https://mariadb.com/kb/en/des_decrypt/ � r& DES_ENCRYPTSyntax
------
DES_ENCRYPT(str[,{key_num|key_str}])
Description
-----------
Encrypts the string with the given key using the Triple-DES
algorithm.
This function works only if MariaDB has been configured with
TLS support.
The encryption key to use is chosen based on the second
argument to
DES_ENCRYPT(), if one was given. With no argument, the first
key from
the DES key file is used. With a key_num argument, the given
key
number (0-9) from the DES key file is used. With a key_str
argument,
the given key string is used to encrypt str.
The key file can be specified with the --des-key-file server
option.
The return string is a binary string where the first
character is
CHAR(128 | key_num). If an error occurs, DES_ENCRYPT()
returns NULL.
The 128 is added to make it easier to recognize an encrypted
key. If
you use a string key, key_num is 127.
The string length for the result is given by this formula:
new_len = orig_len + (8 - (orig_len % 8)) + 1
Each line in the DES key file has the following format:
key_num des_key_str
Each key_num value must be a number in the range from 0 to
9. Lines in
the file may be in any order. des_key_str is the string that
is used
to encrypt the message. There should be at least one space
between the
number and the key. The first key is the default key that is
used if
you do not specify any key argument to DES_ENCRYPT().
You can tell MariaDB to read new key values from the key
file with the
FLUSH DES_KEY_FILE statement. This requires the RELOAD
privilege.
One benefit of having a set of default keys is that it gives
applications a way to check for the existence of encrypted
column
values, without giving the end user the right to decrypt
those values.
Examples
--------
SELECT customer_address FROM customer_table
WHERE crypted_credit_card =
DES_ENCRYPT('credit_card_number');
URL: https://mariadb.com/kb/en/des_encrypt/https://mariadb.com/kb/en/des_encrypt/ � ! ENCODESyntax
------
ENCODE(str,pass_str)
Description
-----------
ENCODE is not considered cryptographically secure, and
should not be used for password encryption.
Encrypt str using pass_str as the password. To decrypt the
result, use
DECODE().
The result is a binary string of the same length as str.
The strength of the encryption is based on how good the
random generator is.
It is not recommended to rely on the encryption performed by
the ENCODE function. Using a salt value (changed when a
password is updated) will improve matters somewhat, but for
storing passwords, consider a more cryptographically secure
function, such as SHA2().
Examples
--------
ENCODE('not so secret text',
CONCAT('random_salt','password'))
URL: https://mariadb.com/kb/en/encode/https://mariadb.com/kb/en/encode/ � �" ENCRYPTSyntax
------
ENCRYPT(str[,salt])
Description
-----------
Encrypts a string using the Unix crypt() system call,
returning an encrypted binary string. The salt argument
should be a string with at least two characters or the
returned result will be NULL. If no salt argument is given,
a random value of sufficient length is used.
It is not recommended to use ENCRYPT() with utf16, utf32 or
ucs2 multi-byte character sets because the crypt() system
call expects a string terminated with a zero byte.
Note that the underlying crypt() system call may have some
limitations, such as ignoring all but the first eight
characters.
If the have_crypt system variable is set to NO (because the
crypt() system call is not available), the ENCRYPT function
will always return NULL.
Examples
--------
SELECT ENCRYPT('encrypt me');
+-----------------------+
| ENCRYPT('encrypt me') |
+-----------------------+
| 4I5BsEx0lqTDk |
+-----------------------+
URL: https://mariadb.com/kb/en/encrypt/https://mariadb.com/kb/en/encrypt/ � C' OLD_PASSWORDSyntax
------
OLD_PASSWORD(str)
Description
-----------
OLD_PASSWORD() was added to MySQL when the implementation of
PASSWORD() was changed to improve security. OLD_PASSWORD()
returns the
value of the old (pre-MySQL 4.1) implementation of
PASSWORD() as a
string, and is intended to permit you to reset passwords for
any
pre-4.1 clients that need to connect to a more recent MySQL
server version, or any version of MariaDB,
without locking them out.
As of MariaDB 5.5, the return value is a nonbinary string in
the connection character set and collation, determined by
the values of the character_set_connection and
collation_connection system variables. Before 5.5, the
return value was a binary string.
The return value is 16 bytes in length, or NULL if the
argument was NULL.
URL: https://mariadb.com/kb/en/old_password/https://mariadb.com/kb/en/old_password/ � �! ISNULLSyntax
------
ISNULL(expr)
Description
-----------
If expr is NULL, ISNULL() returns 1, otherwise it returns 0.
See also NULL Values in MariaDB.
Examples
--------
SELECT ISNULL(1+1);
+-------------+
| ISNULL(1+1) |
+-------------+
| 0 |
+-------------+
SELECT ISNULL(1/0);
+-------------+
| ISNULL(1/0) |
+-------------+
| 1 |
+-------------+
URL: https://mariadb.com/kb/en/isnull/https://mariadb.com/kb/en/isnull/ � �. Operator PrecedenceThe precedence is the order in which the SQL operators are
evaluated.
The following list shows the SQL operator precedence.
Operators that appear first in the list have a higher
precedence. Operators which are listed together have the
same precedence.
INTERVAL
BINARY, COLLATE
!
- (unary minus), [[bitwise-not|]] (unary bit inversion)
|| (string concatenation)
^
*, /, DIV, %, MOD
-, +
&
|
= (comparison), , >=, >,
URL: https://mariadb.com/kb/en/operator-precedence/https://mariadb.com/kb/en/operator-precedence/ � �& &Syntax
------
&
Description
-----------
Bitwise AND. Converts the values to binary and compares
bits. Only if both the corresponding bits are 1 is the
resulting bit also 1.
See also bitwise OR.
Examples
--------
SELECT 2&1;
+-----+
| 2&1 |
+-----+
| 0 |
+-----+
SELECT 3&1;
+-----+
| 3&1 |
+-----+
| 1 |
+-----+
SELECT 29 & 15;
+---------+
| 29 & 15 |
+---------+
| 13 |
+---------+
URL: https://mariadb.com/kb/en/bitwise_and/https://mariadb.com/kb/en/bitwise_and/ � B % <<Syntax
------
value1
URL: https://mariadb.com/kb/en/shift-left/https://mariadb.com/kb/en/shift-left/ f } d='n����&z J�� ��6� �v � = SHA1Syntax
------
SHA1(str), SHA(str)
Description
-----------
Calculates an SHA-1 160-bit checksum for the string str, as
described in
RFC 3174 (Secure Hash Algorithm).
The value is returned as a string of 40 hex digits, or NULL
if the argument was NULL. As of MariaDB 5.5, the return
value is a nonbinary string in the connection character set
and collation, determined by the values of the
character_set_connection and collation_connection system
variables. Before 5.5, the return value was a binary string.
Examples
--------
SELECT SHA1('some boring text');
+------------------------------------------+
| SHA1('some boring text') |
+------------------------------------------+
| af969fc2085b1bb6d31e517d5c456def5cdd7093 |
+------------------------------------------+
URL: https://mariadb.com/kb/en/sha1/https://mariadb.com/kb/en/sha1/ � � SHA2SHA2() was introduced in MariaDB 5.5
Syntax
------
SHA2(str,hash_len)
Description
-----------
Given a string str, calculates an SHA-2 checksum, which is
considered more cryptographically secure than its SHA-1
equivalent. The SHA-2 family includes SHA-224, SHA-256,
SHA-384, and SHA-512, and the hash_len must correspond to
one of these, i.e. 224, 256, 384 or 512. 0 is equivalent to
256.
The return value is a nonbinary string in the connection
character set and collation, determined by the values of the
character_set_connection and collation_connection system
variables.
NULL is returned if the hash length is not valid, or the
string str is NULL.
SHA2 will only work if MariaDB was has been configured with
TLS support.
Examples
--------
SELECT SHA2('Maria',224);
+----------------------------------------------------------+
| SHA2('Maria',224) |
+----------------------------------------------------------+
| 6cc67add32286412efcab9d0e1675a43a5c2ef3cec8879f81516ff83 |
+----------------------------------------------------------+
SELECT SHA2('Maria',256);
+------------------------------------------------------------------+
| SHA2('Maria',256) |
+------------------------------------------------------------------+
|
9ff18ebe7449349f358e3af0b57cf7a032c1c6b2272cb2656ff85eb112232f16
|
+------------------------------------------------------------------+
SELECT SHA2('Maria',0);
+------------------------------------------------------------------+
| SHA2('Maria',0) |
+------------------------------------------------------------------+
|
9ff18ebe7449349f358e3af0b57cf7a032c1c6b2272cb2656ff85eb112232f16
|
+------------------------------------------------------------------+
URL: https://mariadb.com/kb/en/sha2/https://mariadb.com/kb/en/sha2/ �
`% UNCOMPRESSSyntax
------
UNCOMPRESS(string_to_uncompress)
Description
-----------
Uncompresses a string compressed by the COMPRESS() function.
If the
argument is not a compressed value, the result is NULL. This
function
requires MariaDB to have been compiled with a compression
library such
as zlib. Otherwise, the return value is always NULL. The
have_compress server system variable indicates whether a
compression library is present.
Examples
--------
SELECT UNCOMPRESS(COMPRESS('a string'));
+----------------------------------+
| UNCOMPRESS(COMPRESS('a string')) |
+----------------------------------+
| a string |
+----------------------------------+
SELECT UNCOMPRESS('a string');
+------------------------+
| UNCOMPRESS('a string') |
+------------------------+
| NULL |
+------------------------+
URL: https://mariadb.com/kb/en/uncompress/https://mariadb.com/kb/en/uncompress/ � . UNCOMPRESSED_LENGTHSyntax
------
UNCOMPRESSED_LENGTH(compressed_string)
Description
-----------
Returns the length that the compressed string had before
being
compressed with COMPRESS().
UNCOMPRESSED_LENGTH() returns NULL or an incorrect result if
the string is not compressed.
Until MariaDB 10.3.1, returns MYSQL_TYPE_LONGLONG, or
bigint(10), in all cases. From MariaDB 10.3.1, returns
MYSQL_TYPE_LONG, or int(10), when the result would fit
within 32-bits.
Examples
--------
SELECT UNCOMPRESSED_LENGTH(COMPRESS(REPEAT('a',30)));
+-----------------------------------------------+
| UNCOMPRESSED_LENGTH(COMPRESS(REPEAT('a',30))) |
+-----------------------------------------------+
| 30 |
+-----------------------------------------------+
URL: https://mariadb.com/kb/en/uncompressed_length/https://mariadb.com/kb/en/uncompressed_length/ �
�% INET6_ATONINET6_ATON() has been available since MariaDB 10.0.12.
Syntax
------
INET6_ATON(expr)
Description
-----------
Given an IPv6 or IPv4 network address as a string, returns a
binary string that represents the numeric value of the
address.
No trailing zone ID's or traling network masks are
permitted. For IPv4 addresses, or IPv6 addresses with IPv4
address parts, no classful addresses or trailing port
numbers are permitted and octal numbers are not supported.
The returned binary string will be VARBINARY(16) or
VARBINARY(4) for IPv6 and IPv4 addresses respectively.
Returns NULL if the argument is not understood.
Examples
--------
SELECT HEX(INET6_ATON('10.0.1.1'));
+-----------------------------+
| HEX(INET6_ATON('10.0.1.1')) |
+-----------------------------+
| 0A000101 |
+-----------------------------+
SELECT HEX(INET6_ATON('48f3::d432:1431:ba23:846f'));
+----------------------------------------------+
| HEX(INET6_ATON('48f3::d432:1431:ba23:846f')) |
+----------------------------------------------+
| 48F3000000000000D4321431BA23846F |
+----------------------------------------------+
URL: https://mariadb.com/kb/en/inet6_aton/https://mariadb.com/kb/en/inet6_aton/ � +& >>Syntax
------
value1 >> value2
Description
-----------
Converts a longlong (BIGINT) number (value1) to binary and
shifts value2 units to the right.
Examples
--------
SELECT 4 >> 2;
+--------+
| 4 >> 2 |
+--------+
| 1 |
+--------+
URL: https://mariadb.com/kb/en/shift-right/https://mariadb.com/kb/en/shift-right/ � �$ BIT_COUNTSyntax
------
BIT_COUNT(N)
Description
-----------
Returns the number of bits that are set in the argument N.
Examples
--------
SELECT BIT_COUNT(29), BIT_COUNT(b'101010');
+---------------+----------------------+
| BIT_COUNT(29) | BIT_COUNT(b'101010') |
+---------------+----------------------+
| 4 | 3 |
+---------------+----------------------+
URL: https://mariadb.com/kb/en/bit_count/https://mariadb.com/kb/en/bit_count/ � �& ^Syntax
------
^
Description
-----------
Bitwise XOR. Converts the values to binary and compares
bits. If one (and only one) of the corresponding bits is 1
is the resulting bit also 1.
Examples
--------
SELECT 1 ^ 1;
+-------+
| 1 ^ 1 |
+-------+
| 0 |
+-------+
SELECT 1 ^ 0;
+-------+
| 1 ^ 0 |
+-------+
| 1 |
+-------+
SELECT 11 ^ 3;
+--------+
| 11 ^ 3 |
+--------+
| 8 |
+--------+
URL: https://mariadb.com/kb/en/bitwise-xor/https://mariadb.com/kb/en/bitwise-xor/ � �% |Syntax
------
|
Description
-----------
Bitwise OR. Converts the values to binary and compares bits.
If either of the corresponding bits has a value of 1, the
resulting bit is also 1.
See also bitwise AND.
Examples
--------
SELECT 2|1;
+-----+
| 2|1 |
+-----+
| 3 |
+-----+
SELECT 29 | 15;
+---------+
| 29 | 15 |
+---------+
| 31 |
+---------+
URL: https://mariadb.com/kb/en/bitwise-or/https://mariadb.com/kb/en/bitwise-or/ ��� ��Pg��!m�
�z
nen�L �� �
# GET_LOCKSyntax
------
GET_LOCK(str,timeout)
Description
-----------
Tries to obtain a lock with a name given by the string str,
using a timeout of timeout seconds. Returns 1 if the lock
was obtained successfully, 0 if the attempt timed out (for
example, because another client has previously locked the
name), or NULL if an error occurred (such as running out of
memory or the thread was killed with mysqladmin kill).
A lock is released with RELEASE_LOCK(), when the connection
terminates (either normally or abnormally), or before
MariaDB 10.0.2, when the connection executes another
GET_LOCK statement. From MariaDB 10.0.2, a connection can
hold multiple locks at the same time, so a lock that is no
longer needed needs to be explicitly released.
The IS_FREE_LOCK function returns whether a specified lock a
free or not, and the IS_USED_LOCK whether the function is in
use or not.
Locks obtained with GET_LOCK() do not interact with
transactions. That is, committing a transaction does not
release any such locks obtained during the transaction.
From MariaDB 10.0.2, it is also possible to recursively set
the same lock. If a lock with the same name is set n times,
it needs to be released n times as well.
str is case insensitive for GET_LOCK() and related
functions. If str is an empty string or NULL, GET_LOCK()
returns NULL and does nothing. From MariaDB 10.2.2, timeout
supports microseconds. Before then, it was rounded to the
closest integer.
If the metadata_lock_info plugin is installed, locks
acquired with this function are visible in the Information
Schema METADATA_LOCK_INFO table.
This function can be used to implement application locks or
to simulate record locks. Names are locked on a server-wide
basis. If a name has been locked by one client, GET_LOCK()
blocks any request by another client for a lock with the
same name. This allows clients that agree on a given lock
name to use the name to perform cooperative advisory
locking. But be aware that it also allows a client that is
not among the set of cooperating clients to lock a name,
either inadvertently or deliberately, and thus prevent any
of the cooperating clients from locking that name. One way
to reduce the likelihood of this is to use lock names that
are database-specific or application-specific. For example,
use lock names of the form db_name.str or app_name.str.
Statements using the GET_LOCK() function are not safe for
replication.
The patch to permit multiple locks was contributed by
Konstantin "Kostja" Osipov (MDEV-3917).
Examples
--------
SELECT GET_LOCK('lock1',10);
+----------------------+
| GET_LOCK('lock1',10) |
+----------------------+
| 1 |
+----------------------+
SELECT IS_FREE_LOCK('lock1'), IS_USED_LOCK('lock1');
+-----------------------+-----------------------+
| IS_FREE_LOCK('lock1') | IS_USED_LOCK('lock1') |
+-----------------------+-----------------------+
| 0 | 46 |
+-----------------------+-----------------------+
SELECT IS_FREE_LOCK('lock2'), IS_USED_LOCK('lock2');
+-----------------------+-----------------------+
| IS_FREE_LOCK('lock2') | IS_USED_LOCK('lock2') |
+-----------------------+-----------------------+
| 1 | NULL |
+-----------------------+-----------------------+
From MariaDB 10.0.2, multiple locks can be held:
SELECT GET_LOCK('lock2',10);
+----------------------+
| GET_LOCK('lock2',10) |
+----------------------+
| 1 |
+----------------------+
SELECT IS_FREE_LOCK('lock1'), IS_FREE_LOCK('lock2');
+-----------------------+-----------------------+
| IS_FREE_LOCK('lock1') | IS_FREE_LOCK('lock2') |
+-----------------------+-----------------------+
| 0 | 0 |
+-----------------------+-----------------------+
SELECT RELEASE_LOCK('lock1'), RELEASE_LOCK('lock2');
+-----------------------+-----------------------+
| RELEASE_LOCK('lock1') | RELEASE_LOCK('lock2') |
+-----------------------+-----------------------+
| 1 | 1 |
+-----------------------+-----------------------+
Before MariaDB 10.0.2, a connection could only hold a single
lock:
SELECT GET_LOCK('lock2',10);
+----------------------+
| GET_LOCK('lock2',10) |
+----------------------+
| 1 |
+----------------------+
SELECT IS_FREE_LOCK('lock1'), IS_FREE_LOCK('lock2');
+-----------------------+-----------------------+
| IS_FREE_LOCK('lock1') | IS_FREE_LOCK('lock2') |
+-----------------------+-----------------------+
| 1 | 0 |
+-----------------------+-----------------------+
SELECT RELEASE_LOCK('lock1'), RELEASE_LOCK('lock2');
+-----------------------+-----------------------+
| RELEASE_LOCK('lock1') | RELEASE_LOCK('lock2') |
+-----------------------+-----------------------+
| NULL | 1 |
+-----------------------+-----------------------+
From MariaDB 10.0.2, it is possible to hold the same lock
recursively. This example is viewed using the
metadata_lock_info plugin:
SELECT GET_LOCK('lock3',10);
+----------------------+
| GET_LOCK('lock3',10) |
+----------------------+
| 1 |
+----------------------+
SELECT GET_LOCK('lock3',10);
+----------------------+
| GET_LOCK('lock3',10) |
+----------------------+
| 1 |
+----------------------+
SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO;
+-----------+---------------------+---------------+-----------+--------------+------------+
| THREAD_ID | LOCK_MODE | LOCK_DURATION | LOCK_TYPE |
TABLE_SCHEMA | TABLE_NAME |
+-----------+---------------------+---------------+-----------+--------------+------------+
| 46 | MDL_SHARED_NO_WRITE | NULL | User lock | lock3 | |
+-----------+---------------------+---------------+-----------+--------------+------------+
SELECT RELEASE_LOCK('lock3');
+-----------------------+
| RELEASE_LOCK('lock3') |
+-----------------------+
| 1 |
+-----------------------+
SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO;
+-----------+---------------------+---------------+-----------+--------------+------------+
| THREAD_ID | LOCK_MODE | LOCK_DURATION | LOCK_TYPE |
TABLE_SCHEMA | TABLE_NAME |
+-----------+---------------------+---------------+-----------+--------------+------------+
| 46 | MDL_SHARED_NO_WRITE | NULL | User lock | lock3 | |
+-----------+---------------------+---------------+-----------+--------------+------------+
SELECT RELEASE_LOCK('lock3');
+-----------------------+
| RELEASE_LOCK('lock3') |
+-----------------------+
| 1 |
+-----------------------+
SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO;
Empty set (0.000 sec)
Timeout example: Connection 1:
SELECT GET_LOCK('lock4',10);
+----------------------+
| GET_LOCK('lock4',10) |
+----------------------+
| 1 |
+----------------------+
Connection 2:
SELECT GET_LOCK('lock4',10);
After 10 seconds...
+----------------------+
| GET_LOCK('lock4',10) |
+----------------------+
| 0 |
+----------------------+
Deadlocks are automatically detected and resolved.
Connection 1:
SELECT GET_LOCK('lock5',10);
+----------------------+
| GET_LOCK('lock5',10) |
+----------------------+
| 1 |
+----------------------+
Connection 2:
SELECT GET_LOCK('lock6',10);
+----------------------+
| GET_LOCK('lock6',10) |
+----------------------+
| 1 |
+----------------------+
Connection 1:
SELECT GET_LOCK('lock6',10);
+----------------------+
| GET_LOCK('lock6',10) |
+----------------------+
| 0 |
+----------------------+
Connection 2:
SELECT GET_LOCK('lock5',10);
ERROR 1213 (40001): Deadlock found when trying to get lock;
try restarting transaction
URL: https://mariadb.com/kb/en/get_lock/https://mariadb.com/kb/en/get_lock/ C �ܫ�
�U �
!% INET6_NTOAINET6_NTOA() has been available from MariaDB 10.0.12.
Syntax
------
INET6_NTOA(expr)
Description
-----------
Given an IPv6 or IPv4 network address as a numeric binary
string, returns the address as a nonbinary string in the
connection character set.
The return string is lowercase, and is platform independent,
since it does not use functions specific to the operating
system. It has a maximum length of 39 characters.
Returns NULL if the argument is not understood.
Examples
--------
SELECT INET6_NTOA(UNHEX('0A000101'));
+-------------------------------+
| INET6_NTOA(UNHEX('0A000101')) |
+-------------------------------+
| 10.0.1.1 |
+-------------------------------+
SELECT
INET6_NTOA(UNHEX('48F3000000000000D4321431BA23846F'));
+-------------------------------------------------------+
| INET6_NTOA(UNHEX('48F3000000000000D4321431BA23846F')) |
+-------------------------------------------------------+
| 48f3::d432:1431:ba23:846f |
+-------------------------------------------------------+
URL: https://mariadb.com/kb/en/inet6_ntoa/https://mariadb.com/kb/en/inet6_ntoa/ � �" IS_IPV4IS_IPV4() has been available since MariaDB 10.0.12.
Syntax
------
IS_IPV4(expr)
Description
-----------
If the expression is a valid IPv4 address, returns 1,
otherwise returns 0.
IS_IPV4() is stricter than INET_ATON(), but as strict as
INET6_ATON(), in determining the validity of an IPv4
address. This implies that if IS_IPV4 returns 1, the same
expression will always return a non-NULL result when passed
to INET_ATON(), but that the reverse may not apply.
Examples
--------
SELECT IS_IPV4('1110.0.1.1');
+-----------------------+
| IS_IPV4('1110.0.1.1') |
+-----------------------+
| 0 |
+-----------------------+
SELECT IS_IPV4('48f3::d432:1431:ba23:846f');
+--------------------------------------+
| IS_IPV4('48f3::d432:1431:ba23:846f') |
+--------------------------------------+
| 0 |
+--------------------------------------+
URL: https://mariadb.com/kb/en/is_ipv4/https://mariadb.com/kb/en/is_ipv4/ � �) IS_IPV4_COMPATIS_IPV4_COMPAT() has been available since MariaDB 10.0.12.
Syntax
------
IS_IPV4_COMPAT(expr)
Description
-----------
Returns 1 if a given numeric binary string IPv6 address,
such as returned by INET6_ATON(), is IPv4-compatible,
otherwise returns 0.
Examples
--------
SELECT IS_IPV4_COMPAT(INET6_ATON('::10.0.1.1'));
+------------------------------------------+
| IS_IPV4_COMPAT(INET6_ATON('::10.0.1.1')) |
+------------------------------------------+
| 1 |
+------------------------------------------+
SELECT
IS_IPV4_COMPAT(INET6_ATON('::48f3::d432:1431:ba23:846f'));
+-----------------------------------------------------------+
|
IS_IPV4_COMPAT(INET6_ATON('::48f3::d432:1431:ba23:846f'))
|
+-----------------------------------------------------------+
| 0 |
+-----------------------------------------------------------+
URL: https://mariadb.com/kb/en/is_ipv4_compat/https://mariadb.com/kb/en/is_ipv4_compat/ � T) IS_IPV4_MAPPEDIS_IPV4_MAPPED() has been available since MariaDB 10.0.12.
Syntax
------
IS_IPV4_MAPPED(expr)
Description
-----------
Returns 1 if a given a numeric binary string IPv6 address,
such as returned by INET6_ATON(), is a valid IPv4-mapped
address, otherwise returns 0.
Examples
--------
SELECT IS_IPV4_MAPPED(INET6_ATON('::10.0.1.1'));
+------------------------------------------+
| IS_IPV4_MAPPED(INET6_ATON('::10.0.1.1')) |
+------------------------------------------+
| 0 |
+------------------------------------------+
SELECT IS_IPV4_MAPPED(INET6_ATON('::ffff:10.0.1.1'));
+-----------------------------------------------+
| IS_IPV4_MAPPED(INET6_ATON('::ffff:10.0.1.1')) |
+-----------------------------------------------+
| 1 |
+-----------------------------------------------+
URL: https://mariadb.com/kb/en/is_ipv4_mapped/https://mariadb.com/kb/en/is_ipv4_mapped/ � Q* MASTER_POS_WAITMASTER_POS_WAIT was introduced in MariaDB 10.0.9.
Syntax
------
MASTER_POS_WAIT(log_name,log_pos[,timeout,["connection_name"]])
Description
-----------
This function is useful in replication for controlling
master/slave synchronization. It blocks until the slave has
read and applied all updates up to the specified position
(log_name,log_pos) in the master log. The return value is
the number of log events the slave had to wait for to
advance to the specified position. The function returns NULL
if
the slave SQL thread is not started, the slave's master
information is not
initialized, the arguments are incorrect, or an error
occurs. It returns -1 if
the timeout has been exceeded. If the slave SQL thread stops
while
MASTER_POS_WAIT() is waiting, the function returns NULL. If
the slave is past the specified position, the function
returns immediately.
If a timeout value is specified, MASTER_POS_WAIT() stops
waiting when timeout seconds have elapsed. timeout must be
greater than 0; a
zero or negative timeout means no timeout.
The connection_name is used when you are using
multi-source-replication. If you don't specify it, it's
set to the value of the default_master_connection system
variable.
Statements using the MASTER_POS_WAIT() function are not safe
for replication.
URL: https://mariadb.com/kb/en/master_pos_wait/https://mariadb.com/kb/en/master_pos_wait/ � J& ~Syntax
------
~
Description
-----------
Bitwise NOT. Converts the value to 4 bytes binary and
inverts all bits.
Examples
--------
SELECT 3 & ~1;
+--------+
| 3 & ~1 |
+--------+
| 2 |
+--------+
SELECT 5 & ~1;
+--------+
| 5 & ~1 |
+--------+
| 4 |
+--------+
URL: https://mariadb.com/kb/en/bitwise-not/https://mariadb.com/kb/en/bitwise-not/ �
�% TRUE FALSEDescription
-----------
The constants TRUE and FALSE evaluate to 1 and 0,
respectively. The
constant names can be written in any lettercase.
Examples
--------
SELECT TRUE, true, FALSE, false;
+------+------+-------+-------+
| TRUE | TRUE | FALSE | FALSE |
+------+------+-------+-------+
| 1 | 1 | 0 | 0 |
+------+------+-------+-------+
URL: https://mariadb.com/kb/en/true-false/https://mariadb.com/kb/en/true-false/ �
�% CHECK VIEWCHECK VIEW was introduced in MariaDB 10.0.18.
Syntax
------
CHECK VIEW view_name
Description
-----------
The CHECK VIEW statement was introduced in MariaDB 10.0.18
to assist with fixing MDEV-6916, an issue introduced in
MariaDB 5.2 where the view algorithms were swapped. It
checks whether the view algorithm is correct. It is run as
part of mysql_upgrade, and should not normally be required
in regular use.
URL: https://mariadb.com/kb/en/check-view/https://mariadb.com/kb/en/check-view/ � . ) URL: https://mariadb.com/kb/en/checksum-table/https://mariadb.com/kb/en/checksum-table/
H3 BLOB and TEXT Data TypesDescription
-----------
A BLOB is a binary large object that can hold a variable
amount of
data. The four BLOB types are
TINYBLOB,
BLOB,
MEDIUMBLOB, and
LONGBLOB.
These differ only in the maximum length of the values they
can hold.
The TEXT types are
TINYTEXT,
TEXT,
MEDIUMTEXT, and
LONGTEXT.
JSON (alias for LONGTEXT)
These correspond to the four BLOB types and have the same
maximum lengths and storage requirements.
Starting from MariaDB 10.2.1, BLOB and TEXT columns can have
a DEFAULT value.
URL: https://mariadb.com/kb/en/blob-and-text-data-types/https://mariadb.com/kb/en/blob-and-text-data-types/ ��zd p
�� ��� �'�j� ^yZ� � � �+ MASTER_GTID_WAITMASTER_GTID_WAIT() was included in MariaDB 10.0.9.
Syntax
------
MASTER_GTID_WAIT(gtid-list[, timeout)
Description
-----------
This function takes a string containing a comma-separated
list of global transaction id's
(similar to the value of, for example, gtid_binlog_pos). It
waits until the value of gtid_slave_pos has the same or
higher seq_no within all replication domains specified in
the gtid-list; in other words, it waits until the slave has
reached the specified GTID position.
An optional second argument gives a timeout in seconds. If
the timeout
expires before the specified GTID position is reached, then
the function
returns -1. Passing NULL or a negative number for the
timeout means no timeout, and the function will wait
indefinitely.
If the wait completes without a timeout, 0 is returned.
Passing NULL for the
gtid-list makes the function return NULL immediately,
without waiting.
The gtid-list may be the empty string, in which case
MASTER_GTID_WAIT()
returns immediately. If the gtid-list contains fewer domains
than
gtid_slave_pos, then only those domains are waited upon. If
gtid-list
contains a domain that is not present in @@gtid_slave_pos,
then
MASTER_GTID_WAIT() will wait until an event containing such
domain_id arrives
on the slave (or until timed out or killed).
MASTER_GTID_WAIT() can be useful to ensure that a slave has
caught up to
a master. Simply take the value of gtid_binlog_pos on the
master, and use it in a MASTER_GTID_WAIT() call on the
slave; when the call completes, the slave
will have caught up with that master position.
MASTER_GTID_WAIT() can also be used in client applications
together with the
last_gtid session variable. This is useful in a
read-scaleout replication setup, where the application
writes to a single master but divides the
reads out to a number of slaves to distribute the load. In
such a setup, there
is a risk that an application could first do an update on
the master, and then
a bit later do a read on a slave, and if the slave is not
fast enough, the
data read from the slave might not include the update just
made, possibly
confusing the application and/or the end-user. One way to
avoid this is to
request the value of last_gtid on the master just after the
update. Then
before doing the read on the slave, do a MASTER_GTID_WAIT()
on the value
obtained from the master; this will ensure that the read is
not performed
until the slave has replicated sufficiently far for the
update to have become
visible.
Note that MASTER_GTID_WAIT() can be used even if the slave
is configured not
to use GTID for connections (CHANGE MASTER TO
master_use_gtid=no). This is
because from MariaDB 10, GTIDs are always logged on the
master server, and
always recorded on the slave servers.
Differences to MASTER_POS_WAIT()
MASTER_GTID_WAIT() is global; it waits for any master
connection to reach
the specified GTID position. MASTER_POS_WAIT() works only
against a
specific connection. This also means that while
MASTER_POS_WAIT() aborts if
its master connection is terminated with STOP SLAVE or due
to an error,
MASTER_GTID_WAIT() continues to wait while slaves are
stopped.
MASTER_GTID_WAIT() can take its timeout as a floating-point
value, so a
timeout in fractional seconds is supported, eg.
MASTER_GTID_WAIT("0-1-100",
0.5). (The minimum wait is one microsecond, 0.000001
seconds).
MASTER_GTID_WAIT() allows one to specify a timeout of zero
in order to do a
non-blocking check to see if the slaves have progressed to
a specific GTID position
(MASTER_POS_WAIT() takes a zero timeout as meaning an
infinite wait). To do
an infinite MASTER_GTID_WAIT(), specify a negative timeout,
or omit the
timeout argument.
MASTER_GTID_WAIT() does not return the number of events
executed since the
wait started, nor does it return NULL if a slave thread is
stopped. It
always returns either 0 for successful wait completed, or
-1 for timeout
reached (or NULL if the specified gtid-pos is NULL).
Since MASTER_GTID_WAIT() looks only at the seq_no part of
the GTIDs, not the
server_id, care is needed if a slave becomes diverged from
another server so
that two different GTIDs with the same seq_no (in the same
domain) arrive at
the same server. This situation is in any case best avoided;
setting
gtid_strict_mode is recommended, as this will prevent any
such out-of-order sequence numbers from ever being
replicated on a slave.
URL: https://mariadb.com/kb/en/master_gtid_wait/https://mariadb.com/kb/en/master_gtid_wait/ � � UUIDSyntax
------
UUID()
Description
-----------
Returns a Universal Unique Identifier (UUID) generated
according to "DCE 1.1:
Remote Procedure Call" (Appendix A) CAE (Common
Applications Environment)
Specifications published by The Open Group in October
1997
(Document Number C706).
A UUID is designed as a number that is globally unique in
space and time. Two
calls to UUID() are expected to generate two different
values, even if these calls are performed on two separate
computers that are
not connected to each other.
A UUID is a 128-bit number represented by a utf8 string of
five
hexadecimal numbers in aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee
format:
The first three numbers are generated from a timestamp.
The fourth number preserves temporal uniqueness in case the
timestamp value
loses monotonicity (for example, due to daylight saving
time).
The fifth number is an IEEE 802 node number that provides
spatial uniqueness.
A random number is substituted if the latter is not
available (for example,
because the host computer has no Ethernet card, or we do
not know how to find
the hardware address of an interface on your operating
system). In this case,
spatial uniqueness cannot be guaranteed. Nevertheless, a
collision should
have very low probability.
Currently, the MAC address of an interface is taken into
account only on FreeBSD and Linux. On other operating
systems, MariaDB uses a randomly generated 48-bit number.
Statements using the UUID() function are not safe for
replication.
UUID() results are intended to be unique, but cannot always
be relied upon to unpredictable and unguessable, so should
not be relied upon for these purposes.
Examples
--------
SELECT UUID();
+--------------------------------------+
| UUID() |
+--------------------------------------+
| cd41294a-afb0-11df-bc9b-00241dd75637 |
+--------------------------------------+
URL: https://mariadb.com/kb/en/uuid/https://mariadb.com/kb/en/uuid/ � $ CHAR BYTEDescription
-----------
The CHAR BYTE data type is an alias for the
BINARY data type. This is a
compatibility feature.
URL: https://mariadb.com/kb/en/char-byte/https://mariadb.com/kb/en/char-byte/ # LONGBLOBSyntax
------
LONGBLOB
Description
-----------
A BLOB column with a
maximum length of 4,294,967,295 bytes or 4GB (232 - 1). The
effective maximum length of LONGBLOB columns depends on the
configured maximum packet size in the client/server protocol
and
available memory. Each LONGBLOB value is stored using a
four-byte
length prefix that indicates the number of bytes in the
value.
Oracle Mode
In Oracle mode from MariaDB 10.3, BLOB is a synonym for
LONGBLOB.
URL: https://mariadb.com/kb/en/longblob/https://mariadb.com/kb/en/longblob/ �# LONGTEXTSyntax
------
LONGTEXT [CHARACTER SET charset_name] [COLLATE
collation_name]
Description
-----------
A TEXT column with a maximum length of 4,294,967,295 or 4GB
(232 - 1) characters. The effective maximum length is less
if the value contains multi-byte characters. The effective
maximum length of LONGTEXT columns also depends on the
configured maximum packet size in the client/server protocol
and available memory. Each LONGTEXT value is stored using a
four-byte length prefix that indicates the number of bytes
in the value.
From MariaDB 10.2.7, JSON is an alias for LONGTEXT. See JSON
Data Type for details.
Oracle Mode
In Oracle mode from MariaDB 10.3, CLOB is a synonym for
LONGTEXT.
URL: https://mariadb.com/kb/en/longtext/https://mariadb.com/kb/en/longtext/ � !}:�� �� �.�UU �m � � ' RELEASE_LOCKSyntax
------
RELEASE_LOCK(str)
Description
-----------
Releases the lock named by the string str that was obtained
with GET_LOCK(). Returns 1 if the lock was released, 0 if
the lock was not established by this thread (in which case
the lock is not
released), and NULL if the named lock did not exist. The
lock does not exist if it was never obtained by a call to
GET_LOCK() or if it has previously been released.
MariaDB until 10.0.1
Before 10.0.2, GET_LOCK() released the existing lock, if
any. Since 10.0.2 this does not happen, because multiple
locks are allowed.
str is case insensitive. If str is an empty string or NULL,
RELEASE_LOCK() returns NULL and does nothing.
Statements using the RELEASE_LOCK() function are not safe
for replication.
The DO statement is convenient to use with RELEASE_LOCK().
Examples
--------
Connection1:
SELECT GET_LOCK('lock1',10);
+----------------------+
| GET_LOCK('lock1',10) |
+----------------------+
| 1 |
+----------------------+
Connection 2:
SELECT GET_LOCK('lock2',10);
+----------------------+
| GET_LOCK('lock2',10) |
+----------------------+
| 1 |
+----------------------+
Connection 1:
SELECT RELEASE_LOCK('lock1'), RELEASE_LOCK('lock2'),
RELEASE_LOCK('lock3');
+-----------------------+-----------------------+-----------------------+
| RELEASE_LOCK('lock1') | RELEASE_LOCK('lock2') |
RELEASE_LOCK('lock3') |
+-----------------------+-----------------------+-----------------------+
| 1 | 0 | NULL |
+-----------------------+-----------------------+-----------------------+
From MariaDB 10.0.2, it is possible to hold the same lock
recursively. This example is viewed using the
metadata_lock_info plugin:
SELECT GET_LOCK('lock3',10);
+----------------------+
| GET_LOCK('lock3',10) |
+----------------------+
| 1 |
+----------------------+
SELECT GET_LOCK('lock3',10);
+----------------------+
| GET_LOCK('lock3',10) |
+----------------------+
| 1 |
+----------------------+
SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO;
+-----------+---------------------+---------------+-----------+--------------+------------+
| THREAD_ID | LOCK_MODE | LOCK_DURATION | LOCK_TYPE |
TABLE_SCHEMA | TABLE_NAME |
+-----------+---------------------+---------------+-----------+--------------+------------+
| 46 | MDL_SHARED_NO_WRITE | NULL | User lock | lock3 | |
+-----------+---------------------+---------------+-----------+--------------+------------+
SELECT RELEASE_LOCK('lock3');
+-----------------------+
| RELEASE_LOCK('lock3') |
+-----------------------+
| 1 |
+-----------------------+
SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO;
+-----------+---------------------+---------------+-----------+--------------+------------+
| THREAD_ID | LOCK_MODE | LOCK_DURATION | LOCK_TYPE |
TABLE_SCHEMA | TABLE_NAME |
+-----------+---------------------+---------------+-----------+--------------+------------+
| 46 | MDL_SHARED_NO_WRITE | NULL | User lock | lock3 | |
+-----------+---------------------+---------------+-----------+--------------+------------+
SELECT RELEASE_LOCK('lock3');
+-----------------------+
| RELEASE_LOCK('lock3') |
+-----------------------+
| 1 |
+-----------------------+
SELECT * FROM INFORMATION_SCHEMA.METADATA_LOCK_INFO;
Empty set (0.000 sec)
URL: https://mariadb.com/kb/en/release_lock/https://mariadb.com/kb/en/release_lock/ � �' VALUES / VALUESyntax
------
VALUE(col_name)
MariaDB until 10.3.2
VALUES(col_name)
Description
-----------
In an INSERT ... ON DUPLICATE KEY UPDATE statement, you can
use the VALUES(col_name) function in the UPDATE clause to
refer to column values from the INSERT portion of the
statement. In other words, VALUES(col_name) in the UPDATE
clause refers to the value of col_name that would be
inserted, had no duplicate-key conflict occurred. This
function is especially useful in multiple-row inserts.
The VALUES() function is meaningful only in INSERT ... ON
DUPLICATE KEY UPDATE statements and returns NULL otherwise.
In MariaDB 10.3.3 this function was renamed to VALUE(),
because it's incompatible with the standard Table Value
Constructors syntax, implemented in MariaDB 10.3.3.
The VALUES() function can still be used even from MariaDB
10.3.3, but only in INSERT ... ON DUPLICATE KEY UPDATE
statements; it's a syntax error otherwise.
Examples
--------
INSERT INTO t (a,b,c) VALUES (1,2,3),(4,5,6)
ON DUPLICATE KEY UPDATE c=VALUE(a)+VALUE(b);
MariaDB until 10.3.2
INSERT INTO t (a,b,c) VALUES (1,2,3),(4,5,6)
ON DUPLICATE KEY UPDATE c=VALUES(a)+VALUES(b);
URL: https://mariadb.com/kb/en/values-value/https://mariadb.com/kb/en/values-value/ � � ||Syntax
------
OR, ||
Description
-----------
Logical OR. When both operands are non-NULL, the result is 1
if any
operand is non-zero, and 0 otherwise. With a NULL operand,
the result
is 1 if the other operand is non-zero, and NULL otherwise.
If both
operands are NULL, the result is NULL.
For this operator, short-circuit evaluation can be used.
Note that, if the PIPES_AS_CONCAT SQL_MODE is set, || is
used as a string concatenation operator. This means that a
|| b is the same as CONCAT(a,b). See CONCAT() for details.
Oracle Mode
In Oracle mode from MariaDB 10.3, || ignores NULL.
Examples
--------
SELECT 1 || 1;
+--------+
| 1 || 1 |
+--------+
| 1 |
+--------+
SELECT 1 || 0;
+--------+
| 1 || 0 |
+--------+
| 1 |
+--------+
SELECT 0 || 0;
+--------+
| 0 || 0 |
+--------+
| 0 |
+--------+
SELECT 0 || NULL;
+-----------+
| 0 || NULL |
+-----------+
| NULL |
+-----------+
SELECT 1 || NULL;
+-----------+
| 1 || NULL |
+-----------+
| 1 |
+-----------+
In Oracle mode, from MariaDB 10.3:
SELECT 0 || NULL;
+-----------+
| 0 || NULL |
+-----------+
| 0 |
+-----------+
URL: https://mariadb.com/kb/en/or/https://mariadb.com/kb/en/or/
% MEDIUMBLOBSyntax
------
MEDIUMBLOB
Description
-----------
A BLOB column with a maximum
length of 16,777,215 (224 - 1) bytes.
Each MEDIUMBLOB value is stored using a three-byte length
prefix that
indicates the number of bytes in the value.
URL: https://mariadb.com/kb/en/mediumblob/https://mariadb.com/kb/en/mediumblob/
�% MEDIUMTEXTSyntax
------
MEDIUMTEXT [CHARACTER SET charset_name] [COLLATE
collation_name]
Description
-----------
A TEXT column with a
maximum length of 16,777,215 (224 - 1)
characters. The effective maximum length is less if the
value
contains multi-byte characters. Each MEDIUMTEXT value is
stored using
a three-byte length prefix that indicates the number of
bytes in the
value.
URL: https://mariadb.com/kb/en/mediumtext/https://mariadb.com/kb/en/mediumtext/ 2 ROWThe ROW data type was introduced in MariaDB 10.3.0.
Syntax
------
ROW ( [{, }... ])
Description
-----------
ROW is a data type for stored procedure variables.
Features
ROW fields as normal variables
ROW fields (members) act as normal variables, and are able
to appear in all
query parts where a stored procedure variable is allowed:
Assignment is using the := operator and the SET command:
a.x:= 10;
a.x:= b.x;
SET a.x= 10, a.y=20, a.z= b.z;
Passing to functions and operators:
SELECT f1(rec.a), rec.a
URL: https://mariadb.com/kb/en/row/https://mariadb.com/kb/en/row/
�( SET Data TypeSyntax
------
SET('value1','value2',...) [CHARACTER SET charset_name]
[COLLATE collation_name]
Description
-----------
A set. A string object that can have zero or more values,
each of
which must be chosen from the list of values 'value1',
'value2', ... A
SET column can have a maximum of 64 members. SET values are
represented internally as integers.
URL: https://mariadb.com/kb/en/set-data-type/https://mariadb.com/kb/en/set-data-type/ � �:aW�VT�B
6
��+ �@ � �C Assignment Operator (=)Syntax
------
identifier = expr
Description
-----------
The equal sign is used as both an assignment operator in
certain contexts, and as a comparison operator. When used as
assignment operator, the value on the right is assigned to
the variable (or column, in some contexts) on the left.
Since its use can be ambiguous, unlike the := assignment
operator, the = assignment operator cannot be used in all
contexts, and is only valid as part of a SET statement, or
the SET clause of an UPDATE statement
This operator works with both user-defined variables and
local variables.
Examples
--------
UPDATE table_name SET x = 2 WHERE x > 100;
SET @x = 1, @y := 2;
URL:
https://mariadb.com/kb/en/assignment-operators-assignment-operator/https://mariadb.com/kb/en/assignment-operators-assignment-operator/ � � 5 Stored Aggregate FunctionsThe ability to create stored aggregate functions was added
in MariaDB 10.3.3.
Aggregate functions are functions that are computed over a
sequence of rows and return one result for the sequence of
rows.
Creating a custom aggregate function is done using the
CREATE FUNCTION statement with two main differences:
The addition of the AGGREGATE keyword, so CREATE AGGREGATE
FUNCTION
The FETCH GROUP NEXT ROW instruction inside the loop
Oracle PL/SQL compatibility using SQL/PL is provided
Standard Syntax
CREATE AGGREGATE FUNCTION function_name (parameters) RETURNS
return_type
BEGIN
All types of declarations
DECLARE CONTINUE HANDLER FOR NOT FOUND RETURN return_val;
LOOP
FETCH GROUP NEXT ROW; // fetches next row from table
other instructions
END LOOP;
END
Stored aggregate functions were a 2016 Google Summer of Code
project by Varun Gupta.
Using SQL/PL
SET sql_mode=Oracle;
DELIMITER //
CREATE AGGREGATE FUNCTION function_name (parameters) RETURN
return_type
declarations
BEGIN
LOOP
FETCH GROUP NEXT ROW; -- fetches next row from table
-- other instructions
END LOOP;
EXCEPTION
WHEN NO_DATA_FOUND THEN
RETURN return_val;
END //
DELIMITER ;
Examples
--------
First a simplified example:
CREATE TABLE marks(stud_id INT, grade_count INT);
INSERT INTO marks VALUES (1,6), (2,4), (3,7), (4,5), (5,8);
SELECT * FROM marks;
+---------+-------------+
| stud_id | grade_count |
+---------+-------------+
| 1 | 6 |
| 2 | 4 |
| 3 | 7 |
| 4 | 5 |
| 5 | 8 |
+---------+-------------+
DELIMITER //
CREATE AGGREGATE FUNCTION IF NOT EXISTS aggregate_count(x
INT) RETURNS INT
BEGIN
DECLARE count_students INT DEFAULT 0;
DECLARE CONTINUE HANDLER FOR NOT FOUND
RETURN count_students;
LOOP
FETCH GROUP NEXT ROW;
IF x THEN
SET count_students = count_students+1;
END IF;
END LOOP;
END //
DELIMITER ;
A non-trivial example that cannot easily be rewritten using
existing functions:
DELIMITER //
CREATE AGGREGATE FUNCTION medi_int(x INT) RETURNS DOUBLE
BEGIN
DECLARE CONTINUE HANDLER FOR NOT FOUND
BEGIN
DECLARE res DOUBLE;
DECLARE cnt INT DEFAULT (SELECT COUNT(*) FROM tt);
DECLARE lim INT DEFAULT (cnt-1) DIV 2;
IF cnt % 2 = 0 THEN
SET res = (SELECT AVG(a) FROM (SELECT a FROM tt ORDER BY a
LIMIT lim,2) ttt);
ELSE
SET res = (SELECT a FROM tt ORDER BY a LIMIT lim,1);
END IF;
DROP TEMPORARY TABLE tt;
RETURN res;
END;
CREATE TEMPORARY TABLE tt (a INT);
LOOP
FETCH GROUP NEXT ROW;
INSERT INTO tt VALUES (x);
END LOOP;
END //
DELIMITER ;
SQL/PL Example
This uses the same marks table as created above.
SET sql_mode=Oracle;
DELIMITER //
CREATE AGGREGATE FUNCTION aggregate_count(x INT) RETURN INT
AS count_students INT DEFAULT 0;
BEGIN
LOOP
FETCH GROUP NEXT ROW;
IF x THEN
SET count_students := count_students+1;
END IF;
END LOOP;
EXCEPTION
WHEN NO_DATA_FOUND THEN
RETURN count_students;
END aggregate_count //
DELIMITER ;
SELECT aggregate_count(stud_id) FROM marks;
URL: https://mariadb.com/kb/en/stored-aggregate-functions/https://mariadb.com/kb/en/stored-aggregate-functions/ � :
AVGSyntax
------
AVG([DISTINCT] expr)
Description
-----------
Returns the average value of expr. The DISTINCT option can
be used to return the average of the distinct values of
expr. NULL values are ignored. It is an aggregate function,
and so can be used with the GROUP BY clause.
AVG() returns NULL if there were no matching rows.
From MariaDB 10.2.0, AVG() can be used as a window function.
Examples
--------
CREATE TABLE sales (sales_value INT);
INSERT INTO sales VALUES(10),(20),(20),(40);
SELECT AVG(sales_value) FROM sales;
+------------------+
| AVG(sales_value) |
+------------------+
| 22.5000 |
+------------------+
SELECT AVG(DISTINCT(sales_value)) FROM sales;
+----------------------------+
| AVG(DISTINCT(sales_value)) |
+----------------------------+
| 23.3333 |
+----------------------------+
Commonly, AVG() is used with a GROUP BY clause:
CREATE TABLE student (name CHAR(10), test CHAR(10), score
TINYINT);
INSERT INTO student VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);
SELECT name, AVG(score) FROM student GROUP BY name;
+---------+------------+
| name | AVG(score) |
+---------+------------+
| Chun | 74.0000 |
| Esben | 37.0000 |
| Kaolin | 72.0000 |
| Tatiana | 85.0000 |
+---------+------------+
Be careful to avoid this common mistake, not grouping
correctly and returning mismatched data:
SELECT name,test,AVG(score) FROM student;
+------+------+------------+
| name | test | MIN(score) |
+------+------+------------+
| Chun | SQL | 31 |
+------+------+------------+
As a window function:
CREATE TABLE student_test (name CHAR(10), test CHAR(10),
score TINYINT);
INSERT INTO student_test VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);
SELECT name, test, score, AVG(score) OVER (PARTITION BY
test)
AS average_by_test FROM student_test;
+---------+--------+-------+-----------------+
| name | test | score | average_by_test |
+---------+--------+-------+-----------------+
| Chun | SQL | 75 | 65.2500 |
| Chun | Tuning | 73 | 68.7500 |
| Esben | SQL | 43 | 65.2500 |
| Esben | Tuning | 31 | 68.7500 |
| Kaolin | SQL | 56 | 65.2500 |
| Kaolin | Tuning | 88 | 68.7500 |
| Tatiana | SQL | 87 | 65.2500 |
| Tatiana | Tuning | 83 | 68.7500 |
+---------+--------+-------+-----------------+
URL: https://mariadb.com/kb/en/avg/https://mariadb.com/kb/en/avg/ % F $ TIMESTAMPSyntax
------
TIMESTAMP [(
URL: https://mariadb.com/kb/en/timestamp/https://mariadb.com/kb/en/timestamp/ & # TINYBLOBSyntax
------
TINYBLOB
Description
-----------
A BLOB column with a maximum length of
255 (28 - 1) bytes. Each
TINYBLOB value is stored using a one-byte length prefix that
indicates
the number of bytes in the value.
URL: https://mariadb.com/kb/en/tinyblob/https://mariadb.com/kb/en/tinyblob/ ( �# TINYTEXTSyntax
------
TINYTEXT [CHARACTER SET charset_name] [COLLATE
collation_name]
Description
-----------
A TEXT column with a maximum length of 255 (28 - 1)
characters. The effective maximum length is less if the
value contains multi-byte characters. Each TINYTEXT value is
stored using a one-byte length prefix that indicates the
number of bytes in the value.
URL: https://mariadb.com/kb/en/tinytext/https://mariadb.com/kb/en/tinytext/ ���B� �i
n< b��" �� � �" BIT_ANDSyntax
------
BIT_AND(expr)
Description
-----------
Returns the bitwise AND of all bits in expr. The calculation
is performed with 64-bit (BIGINT) precision. It is an
aggregate function, and so can be used with the GROUP BY
clause.
From MariaDB 10.2.0, BIT_AND() can be used as a window
function.
Examples
--------
CREATE TABLE vals (x INT);
INSERT INTO vals VALUES(111),(110),(100);
SELECT BIT_AND(x), BIT_OR(x), BIT_XOR(x) FROM vals;
+------------+-----------+------------+
| BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+------------+-----------+------------+
| 100 | 111 | 101 |
+------------+-----------+------------+
As an aggregate function:
CREATE TABLE vals2 (category VARCHAR(1), x INT);
INSERT INTO vals2 VALUES
('a',111),('a',110),('a',100),
('b','000'),('b',001),('b',011);
SELECT category, BIT_AND(x), BIT_OR(x), BIT_XOR(x)
FROM vals GROUP BY category;
+----------+------------+-----------+------------+
| category | BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+----------+------------+-----------+------------+
| a | 100 | 111 | 101 |
| b | 0 | 11 | 10 |
+----------+------------+-----------+------------+
URL: https://mariadb.com/kb/en/bit_and/https://mariadb.com/kb/en/bit_and/ � �! BIT_ORSyntax
------
BIT_OR(expr)
Description
-----------
Returns the bitwise OR of all bits in expr. The calculation
is performed with 64-bit (BIGINT) precision. It is an
aggregate function, and so can be used with the GROUP BY
clause.
From MariaDB 10.2.0, BIT_OR can be used as a window
function.
Examples
--------
CREATE TABLE vals (x INT);
INSERT INTO vals VALUES(111),(110),(100);
SELECT BIT_AND(x), BIT_OR(x), BIT_XOR(x) FROM vals;
+------------+-----------+------------+
| BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+------------+-----------+------------+
| 100 | 111 | 101 |
+------------+-----------+------------+
As an aggregate function:
CREATE TABLE vals2 (category VARCHAR(1), x INT);
INSERT INTO vals2 VALUES
('a',111),('a',110),('a',100),
('b','000'),('b',001),('b',011);
SELECT category, BIT_AND(x), BIT_OR(x), BIT_XOR(x)
FROM vals GROUP BY category;
+----------+------------+-----------+------------+
| category | BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+----------+------------+-----------+------------+
| a | 100 | 111 | 101 |
| b | 0 | 11 | 10 |
+----------+------------+-----------+------------+
URL: https://mariadb.com/kb/en/bit_or/https://mariadb.com/kb/en/bit_or/ � �" BIT_XORSyntax
------
BIT_XOR(expr)
Description
-----------
Returns the bitwise XOR of all bits in expr. The calculation
is performed with 64-bit (BIGINT) precision. It is an
aggregate function, and so can be used with the GROUP BY
clause.
From MariaDB 10.2.0, BIT_XOR() can be used as a window
function.
Examples
--------
CREATE TABLE vals (x INT);
INSERT INTO vals VALUES(111),(110),(100);
SELECT BIT_AND(x), BIT_OR(x), BIT_XOR(x) FROM vals;
+------------+-----------+------------+
| BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+------------+-----------+------------+
| 100 | 111 | 101 |
+------------+-----------+------------+
As an aggregate function:
CREATE TABLE vals2 (category VARCHAR(1), x INT);
INSERT INTO vals2 VALUES
('a',111),('a',110),('a',100),
('b','000'),('b',001),('b',011);
SELECT category, BIT_AND(x), BIT_OR(x), BIT_XOR(x)
FROM vals GROUP BY category;
+----------+------------+-----------+------------+
| category | BIT_AND(x) | BIT_OR(x) | BIT_XOR(x) |
+----------+------------+-----------+------------+
| a | 100 | 111 | 101 |
| b | 0 | 11 | 10 |
+----------+------------+-----------+------------+
URL: https://mariadb.com/kb/en/bit_xor/https://mariadb.com/kb/en/bit_xor/ � @ COUNTSyntax
------
COUNT(expr)
Description
-----------
Returns a count of the number of non-NULL values of expr in
the rows retrieved by a SELECT statement. The result is a
BIGINT value. It is an aggregate function, and so can be
used with the GROUP BY clause.
COUNT(*) counts the total number of rows in a table.
COUNT() returns 0 if there were no matching rows.
From MariaDB 10.2.0, COUNT() can be used as a window
function.
Examples
--------
CREATE TABLE student (name CHAR(10), test CHAR(10), score
TINYINT);
INSERT INTO student VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);
SELECT COUNT(*) FROM student;
+----------+
| COUNT(*) |
+----------+
| 8 |
+----------+
COUNT(DISTINCT) example:
SELECT COUNT(DISTINCT (name)) FROM student;
+------------------------+
| COUNT(DISTINCT (name)) |
+------------------------+
| 4 |
+------------------------+
As a window function
CREATE OR REPLACE TABLE student_test (name CHAR(10), test
CHAR(10), score TINYINT);
INSERT INTO student_test VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87);
SELECT name, test, score, COUNT(score) OVER (PARTITION BY
name)
AS tests_written FROM student_test;
+---------+--------+-------+---------------+
| name | test | score | tests_written |
+---------+--------+-------+---------------+
| Chun | SQL | 75 | 2 |
| Chun | Tuning | 73 | 2 |
| Esben | SQL | 43 | 2 |
| Esben | Tuning | 31 | 2 |
| Kaolin | SQL | 56 | 2 |
| Kaolin | Tuning | 88 | 2 |
| Tatiana | SQL | 87 | 1 |
+---------+--------+-------+---------------+
URL: https://mariadb.com/kb/en/count/https://mariadb.com/kb/en/count/ . p CLOSESyntax
------
CLOSE cursor_name
Description
-----------
This statement closes a previously opened cursor. The cursor
must have been previously opened or else an error occurs.
If not closed explicitly, a cursor is closed at the end of
the
compound statement in which it was declared.
See Cursor Overview for an example.
URL: https://mariadb.com/kb/en/close/https://mariadb.com/kb/en/close/ 0 ? ) DECLARE CURSORSyntax
------
URL: https://mariadb.com/kb/en/declare-cursor/https://mariadb.com/kb/en/declare-cursor/ 3 FETCHSyntax
------
FETCH cursor_name INTO var_name [, var_name] ...
Description
-----------
This statement fetches the next row (if a row exists) using
the
specified open cursor, and advances the cursor pointer.
var_name can be a local variable, but not a user-defined
variable.
If no more rows are available, a No Data condition occurs
with
SQLSTATE value 02000. To detect this condition, you can set
up a
handler for it (or for a NOT FOUND condition).
See Cursor Overview for an example.
URL: https://mariadb.com/kb/en/fetch/https://mariadb.com/kb/en/fetch/ 5 p GOTOThe GOTO statement was introduced in MariaDB 10.3 for Oracle
compatibility.
Syntax
------
GOTO label
Description
-----------
The GOTO statement causes the code to jump to the specified
label, and continue operating from there. It is only
accepted when in Oracle mode.
Example
SET sql_mode=ORACLE;
DELIMITER //
CREATE OR REPLACE PROCEDURE p1 AS
BEGIN
SELECT 1;
GOTO label;
SELECT 2;
SELECT 3;
END;
//
DELIMITER
call p1();
+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.000 sec)
+---+
| 3 |
+---+
| 3 |
+---+
1 row in set (0.000 sec)
URL: https://mariadb.com/kb/en/goto/https://mariadb.com/kb/en/goto/ b�K�� ��}s� ��� �p$9$ �\ � ? MAXSyntax
------
MAX([DISTINCT] expr)
Description
-----------
Returns the largest, or maximum, value of expr. MAX() can
also take a string
argument in which case it returns the maximum string value.
The DISTINCT
keyword can be used to find the maximum of the distinct
values of expr,
however, this produces the same result as omitting DISTINCT.
Note that SET and ENUM fields are currently compared by
their string value rather than their relative position in
the set, so MAX() may produce a different highest result
than ORDER BY DESC.
It is an aggregate function, and so can be used with the
GROUP BY clause.
From MariaDB 10.2.2, MAX() can be used as a window function.
MAX() returns NULL if there were no matching rows.
Examples
--------
CREATE TABLE student (name CHAR(10), test CHAR(10), score
TINYINT);
INSERT INTO student VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);
SELECT name, MAX(score) FROM student GROUP BY name;
+---------+------------+
| name | MAX(score) |
+---------+------------+
| Chun | 75 |
| Esben | 43 |
| Kaolin | 88 |
| Tatiana | 87 |
+---------+------------+
MAX string:
SELECT MAX(name) FROM student;
+-----------+
| MAX(name) |
+-----------+
| Tatiana |
+-----------+
Be careful to avoid this common mistake, not grouping
correctly and returning mismatched data:
SELECT name,test,MAX(SCORE) FROM student;
+------+------+------------+
| name | test | MAX(SCORE) |
+------+------+------------+
| Chun | SQL | 88 |
+------+------+------------+
Difference between ORDER BY DESC and MAX():
CREATE TABLE student2(name CHAR(10),grade
ENUM('b','c','a'));
INSERT INTO student2
VALUES('Chun','b'),('Esben','c'),('Kaolin','a');
SELECT MAX(grade) FROM student2;
+------------+
| MAX(grade) |
+------------+
| c |
+------------+
SELECT grade FROM student2 ORDER BY grade DESC LIMIT 1;
+-------+
| grade |
+-------+
| a |
+-------+
As a window function:
CREATE OR REPLACE TABLE student_test (name CHAR(10), test
CHAR(10), score TINYINT);
INSERT INTO student_test VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87);
SELECT name, test, score, MAX(score)
OVER (PARTITION BY name) AS highest_score FROM
student_test;
+---------+--------+-------+---------------+
| name | test | score | highest_score |
+---------+--------+-------+---------------+
| Chun | SQL | 75 | 75 |
| Chun | Tuning | 73 | 75 |
| Esben | SQL | 43 | 43 |
| Esben | Tuning | 31 | 43 |
| Kaolin | SQL | 56 | 88 |
| Kaolin | Tuning | 88 | 88 |
| Tatiana | SQL | 87 | 87 |
+---------+--------+-------+---------------+
URL: https://mariadb.com/kb/en/max/https://mariadb.com/kb/en/max/ � + MINSyntax
------
MIN([DISTINCT] expr)
Description
-----------
Returns the minimum value of expr. MIN() may take a string
argument, in which case it returns the minimum string value.
The DISTINCT
keyword can be used to find the minimum of the distinct
values of expr,
however, this produces the same result as omitting DISTINCT.
Note that SET and ENUM fields are currently compared by
their string value rather than their relative position in
the set, so MIN() may produce a different lowest result than
ORDER BY ASC.
It is an aggregate function, and so can be used with the
GROUP BY clause.
From MariaDB 10.2.2, MIN() can be used as a window function.
MIN() returns NULL if there were no matching rows.
Examples
--------
CREATE TABLE student (name CHAR(10), test CHAR(10), score
TINYINT);
INSERT INTO student VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);
SELECT name, MIN(score) FROM student GROUP BY name;
+---------+------------+
| name | MIN(score) |
+---------+------------+
| Chun | 73 |
| Esben | 31 |
| Kaolin | 56 |
| Tatiana | 83 |
+---------+------------+
MIN() with a string:
SELECT MIN(name) FROM student;
+-----------+
| MIN(name) |
+-----------+
| Chun |
+-----------+
Be careful to avoid this common mistake, not grouping
correctly and returning mismatched data:
SELECT name,test,MIN(score) FROM student;
+------+------+------------+
| name | test | MIN(score) |
+------+------+------------+
| Chun | SQL | 31 |
+------+------+------------+
Difference between ORDER BY ASC and MIN():
CREATE TABLE student2(name CHAR(10),grade
ENUM('b','c','a'));
INSERT INTO student2
VALUES('Chun','b'),('Esben','c'),('Kaolin','a');
SELECT MIN(grade) FROM student2;
+------------+
| MIN(grade) |
+------------+
| a |
+------------+
SELECT grade FROM student2 ORDER BY grade ASC LIMIT 1;
+-------+
| grade |
+-------+
| b |
+-------+
As a window function:
CREATE OR REPLACE TABLE student_test (name CHAR(10), test
CHAR(10), score TINYINT);
INSERT INTO student_test VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87);
SELECT name, test, score, MIN(score)
OVER (PARTITION BY name) AS lowest_score FROM student_test;
+---------+--------+-------+--------------+
| name | test | score | lowest_score |
+---------+--------+-------+--------------+
| Chun | SQL | 75 | 73 |
| Chun | Tuning | 73 | 73 |
| Esben | SQL | 43 | 31 |
| Esben | Tuning | 31 | 31 |
| Kaolin | SQL | 56 | 56 |
| Kaolin | Tuning | 88 | 56 |
| Tatiana | SQL | 87 | 87 |
+---------+--------+-------+--------------+
URL: https://mariadb.com/kb/en/min/https://mariadb.com/kb/en/min/ 6 � IFSyntax
------
IF search_condition THEN statement_list
[ELSEIF search_condition THEN statement_list] ...
[ELSE statement_list]
END IF;
Description
-----------
IF implements a basic conditional construct. If the
search_condition
evaluates to true, the corresponding SQL statement list is
executed.
If no search_condition matches, the statement list in the
ELSE clause
is executed. Each statement_list consists of one or more
statements.
URL: https://mariadb.com/kb/en/if/https://mariadb.com/kb/en/if/ 7 �" ITERATESyntax
------
ITERATE label
ITERATE can appear only within LOOP, REPEAT, and WHILE
statements.
ITERATE means "do the loop again", and uses the
statement's label to determine which statements to repeat.
The label must be in the same stored program, not in a
caller procedure.
If you try to use ITERATE with a non-existing label, or if
the label is associated to a construct which is not a loop,
the following error will be produced:
ERROR 1308 (42000): ITERATE with no matching label:
Below is an example of how ITERATE might be used:
CREATE PROCEDURE doiterate(p1 INT)
BEGIN
label1: LOOP
SET p1 = p1 + 1;
IF p1
URL: https://mariadb.com/kb/en/iterate/https://mariadb.com/kb/en/iterate/ : � LOOPSyntax
------
[begin_label:] LOOP
statement_list
END LOOP [end_label]
Description
-----------
LOOP implements a simple loop construct, enabling repeated
execution
of the statement list, which consists of one or more
statements, each
terminated by a semicolon (i.e., ;) statement delimiter. The
statements
within the loop are repeated until the loop is exited;
usually this is
accomplished with a LEAVE statement.
A LOOP statement can be labeled. end_label cannot be given
unless
begin_label also is present. If both are present, they must
be the
same.
See Delimiters in the mysql client for more on delimiter
usage in the client.
URL: https://mariadb.com/kb/en/loop/https://mariadb.com/kb/en/loop/ ����� z Z n �*� �� � ` STDSyntax
------
STD(expr)
Description
-----------
Returns the population standard deviation of expr. This is
an extension
to standard SQL. The standard SQL function STDDEV_POP() can
be used instead.
It is an aggregate function, and so can be used with the
GROUP BY clause.
From MariaDB 10.2.2, STD() can be used as a window function.
This function returns NULL if there were no matching rows.
Examples
--------
As an aggregate function:
CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);
INSERT INTO stats VALUES
('a',1),('a',2),('a',3),
('b',11),('b',12),('b',20),('b',30),('b',60);
SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x)
FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a | 0.8165 | 1.0000 | 0.6667 |
| b | 18.0400 | 20.1693 | 325.4400 |
+----------+---------------+----------------+------------+
As a window function:
CREATE OR REPLACE TABLE student_test (name CHAR(10), test
CHAR(10), score TINYINT);
INSERT INTO student_test VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87);
SELECT name, test, score, STDDEV_POP(score)
OVER (PARTITION BY test) AS stddev_results FROM
student_test;
+---------+--------+-------+----------------+
| name | test | score | stddev_results |
+---------+--------+-------+----------------+
| Chun | SQL | 75 | 16.9466 |
| Chun | Tuning | 73 | 24.1247 |
| Esben | SQL | 43 | 16.9466 |
| Esben | Tuning | 31 | 24.1247 |
| Kaolin | SQL | 56 | 16.9466 |
| Kaolin | Tuning | 88 | 24.1247 |
| Tatiana | SQL | 87 | 16.9466 |
+---------+--------+-------+----------------+
URL: https://mariadb.com/kb/en/std/https://mariadb.com/kb/en/std/ � {! STDDEVSyntax
------
STDDEV(expr)
Description
-----------
Returns the population standard deviation of expr. This
function is
provided for compatibility with Oracle. The standard SQL
function
STDDEV_POP() can be used instead.
It is an aggregate function, and so can be used with the
GROUP BY clause.
From MariaDB 10.2.2, STDDEV() can be used as a window
function.
This function returns NULL if there were no matching rows.
Examples
--------
As an aggregate function:
CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);
INSERT INTO stats VALUES
('a',1),('a',2),('a',3),
('b',11),('b',12),('b',20),('b',30),('b',60);
SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x)
FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a | 0.8165 | 1.0000 | 0.6667 |
| b | 18.0400 | 20.1693 | 325.4400 |
+----------+---------------+----------------+------------+
As a window function:
CREATE OR REPLACE TABLE student_test (name CHAR(10), test
CHAR(10), score TINYINT);
INSERT INTO student_test VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87);
SELECT name, test, score, STDDEV_POP(score)
OVER (PARTITION BY test) AS stddev_results FROM
student_test;
+---------+--------+-------+----------------+
| name | test | score | stddev_results |
+---------+--------+-------+----------------+
| Chun | SQL | 75 | 16.9466 |
| Chun | Tuning | 73 | 24.1247 |
| Esben | SQL | 43 | 16.9466 |
| Esben | Tuning | 31 | 24.1247 |
| Kaolin | SQL | 56 | 16.9466 |
| Kaolin | Tuning | 88 | 24.1247 |
| Tatiana | SQL | 87 | 16.9466 |
+---------+--------+-------+----------------+
URL: https://mariadb.com/kb/en/stddev/https://mariadb.com/kb/en/stddev/ �
% STDDEV_POPSyntax
------
STDDEV_POP(expr)
Description
-----------
Returns the population standard deviation of expr (the
square root of
VAR_POP()). You can also use STD() or
STDDEV(), which are equivalent but not standard SQL.
It is an aggregate function, and so can be used with the
GROUP BY clause.
From MariaDB 10.2.2, STDDEV_POP() can be used as a window
function.
STDDEV_POP() returns NULL if there were no matching rows.
Examples
--------
As an aggregate function:
CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);
INSERT INTO stats VALUES
('a',1),('a',2),('a',3),
('b',11),('b',12),('b',20),('b',30),('b',60);
SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x)
FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a | 0.8165 | 1.0000 | 0.6667 |
| b | 18.0400 | 20.1693 | 325.4400 |
+----------+---------------+----------------+------------+
As a window function:
CREATE OR REPLACE TABLE student_test (name CHAR(10), test
CHAR(10), score TINYINT);
INSERT INTO student_test VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87);
SELECT name, test, score, STDDEV_POP(score)
OVER (PARTITION BY test) AS stddev_results FROM
student_test;
+---------+--------+-------+----------------+
| name | test | score | stddev_results |
+---------+--------+-------+----------------+
| Chun | SQL | 75 | 16.9466 |
| Chun | Tuning | 73 | 24.1247 |
| Esben | SQL | 43 | 16.9466 |
| Esben | Tuning | 31 | 24.1247 |
| Kaolin | SQL | 56 | 16.9466 |
| Kaolin | Tuning | 88 | 24.1247 |
| Tatiana | SQL | 87 | 16.9466 |
+---------+--------+-------+----------------+
URL: https://mariadb.com/kb/en/stddev_pop/https://mariadb.com/kb/en/stddev_pop/ ; 5 OPENSyntax
------
URL: https://mariadb.com/kb/en/open/https://mariadb.com/kb/en/open/ > �! RETURNSyntax
------
RETURN expr
The RETURN statement terminates execution of a stored
function and
returns the value expr to the function caller. There must be
at least
one RETURN statement in a stored function. If the function
has multiple exit points, all exit points must have a
RETURN.
This statement is not used in stored procedures, triggers,
or events. LEAVE can be used instead.
The following example shows that RETURN can return the
result of a scalar subquery:
CREATE FUNCTION users_count() RETURNS BOOL
READS SQL DATA
BEGIN
RETURN (SELECT COUNT(DISTINCT User) FROM mysql.user);
END;
URL: https://mariadb.com/kb/en/return/https://mariadb.com/kb/en/return/ A � WHILESyntax
------
[begin_label:] WHILE search_condition DO
statement_list
END WHILE [end_label]
Description
-----------
The statement list within a WHILE statement is repeated as
long as the
search_condition is true. statement_list consists of one or
more
statements. If the loop must be executed at least once,
REPEAT ... LOOP can be used instead.
A WHILE statement can be labeled. end_label cannot be given
unless
begin_label also is present. If both are present, they must
be the
same.
Examples
--------
CREATE PROCEDURE dowhile()
BEGIN
DECLARE v1 INT DEFAULT 5;
WHILE v1 > 0 DO
...
SET v1 = v1 - 1;
END WHILE;
END
URL: https://mariadb.com/kb/en/while/https://mariadb.com/kb/en/while/ 4�m�f K��� �u��� � � r SUMSyntax
------
SUM([DISTINCT] expr)
Description
-----------
Returns the sum of expr. If the return set has no rows,
SUM() returns
NULL. The DISTINCT keyword can be used to sum only the
distinct values
of expr.
From MariaDB 10.2.0, SUM() can be used as a window function,
although not with the DISTINCT specifier.
Examples
--------
CREATE TABLE sales (sales_value INT);
INSERT INTO sales VALUES(10),(20),(20),(40);
SELECT SUM(sales_value) FROM sales;
+------------------+
| SUM(sales_value) |
+------------------+
| 90 |
+------------------+
SELECT SUM(DISTINCT(sales_value)) FROM sales;
+----------------------------+
| SUM(DISTINCT(sales_value)) |
+----------------------------+
| 70 |
+----------------------------+
Commonly, SUM is used with a GROUP BY clause:
CREATE TABLE sales (name CHAR(10), month CHAR(10), units
INT);
INSERT INTO sales VALUES
('Chun', 'Jan', 75), ('Chun', 'Feb', 73),
('Esben', 'Jan', 43), ('Esben', 'Feb', 31),
('Kaolin', 'Jan', 56), ('Kaolin', 'Feb', 88),
('Tatiana', 'Jan', 87), ('Tatiana', 'Feb', 83);
SELECT name, SUM(units) FROM sales GROUP BY name;
+---------+------------+
| name | SUM(units) |
+---------+------------+
| Chun | 148 |
| Esben | 74 |
| Kaolin | 144 |
| Tatiana | 170 |
+---------+------------+
The GROUP BY clause is required when using an aggregate
function along with regular column data, otherwise the
result will be a mismatch, as in the following common type
of mistake:
SELECT name,SUM(units) FROM sales
;
+------+------------+
| name | SUM(units) |
+------+------------+
| Chun | 536 |
+------+------------+
As a window function:
CREATE OR REPLACE TABLE student_test (name CHAR(10), test
CHAR(10), score TINYINT);
INSERT INTO student_test VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87);
SELECT name, test, score, SUM(score) OVER (PARTITION BY
name) AS total_score FROM student_test;
+---------+--------+-------+-------------+
| name | test | score | total_score |
+---------+--------+-------+-------------+
| Chun | SQL | 75 | 148 |
| Chun | Tuning | 73 | 148 |
| Esben | SQL | 43 | 74 |
| Esben | Tuning | 31 | 74 |
| Kaolin | SQL | 56 | 144 |
| Kaolin | Tuning | 88 | 144 |
| Tatiana | SQL | 87 | 87 |
+---------+--------+-------+-------------+
URL: https://mariadb.com/kb/en/sum/https://mariadb.com/kb/en/sum/ � [ # VARIANCESyntax
------
VARIANCE(expr)
Description
-----------
Returns the population standard variance of expr. This is an
extension to
standard SQL. The standard SQL function VAR_POP() can be
used
instead.
Variance is calculated by
working out the mean for the set
for each number, subtracting the mean and squaring the
result
calculate the average of the resulting differences
It is an aggregate function, and so can be used with the
GROUP BY clause.
From MariaDB 10.2.2, VARIANCE() can be used as a window
function.
VARIANCE() returns NULL if there were no matching rows.
Examples
--------
CREATE TABLE v(i tinyint);
INSERT INTO v VALUES(101),(99);
SELECT VARIANCE(i) FROM v;
+-------------+
| VARIANCE(i) |
+-------------+
| 1.0000 |
+-------------+
INSERT INTO v VALUES(120),(80);
SELECT VARIANCE(i) FROM v;
+-------------+
| VARIANCE(i) |
+-------------+
| 200.5000 |
+-------------+
As an aggregate function:
CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);
INSERT INTO stats VALUES
('a',1),('a',2),('a',3),
('b',11),('b',12),('b',20),('b',30),('b',60);
SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x)
FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a | 0.8165 | 1.0000 | 0.6667 |
| b | 18.0400 | 20.1693 | 325.4400 |
+----------+---------------+----------------+------------+
As a window function:
CREATE OR REPLACE TABLE student_test (name CHAR(10), test
CHAR(10), score TINYINT);
INSERT INTO student_test VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87);
SELECT name, test, score, VAR_POP(score)
OVER (PARTITION BY test) AS variance_results FROM
student_test;
+---------+--------+-------+------------------+
| name | test | score | variance_results |
+---------+--------+-------+------------------+
| Chun | SQL | 75 | 287.1875 |
| Chun | Tuning | 73 | 582.0000 |
| Esben | SQL | 43 | 287.1875 |
| Esben | Tuning | 31 | 582.0000 |
| Kaolin | SQL | 56 | 287.1875 |
| Kaolin | Tuning | 88 | 582.0000 |
| Tatiana | SQL | 87 | 287.1875 |
+---------+--------+-------+------------------+
URL: https://mariadb.com/kb/en/variance/https://mariadb.com/kb/en/variance/ B Q ! BUFFERA synonym for ST_BUFFER.
URL: https://mariadb.com/kb/en/buffer/https://mariadb.com/kb/en/buffer/ C
Y % CONVEXHULLA synonym for ST_CONVEXHULL.
URL: https://mariadb.com/kb/en/convexhull/https://mariadb.com/kb/en/convexhull/ D �- GEOMETRYCOLLECTIONSyntax
------
GeometryCollection(g1,g2,...)
Description
-----------
Constructs a WKB GeometryCollection. If any argument is not
a well-formed WKB representation of a geometry, the return
value is NULL.
Examples
--------
CREATE TABLE gis_geometrycollection (g GEOMETRYCOLLECTION);
SHOW FIELDS FROM gis_geometrycollection;
INSERT INTO gis_geometrycollection VALUES
(GeomCollFromText('GEOMETRYCOLLECTION(POINT(0 0),
LINESTRING(0 0,10 10))')),
(GeometryFromWKB(AsWKB(GeometryCollection(Point(44, 6),
LineString(Point(3, 6), Point(7, 9)))))),
(GeomFromText('GeometryCollection()')),
(GeomFromText('GeometryCollection EMPTY'));
URL: https://mariadb.com/kb/en/geometrycollection/https://mariadb.com/kb/en/geometrycollection/ F �* MULTILINESTRINGSyntax
------
MultiLineString(ls1,ls2,...)
Description
-----------
Constructs a WKB MultiLineString value using WKB LineString
arguments. If any argument is not a WKB LineString, the
return value is
NULL.
Example
CREATE TABLE gis_multi_line (g MULTILINESTRING);
INSERT INTO gis_multi_line VALUES
(MultiLineStringFromText('MULTILINESTRING((10 48,10 21,10
0),(16 0,16 23,16 48))')),
(MLineFromText('MULTILINESTRING((10 48,10 21,10 0))')),
(MLineFromWKB(AsWKB(MultiLineString(LineString(Point(1, 2),
Point(3, 5)), LineString(Point(2, 5),Point(5, 8),Point(21,
7))))));
URL: https://mariadb.com/kb/en/multilinestring/https://mariadb.com/kb/en/multilinestring/ G
p% MULTIPOINTSyntax
------
MultiPoint(pt1,pt2,...)
Description
-----------
Constructs a WKB MultiPoint value using WKB Point arguments.
If any argument is not a WKB Point, the return value is
NULL.
Examples
--------
SET @g = ST_GEOMFROMTEXT('MultiPoint( 1 1, 2 2, 5 3, 7 2, 9
3, 8 4, 6 6, 6 9, 4 9, 1 5 )');
CREATE TABLE gis_multi_point (g MULTIPOINT);
INSERT INTO gis_multi_point VALUES
(MultiPointFromText('MULTIPOINT(0 0,10 10,10 20,20
20)')),
(MPointFromText('MULTIPOINT(1 1,11 11,11 21,21 21)')),
(MPointFromWKB(AsWKB(MultiPoint(Point(3, 6), Point(4,
10)))));
URL: https://mariadb.com/kb/en/multipoint/https://mariadb.com/kb/en/multipoint/ 1�i�] �� A� � � � b� �� � � " VAR_POPSyntax
------
VAR_POP(expr)
Description
-----------
Returns the population standard variance of expr. It
considers rows as
the whole population, not as a sample, so it has the number
of rows as
the denominator. You can also use VARIANCE(), which is
equivalent but
is not standard SQL.
Variance is calculated by
working out the mean for the set
for each number, subtracting the mean and squaring the
result
calculate the average of the resulting differences
It is an aggregate function, and so can be used with the
GROUP BY clause.
From MariaDB 10.2.2, VAR_POP() can be used as a window
function.
VAR_POP() returns NULL if there were no matching rows.
Examples
--------
CREATE TABLE v(i tinyint);
INSERT INTO v VALUES(101),(99);
SELECT VAR_POP(i) FROM v;
+------------+
| VAR_POP(i) |
+------------+
| 1.0000 |
+------------+
INSERT INTO v VALUES(120),(80);
SELECT VAR_POP(i) FROM v;
+------------+
| VAR_POP(i) |
+------------+
| 200.5000 |
+------------+
As an aggregate function:
CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);
INSERT INTO stats VALUES
('a',1),('a',2),('a',3),
('b',11),('b',12),('b',20),('b',30),('b',60);
SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x)
FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a | 0.8165 | 1.0000 | 0.6667 |
| b | 18.0400 | 20.1693 | 325.4400 |
+----------+---------------+----------------+------------+
As a window function:
CREATE OR REPLACE TABLE student_test (name CHAR(10), test
CHAR(10), score TINYINT);
INSERT INTO student_test VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87);
SELECT name, test, score, VAR_POP(score)
OVER (PARTITION BY test) AS variance_results FROM
student_test;
+---------+--------+-------+------------------+
| name | test | score | variance_results |
+---------+--------+-------+------------------+
| Chun | SQL | 75 | 287.1875 |
| Chun | Tuning | 73 | 582.0000 |
| Esben | SQL | 43 | 287.1875 |
| Esben | Tuning | 31 | 582.0000 |
| Kaolin | SQL | 56 | 287.1875 |
| Kaolin | Tuning | 88 | 582.0000 |
| Tatiana | SQL | 87 | 287.1875 |
+---------+--------+-------+------------------+
URL: https://mariadb.com/kb/en/var_pop/https://mariadb.com/kb/en/var_pop/ � D# VAR_SAMPSyntax
------
VAR_SAMP(expr)
Description
-----------
Returns the sample variance of expr. That is, the
denominator is the number of rows minus one.
It is an aggregate function, and so can be used with the
GROUP BY clause.
From MariaDB 10.2.2, VAR_SAMP() can be used as a window
function.
VAR_SAMP() returns NULL if there were no matching rows.
Examples
--------
As an aggregate function:
CREATE OR REPLACE TABLE stats (category VARCHAR(2), x INT);
INSERT INTO stats VALUES
('a',1),('a',2),('a',3),
('b',11),('b',12),('b',20),('b',30),('b',60);
SELECT category, STDDEV_POP(x), STDDEV_SAMP(x), VAR_POP(x)
FROM stats GROUP BY category;
+----------+---------------+----------------+------------+
| category | STDDEV_POP(x) | STDDEV_SAMP(x) | VAR_POP(x) |
+----------+---------------+----------------+------------+
| a | 0.8165 | 1.0000 | 0.6667 |
| b | 18.0400 | 20.1693 | 325.4400 |
+----------+---------------+----------------+------------+
As a window function:
CREATE OR REPLACE TABLE student_test (name CHAR(10), test
CHAR(10), score TINYINT);
INSERT INTO student_test VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87);
SELECT name, test, score, VAR_SAMP(score)
OVER (PARTITION BY test) AS variance_results FROM
student_test;
+---------+--------+-------+------------------+
| name | test | score | variance_results |
+---------+--------+-------+------------------+
| Chun | SQL | 75 | 382.9167 |
| Chun | Tuning | 73 | 873.0000 |
| Esben | SQL | 43 | 382.9167 |
| Esben | Tuning | 31 | 873.0000 |
| Kaolin | SQL | 56 | 382.9167 |
| Kaolin | Tuning | 88 | 873.0000 |
| Tatiana | SQL | 87 | 382.9167 |
+---------+--------+-------+------------------+
URL: https://mariadb.com/kb/en/var_samp/https://mariadb.com/kb/en/var_samp/ � " CHARSETSyntax
------
CHARSET(str)
Description
-----------
Returns the character set of the string argument. If str is
not a string, it is considered as a binary string (so the
function returns 'binary'). This applies to NULL, too. The
return value is a string in the utf8 character set.
Examples
--------
SELECT CHARSET('abc');
+----------------+
| CHARSET('abc') |
+----------------+
| latin1 |
+----------------+
SELECT CHARSET(CONVERT('abc' USING utf8));
+------------------------------------+
| CHARSET(CONVERT('abc' USING utf8)) |
+------------------------------------+
| utf8 |
+------------------------------------+
SELECT CHARSET(USER());
+-----------------+
| CHARSET(USER()) |
+-----------------+
| utf8 |
+-----------------+
URL: https://mariadb.com/kb/en/charset/https://mariadb.com/kb/en/charset/ H �' MULTIPOLYGONSyntax
------
MultiPolygon(poly1,poly2,...)
Description
-----------
Constructs a WKB MultiPolygon value from a set of WKB
Polygon arguments. If any argument is not a WKB Polygon, the
return value is NULL.
Example
CREATE TABLE gis_multi_polygon (g MULTIPOLYGON);
INSERT INTO gis_multi_polygon VALUES
(MultiPolygonFromText('MULTIPOLYGON(((28 26,28 0,84 0,84
42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67
13,59 13,59 18)))')),
(MPolyFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28
26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59
13,59 18)))')),
(MPolyFromWKB(AsWKB(MultiPolygon(Polygon(LineString(Point(0,
3), Point(3, 3), Point(3, 0), Point(0, 3)))))));
URL: https://mariadb.com/kb/en/multipolygon/https://mariadb.com/kb/en/multipolygon/ I � POINTSyntax
------
Point(x,y)
Description
-----------
Constructs a WKB Point using the given coordinates.
Examples
--------
SET @g = ST_GEOMFROMTEXT('Point(1 1)');
CREATE TABLE gis_point (g POINT);
INSERT INTO gis_point VALUES
(PointFromText('POINT(10 10)')),
(PointFromText('POINT(20 10)')),
(PointFromText('POINT(20 20)')),
(PointFromWKB(AsWKB(PointFromText('POINT(10 20)'))));
URL: https://mariadb.com/kb/en/point/https://mariadb.com/kb/en/point/ J a ) PointOnSurfaceA synonym for ST_PointOnSurface.
URL: https://mariadb.com/kb/en/pointonsurface/https://mariadb.com/kb/en/pointonsurface/ N #* ST_INTERSECTIONSyntax
------
ST_INTERSECTION(g1,g2)
Description
-----------
Returns a geometry that is the intersection, or shared
portion, of geometry g1 and geometry g2.
Examples
--------
SET @g1 = ST_GEOMFROMTEXT('POINT(2 1)');
SET @g2 = ST_GEOMFROMTEXT('LINESTRING(2 1, 0 2)');
SELECT ASTEXT(ST_INTERSECTION(@g1,@g2));
+----------------------------------+
| ASTEXT(ST_INTERSECTION(@g1,@g2)) |
+----------------------------------+
| POINT(2 1) |
+----------------------------------+
URL: https://mariadb.com/kb/en/st_intersection/https://mariadb.com/kb/en/st_intersection/ zj�� ���.dT� } � $ω �F � �' COERCIBILITYSyntax
------
COERCIBILITY(str)
Description
-----------
Returns the collation coercibility value of the string
argument. Coercibility defines what will be converted to
what in case of collation conflict, with an expression with
higher coercibility being converted to the collation of an
expression with lower coercibility.
Coercibility | Description | Example |
0 | Explicit | Value using a COLLATE clause |
1 | No collation | Concatenated strings using different
collations |
2 | Implicit | Column value |
3 | Constant | USER() return value |
4 | Coercible | Literal string |
5 | Ignorable | NULL or derived from NULL |
Examples
--------
SELECT COERCIBILITY('abc' COLLATE latin1_swedish_ci);
+-----------------------------------------------+
| COERCIBILITY('abc' COLLATE latin1_swedish_ci) |
+-----------------------------------------------+
| 0 |
+-----------------------------------------------+
SELECT COERCIBILITY(USER());
+----------------------+
| COERCIBILITY(USER()) |
+----------------------+
| 3 |
+----------------------+
SELECT COERCIBILITY('abc');
+---------------------+
| COERCIBILITY('abc') |
+---------------------+
| 4 |
+---------------------+
URL: https://mariadb.com/kb/en/coercibility/https://mariadb.com/kb/en/coercibility/ � Z' CURRENT_ROLERoles were introduced in MariaDB 10.0.5.
Syntax
------
CURRENT_ROLE, CURRENT_ROLE()
Description
-----------
Returns the current role name. This determines your access
privileges. The return value is a string in the
utf8 character set.
If there is no current role, NULL is returned.
The output of SELECT CURRENT_ROLE is equivalent to the
contents of the ENABLED_ROLES Information Schema table.
USER() returns the combination of user and host used to
login. CURRENT_USER() returns the account used to determine
current connection's privileges.
Examples
--------
SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| NULL |
+--------------+
SET ROLE staff;
SELECT CURRENT_ROLE;
+--------------+
| CURRENT_ROLE |
+--------------+
| staff |
+--------------+
URL: https://mariadb.com/kb/en/current_role/https://mariadb.com/kb/en/current_role/ � r' CURRENT_USERSyntax
------
CURRENT_USER, CURRENT_USER()
Description
-----------
Returns the user name and host name combination for the
MariaDB account
that the server used to authenticate the current client.
This account
determines your access privileges. The return value is a
string in the
utf8 character set.
The value of CURRENT_USER() can differ from the value of
USER(). CURRENT_ROLE() returns the current active role.
Examples
--------
shell> mysql --user="anonymous"
MariaDB [(none)]> select user(),current_user();
+---------------------+----------------+
| user() | current_user() |
+---------------------+----------------+
| anonymous@localhost | @localhost |
+---------------------+----------------+
When calling CURRENT_USER() in a stored procedure, it
returns the owner of the stored procedure, as defined with
DEFINER.
URL: https://mariadb.com/kb/en/current_user/https://mariadb.com/kb/en/current_user/ � n# DATABASESyntax
------
DATABASE()
Description
-----------
Returns the default (current) database name as a string in
the utf8 character set. If there is no default database,
DATABASE() returns NULL. Within a stored routine, the
default database is the database that the routine is
associated with, which is not necessarily the same as the
database that is the default in the calling context.
SCHEMA() is a synonym for DATABASE().
To select a default database, the USE statement can be run.
Another way to set the default database is specifying its
name at mysql command line client startup.
Examples
--------
SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| NULL |
+------------+
USE test;
Database changed
SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| test |
+------------+
URL: https://mariadb.com/kb/en/database/https://mariadb.com/kb/en/database/ � �" DEFAULTSyntax
------
DEFAULT(col_name)
Description
-----------
Returns the default value for a table column. If the column
has no default value, NULL is returned.
For integer columns using AUTO_INCREMENT, 0 is returned.
When using DEFAULT as a value to set in an INSERT or UPDATE
statement, you can use the bare keyword DEFAULT without the
parentheses and argument to
refer to the column in context. You can only use DEFAULT as
a bare keyword if you are using it
alone without a surrounding expression or function.
Examples
--------
Select only non-default values for a column:
SELECT i FROM t WHERE i != DEFAULT(i);
Update values to be one greater than the default value:
UPDATE t SET i = DEFAULT(i)+1 WHERE i
URL: https://mariadb.com/kb/en/default/https://mariadb.com/kb/en/default/ O a, ST_POINTONSURFACEST_POINTONSURFACE() was introduced in MariaDB 10.1.2
Syntax
------
ST_PointOnSurface(g)
PointOnSurface(g)
Description
-----------
Given a geometry, returns a POINT guaranteed to intersect a
surface. However, see MDEV-7514.
ST_PointOnSurface() and PointOnSurface() are synonyms.
URL: https://mariadb.com/kb/en/st_pointonsurface/https://mariadb.com/kb/en/st_pointonsurface/ T �! BINLOGSyntax
------
BINLOG 'str'
Description
-----------
BINLOG is an internal-use statement. It is generated by the
mysqlbinlog program as the printable representation of
certain events
in binary log files. The 'str' value is a base 64-encoded
string the that server decodes to determine the data change
indicated by the
corresponding event. This statement requires the SUPER
privilege. It was added in MySQL 5.1.5.
URL: https://mariadb.com/kb/en/binlog/https://mariadb.com/kb/en/binlog/�Q @ � �V � FLUSH W y, FLUSH QUERY CACHEDescription
-----------
You can defragment the query cache to better utilize its
memory with
the FLUSH QUERY CACHE statement. The statement does not
remove any queries from the cache.
The RESET QUERY CACHE statement removes all query results
from the query cache.
The FLUSH TABLES statement also does this.
URL: https://mariadb.com/kb/en/flush-query-cache/https://mariadb.com/kb/en/flush-query-cache/ [
�% LOAD INDEXSyntax
------
LOAD INDEX INTO CACHE
tbl_index_list [, tbl_index_list] ...
tbl_index_list:
tbl_name
[[INDEX|KEY] (index_name[, index_name] ...)]
[IGNORE LEAVES]
Description
-----------
The LOAD INDEX INTO CACHE statement preloads a table index
into the key
cache to which it has been assigned by an explicit CACHE
INDEX
statement, or into the default key cache otherwise.
LOAD INDEX INTO CACHE is used only for MyISAM or Aria
tables. Until MariaDB 5.3, it was not supported for tables
having user-defined partitioning, but this limitation was
removed in MariaDB 5.5.
The IGNORE LEAVES modifier causes only blocks for the
nonleaf nodes of
the index to be preloaded.
URL: https://mariadb.com/kb/en/load-index/https://mariadb.com/kb/en/load-index/ y -- SHOW FUNCTION CODESyntax
------
SHOW FUNCTION CODE func_name
Description
-----------
SHOW FUNCTION CODE shows a representation of the internal
implementation of the stored function.
It is similar to SHOW PROCEDURE CODE but for stored
functions.
URL: https://mariadb.com/kb/en/show-function-code/https://mariadb.com/kb/en/show-function-code/ z� .�) �[�,/� ���7� +~�\k �/ � �+ DECODE_HISTOGRAMDECODE_HISTOGRAM() was introduced in MariaDB 10.0.2
Syntax
------
DECODE_HISTOGRAM(hist_type,histogram)
Note: Before MariaDB 10.0.10 the arguments were reversed.
Description
-----------
Returns a string of comma separated numeric values
corresponding to a probability distribution represented by
the histogram of type hist_type (SINGLE_PREC_HB or
DOUBLE_PREC_HB). The hist_type and histogram would be
commonly used from the mysql.column_stats table.
See Histogram Based Statistics for details.
Examples
--------
CREATE TABLE origin (
i INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
v INT UNSIGNED NOT NULL
);
INSERT INTO origin(v) VALUES
(1),(2),(3),(4),(5),(10),(20),
(30),(40),(50),(60),(70),(80),
(90),(100),(200),(400),(800);
SET histogram_size=10,histogram_type=SINGLE_PREC_HB;
ANALYZE TABLE origin PERSISTENT FOR ALL;
+-------------+---------+----------+-----------------------------------------+
| Table | Op | Msg_type | Msg_text |
+-------------+---------+----------+-----------------------------------------+
| test.origin | analyze | status | Engine-independent
statistics collected |
| test.origin | analyze | status | OK |
+-------------+---------+----------+-----------------------------------------+
SELECT db_name,table_name,column_name,hist_type,
hex(histogram),decode_histogram(hist_type,histogram)
FROM mysql.column_stats WHERE db_name='test' and
table_name='origin';
+---------+------------+-------------+----------------+----------------------+-------------------------------------------------------------------+
| db_name | table_name | column_name | hist_type |
hex(histogram) | decode_histogram(hist_type,histogram) |
+---------+------------+-------------+----------------+----------------------+-------------------------------------------------------------------+
| test | origin | i | SINGLE_PREC_HB | 0F2D3C5A7887A5C3D2F0
|
0.059,0.118,0.059,0.118,0.118,0.059,0.118,0.118,0.059,0.118,0.059
|
| test | origin | v | SINGLE_PREC_HB | 000001060C0F161C1F7F
|
0.000,0.000,0.004,0.020,0.024,0.012,0.027,0.024,0.012,0.376,0.502
|
+---------+------------+-------------+----------------+----------------------+-------------------------------------------------------------------+
SET histogram_size=20,histogram_type=DOUBLE_PREC_HB;
ANALYZE TABLE origin PERSISTENT FOR ALL;
+-------------+---------+----------+-----------------------------------------+
| Table | Op | Msg_type | Msg_text |
+-------------+---------+----------+-----------------------------------------+
| test.origin | analyze | status | Engine-independent
statistics collected |
| test.origin | analyze | status | OK |
+-------------+---------+----------+-----------------------------------------+
SELECT db_name,table_name,column_name,
hist_type,hex(histogram),decode_histogram(hist_type,histogram)
FROM mysql.column_stats WHERE db_name='test' and
table_name='origin';
+---------+------------+-------------+----------------+------------------------------------------+-----------------------------------------------------------------------------------------+
| db_name | table_name | column_name | hist_type |
hex(histogram) | decode_histogram(hist_type,histogram) |
+---------+------------+-------------+----------------+------------------------------------------+-----------------------------------------------------------------------------------------+
| test | origin | i | DOUBLE_PREC_HB |
0F0F2D2D3C3C5A5A78788787A5A5C3C3D2D2F0F0 |
0.05882,0.11765,0.05882,0.11765,0.11765,0.05882,0.11765,0.11765,0.05882,0.11765,0.05882
|
| test | origin | v | DOUBLE_PREC_HB |
5200F600480116067E0CB30F1B16831CB81FD67F |
0.00125,0.00250,0.00125,0.01877,0.02502,0.01253,0.02502,0.02502,0.01253,0.37546,0.50063
|
URL: https://mariadb.com/kb/en/decode_histogram/https://mariadb.com/kb/en/decode_histogram/ �
�% FOUND_ROWSSyntax
------
FOUND_ROWS()
Description
-----------
A SELECT statement may include a LIMIT clause to restrict
the number
of rows the server returns to the client. In some cases, it
is
desirable to know how many rows the statement would have
returned
without the LIMIT, but without running the statement again.
To obtain
this row count, include a SQL_CALC_FOUND_ROWS option in the
SELECT
statement, and then invoke FOUND_ROWS() afterwards.
You can also use FOUND_ROWS() to obtain the number of rows
returned by a SELECT which does not contain a LIMIT clause.
In this case you don't need to use the SQL_CALC_FOUND_ROWS
option. This can be useful for example in a stored
procedure.
Also, this function works with some other statements which
return a resultset, including SHOW, DESC and HELP. For
DELETE ... RETURNING you should use ROW_COUNT(). It also
works as a prepared statement, or after executing a prepared
statement.
Statements which don't return any results don't affect
FOUND_ROWS() - the previous value will still be returned.
Warning: When used after a CALL statement, this function
returns the number of rows selected by the last query in the
procedure, not by the whole procedure.
Statements using the FOUND_ROWS() function are not safe for
replication.
Examples
--------
SHOW ENGINES;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine | Support | Comment | Transactions | XA |
Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| InnoDB | DEFAULT | Supports transactions, row-level
locking, and foreign keys | YES | YES | YES |
...
| SPHINX | YES | Sphinx storage engine | NO | NO | NO |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
11 rows in set (0.01 sec)
SELECT FOUND_ROWS();
+--------------+
| FOUND_ROWS() |
+--------------+
| 11 |
+--------------+
SELECT SQL_CALC_FOUND_ROWS * FROM tbl_name WHERE id > 100
LIMIT 10;
SELECT FOUND_ROWS();
+--------------+
| FOUND_ROWS() |
+--------------+
| 23 |
+--------------+
URL: https://mariadb.com/kb/en/found_rows/https://mariadb.com/kb/en/found_rows/ �
:( SHOW PROFILESSyntax
------
SHOW PROFILES
Description
-----------
The SHOW PROFILES statement displays profiling information
that indicates resource usage for statements executed during
the course of the
current session. It is used together with
SHOW PROFILE.
URL: https://mariadb.com/kb/en/show-profiles/https://mariadb.com/kb/en/show-profiles/ � `3 SHOW QUERY_RESPONSE_TIMESHOW QUERY_RESPONSE_TIME was introduced in MariaDB 10.1.1.
Starting with MariaDB 10.1.1, which introduced the
Information Schema plugin extension, it is possible to use
SHOW QUERY_RESPONSE_TIME as an alternative for retrieving
information from the QUERY_RESPONSE_TIME plugin.
URL: https://mariadb.com/kb/en/show-query_response_time/https://mariadb.com/kb/en/show-query_response_time/�d @e � �� K., SHOW SLAVE STATUS�f @ � �� �E& SHOW STATUS � � DOSyntax
------
DO expr [, expr] ...
Description
-----------
DO executes the expressions but does not return any
results. In most respects, DO is shorthand for
SELECT expr, ..., but has the advantage that it is slightly
faster when you do not care about the result.
DO is useful primarily with functions that have side
effects, such as RELEASE_LOCK().
URL: https://mariadb.com/kb/en/do/https://mariadb.com/kb/en/do/ ���/ �5 ��N}-! !lN� �+ � ) LAST_INSERT_IDSyntax
------
LAST_INSERT_ID(), LAST_INSERT_ID(expr)
Description
-----------
LAST_INSERT_ID() (no arguments) returns
the first automatically generated value successfully
inserted for an
AUTO_INCREMENT column as a result of the most recently
executed INSERT
statement. The value of LAST_INSERT_ID() remains unchanged
if no rows
are successfully inserted.
If one gives an argument to LAST_INSERT_ID(), then it will
return the value of the expression and
the next call to LAST_INSERT_ID() will return the same
value. The value will also be sent to the client
and can be accessed by the mysql_insert_id function.
For example, after inserting a row that generates an
AUTO_INCREMENT
value, you can get the value like this:
SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 9 |
+------------------+
You can also use LAST_INSERT_ID() to delete the last
inserted row:
DELETE FROM product WHERE id = LAST_INSERT_ID();
If no rows were successfully inserted, LAST_INSERT_ID()
returns 0.
The value of LAST_INSERT_ID() will be consistent across all
versions
if all rows in the INSERT or UPDATE statement were
successful.
The currently executing statement does not affect the value
of
LAST_INSERT_ID(). Suppose that you generate an
AUTO_INCREMENT value
with one statement, and then refer to LAST_INSERT_ID() in a
multiple-row INSERT statement that inserts rows into a table
with its
own AUTO_INCREMENT column. The value of LAST_INSERT_ID()
will remain
stable in the second statement; its value for the second and
later
rows is not affected by the earlier row insertions.
(However, if you
mix references to LAST_INSERT_ID() and LAST_INSERT_ID(expr),
the
effect is undefined.)
If the previous statement returned an error, the value of
LAST_INSERT_ID() is undefined. For transactional tables, if
the
statement is rolled back due to an error, the value of
LAST_INSERT_ID() is left undefined. For manual ROLLBACK, the
value of
LAST_INSERT_ID() is not restored to that before the
transaction; it
remains as it was at the point of the ROLLBACK.
Within the body of a stored routine (procedure or function)
or a
trigger, the value of LAST_INSERT_ID() changes the same way
as for
statements executed outside the body of these kinds of
objects. The
effect of a stored routine or trigger upon the value of
LAST_INSERT_ID() that is seen by following statements
depends on the
kind of routine:
If a stored procedure executes statements that change the
value of LAST_INSERT_ID(), the new value will be seen by
statements that follow the procedure call.
For stored functions and triggers that change the value, the
value is restored when the function or trigger ends, so
following statements will not see a changed value.
Examples
--------
CREATE TABLE t (
id INTEGER UNSIGNED AUTO_INCREMENT PRIMARY KEY,
f VARCHAR(1))
ENGINE = InnoDB;
INSERT INTO t(f) VALUES('a');
SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 1 |
+------------------+
INSERT INTO t(f) VALUES('b');
INSERT INTO t(f) VALUES('c');
SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 3 |
+------------------+
INSERT INTO t(f) VALUES('d'),('e');
SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 4 |
+------------------+
SELECT * FROM t;
+----+------+
| id | f |
+----+------+
| 1 | a |
| 2 | b |
| 3 | c |
| 4 | d |
| 5 | e |
+----+------+
SELECT LAST_INSERT_ID(12);
+--------------------+
| LAST_INSERT_ID(12) |
+--------------------+
| 12 |
+--------------------+
SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 12 |
+------------------+
INSERT INTO t(f) VALUES('f');
SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 6 |
+------------------+
SELECT * FROM t;
+----+------+
| id | f |
+----+------+
| 1 | a |
| 2 | b |
| 3 | c |
| 4 | d |
| 5 | e |
| 6 | f |
+----+------+
SELECT LAST_INSERT_ID(12);
+--------------------+
| LAST_INSERT_ID(12) |
+--------------------+
| 12 |
+--------------------+
INSERT INTO t(f) VALUES('g');
SELECT * FROM t;
+----+------+
| id | f |
+----+------+
| 1 | a |
| 2 | b |
| 3 | c |
| 4 | d |
| 5 | e |
| 6 | f |
| 7 | g |
+----+------+
URL: https://mariadb.com/kb/en/last_insert_id/https://mariadb.com/kb/en/last_insert_id/ � d, PROCEDURE ANALYSESyntax
------
analyse([max_elements[,max_memory]])
Description
-----------
This procedure is defined in the sql/sql_analyse.cc file. It
examines
the result from a query and returns an analysis of the
results that
suggests optimal data types for each column. To obtain this
analysis,
append PROCEDURE ANALYSE to the end of a SELECT statement:
SELECT ... FROM ... WHERE ... PROCEDURE
ANALYSE([max_elements,[max_memory]])
For example:
SELECT col1, col2 FROM table1 PROCEDURE ANALYSE(10, 2000);
The results show some statistics for the values returned by
the query,
and propose an optimal data type for the columns. This can
be helpful
for checking your existing tables, or after importing new
data. You
may need to try different settings for the arguments so that
PROCEDURE
ANALYSE() does not suggest the ENUM data type when it is not
appropriate.
The arguments are optional and are used as follows:
max_elements (default 256) is the maximum number of distinct
values that analyse notices per column. This is used by
analyse to check whether the optimal data type should be of
type ENUM; if there are more than max_elements distinct
values, then ENUM is not a suggested type.
max_memory (default 8192) is the maximum amount of memory
that analyse should allocate per column while trying to find
all distinct values.
URL: https://mariadb.com/kb/en/procedure-analyse/https://mariadb.com/kb/en/procedure-analyse/ � � DUALDescription
-----------
You are allowed to specify DUAL as a dummy table name in
situations where no tables are referenced, such as the
following SELECT statement:
SELECT 1 + 1 FROM DUAL;
+-------+
| 1 + 1 |
+-------+
| 2 |
+-------+
DUAL is purely for the convenience of people who require
that all SELECT statements should have
FROM and possibly other clauses. MariaDB ignores the
clauses. MariaDB does not require FROM DUAL if no tables
are referenced.
FROM DUAL could be used when you only SELECT computed
values, but require a WHERE clause, perhaps to test that a
script correctly handles empty resultsets:
SELECT 1 FROM DUAL WHERE FALSE;
Empty set (0.00 sec)
URL: https://mariadb.com/kb/en/dual/https://mariadb.com/kb/en/dual/ �
n% FOR UPDATEThe FOR UPDATE clause of SELECT applies only when autocommit
is set to 0 or the SELECT is enclosed in a transaction. A
lock is acquired on the rows, and other transactions are
prevented from writing the rows, acquire locks, and from
reading them (unless their isolation level is READ
UNCOMMITTED).
If autocommit is set to 1, the LOCK IN SHARE MODE and FOR
UPDATE clauses have no effect.
If the isolation level is set to SERIALIZABLE, all plain
SELECT statements are converted to SELECT ... LOCK IN SHARE
MODE.
Example
SELECT * FROM trans WHERE period=2001 FOR UPDATE;
URL: https://mariadb.com/kb/en/for-update/https://mariadb.com/kb/en/for-update/ �c� W��c� �, �
�
% LAST_VALUESyntax
------
LAST_VALUE(expr,[expr,...])
LAST_VALUE(expr) OVER (
[ PARTITION BY partition_expression ]
[ ORDER BY order_list ]
)
Description
-----------
LAST_VALUE() evaluates all expressions and returns the last.
This is useful together with setting user variables to a
value with @var:=expr, for example when you want to get data
of rows updated/deleted without having to do two queries
against the table.
Since MariaDB 10.2.2, LAST_VALUE can be used as a window
function.
Returns NULL if no last value exists.
Examples
--------
CREATE TABLE t1 (a int, b int);
INSERT INTO t1 VALUES(1,10),(2,20);
DELETE FROM t1 WHERE a=1 AND last_value(@a:=a,@b:=b,1);
SELECT @a,@b;
+------+------+
| @a | @b |
+------+------+
| 1 | 10 |
+------+------+
As a window function:
CREATE TABLE t1 (
pk int primary key,
a int,
b int,
c char(10),
d decimal(10, 3),
e real
);
INSERT INTO t1 VALUES
( 1, 0, 1, 'one', 0.1, 0.001),
( 2, 0, 2, 'two', 0.2, 0.002),
( 3, 0, 3, 'three', 0.3, 0.003),
( 4, 1, 2, 'three', 0.4, 0.004),
( 5, 1, 1, 'two', 0.5, 0.005),
( 6, 1, 1, 'one', 0.6, 0.006),
( 7, 2, NULL, 'n_one', 0.5, 0.007),
( 8, 2, 1, 'n_two', NULL, 0.008),
( 9, 2, 2, NULL, 0.7, 0.009),
(10, 2, 0, 'n_four', 0.8, 0.010),
(11, 2, 10, NULL, 0.9, NULL);
SELECT pk, FIRST_VALUE(pk) OVER (ORDER BY pk) AS first_asc,
LAST_VALUE(pk) OVER (ORDER BY pk) AS last_asc,
FIRST_VALUE(pk) OVER (ORDER BY pk DESC) AS first_desc,
LAST_VALUE(pk) OVER (ORDER BY pk DESC) AS last_desc
FROM t1
ORDER BY pk DESC;
+----+-----------+----------+------------+-----------+
| pk | first_asc | last_asc | first_desc | last_desc |
+----+-----------+----------+------------+-----------+
| 11 | 1 | 11 | 11 | 11 |
| 10 | 1 | 10 | 11 | 10 |
| 9 | 1 | 9 | 11 | 9 |
| 8 | 1 | 8 | 11 | 8 |
| 7 | 1 | 7 | 11 | 7 |
| 6 | 1 | 6 | 11 | 6 |
| 5 | 1 | 5 | 11 | 5 |
| 4 | 1 | 4 | 11 | 4 |
| 3 | 1 | 3 | 11 | 3 |
| 2 | 1 | 2 | 11 | 2 |
| 1 | 1 | 1 | 11 | 1 |
+----+-----------+----------+------------+-----------+
CREATE OR REPLACE TABLE t1 (i int);
INSERT INTO t1 VALUES
(1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
SELECT i,
FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW
and 1 FOLLOWING) AS f_1f,
LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW and
1 FOLLOWING) AS l_1f,
FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING
AND 1 FOLLOWING) AS f_1p1f,
LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING AND
1 FOLLOWING) AS f_1p1f,
FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING
AND 1 PRECEDING) AS f_2p1p,
LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING AND
1 PRECEDING) AS f_2p1p,
FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING
AND 2 FOLLOWING) AS f_1f2f,
LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING AND
2 FOLLOWING) AS f_1f2f
FROM t1;
+------+------+------+--------+--------+--------+--------+--------+--------+
| i | f_1f | l_1f | f_1p1f | f_1p1f | f_2p1p | f_2p1p |
f_1f2f | f_1f2f |
+------+------+------+--------+--------+--------+--------+--------+--------+
| 1 | 1 | 2 | 1 | 2 | NULL | NULL | 2 | 3 |
| 2 | 2 | 3 | 1 | 3 | 1 | 1 | 3 | 4 |
| 3 | 3 | 4 | 2 | 4 | 1 | 2 | 4 | 5 |
| 4 | 4 | 5 | 3 | 5 | 2 | 3 | 5 | 6 |
| 5 | 5 | 6 | 4 | 6 | 3 | 4 | 6 | 7 |
| 6 | 6 | 7 | 5 | 7 | 4 | 5 | 7 | 8 |
| 7 | 7 | 8 | 6 | 8 | 5 | 6 | 8 | 9 |
| 8 | 8 | 9 | 7 | 9 | 6 | 7 | 9 | 10 |
| 9 | 9 | 10 | 8 | 10 | 7 | 8 | 10 | 10 |
| 10 | 10 | 10 | 9 | 10 | 8 | 9 | NULL | NULL |
+------+------+------+--------+--------+--------+--------+--------+--------+
URL: https://mariadb.com/kb/en/last_value/https://mariadb.com/kb/en/last_value/ � �
$ ROW_COUNTSyntax
------
ROW_COUNT()
Description
-----------
ROW_COUNT() returns the number of rows updated, inserted or
deleted
by the preceding statement. This is the same as the row
count that the
mysql client displays and the value from the
mysql_affected_rows() C
API function.
Generally:
For statements which return a result set (such as SELECT,
SHOW, DESC or HELP), returns -1, even when the result set is
empty. This is also true for administrative statements, such
as OPTIMIZE.
For DML statements other than SELECT and for ALTER TABLE,
returns the number of affected rows.
For DDL statements (including TRUNCATE) and for other
statements which don't return any result set (such as USE,
DO, SIGNAL or DEALLOCATE PREPARE), returns 0.
For UPDATE, affected rows is by default the number of rows
that were actually changed. If the CLIENT_FOUND_ROWS flag to
mysql_real_connect() is specified when connecting to mysqld,
affected rows is instead the number of rows matched by the
WHERE clause.
For REPLACE, deleted rows are also counted. So, if REPLACE
deletes a row and adds a new row, ROW_COUNT() returns 2.
For INSERT ... ON DUPLICATE KEY, updated rows are counted
twice. So, if INSERT adds a new rows and modifies another
row, ROW_COUNT() returns 3.
ROW_COUNT() does not take into account rows that are not
directly deleted/updated by the last statement. This means
that rows deleted by foreign keys or triggers are not
counted.
Warning: You can use ROW_COUNT() with prepared statements,
but you need to call it after EXECUTE, not after DEALLOCATE
PREPARE, because the row count for allocate prepare is
always 0.
Warning: When used after a CALL statement, this function
returns the number of rows affected by the last statement in
the procedure, not by the whole procedure.
Warning: After INSERT DELAYED, ROW_COUNT() returns the
number of the rows you tried to insert, not the number of
the successful writes.
This information can also be found in the diagnostics area.
Statements using the ROW_COUNT() function are not safe for
replication.
Examples
--------
CREATE TABLE t (A INT);
INSERT INTO t VALUES(1),(2),(3);
SELECT ROW_COUNT();
+-------------+
| ROW_COUNT() |
+-------------+
| 3 |
+-------------+
DELETE FROM t WHERE A IN(1,2);
SELECT ROW_COUNT();
+-------------+
| ROW_COUNT() |
+-------------+
| 2 |
+-------------+
Example with prepared statements:
SET @q = 'INSERT INTO t VALUES(1),(2),(3);';
PREPARE stmt FROM @q;
EXECUTE stmt;
Query OK, 3 rows affected (0.39 sec)
Records: 3 Duplicates: 0 Warnings: 0
SELECT ROW_COUNT();
+-------------+
| ROW_COUNT() |
+-------------+
| 3 |
+-------------+
URL: https://mariadb.com/kb/en/row_count/https://mariadb.com/kb/en/row_count/ � � + HANDLER CommandsSyntax
------
HANDLER tbl_name OPEN [ [AS] alias]
HANDLER tbl_name READ index_name { = | >= | = |
URL: https://mariadb.com/kb/en/handler-commands/https://mariadb.com/kb/en/handler-commands/ � �- LOCK IN SHARE MODEWhen LOCK IN SHARE MODE is specified in a SELECT statement,
MariaDB will wait until all transactions that have modified
the rows are committed. Then, a write lock is acquired. All
transactions can read the rows, but if they want to modify
them, they have to wait until your transaction is committed.
InnoDB/XtraDB supports row-level locking. selected rows can
be locked using LOCK IN SHARE MODE or FOR UPDATE. In both
cases, a lock is acquired on the rows read by the query, and
it will be released when the current transaction is
committed.
If autocommit is set to 1, the LOCK IN SHARE MODE and FOR
UPDATE clauses have no effect.
URL: https://mariadb.com/kb/en/lock-in-share-mode/https://mariadb.com/kb/en/lock-in-share-mode/ ���� "�
��2�
�V � ] USERSyntax
------
USER()
Description
-----------
Returns the current MariaDB user name and host name, given
when authenticating to MariaDB, as a string in the utf8
character set.
Note that the value of USER() may differ from the value of
CURRENT_USER(), which is the user used to authenticate the
current client.
CURRENT_ROLE() returns the current active role.
SYSTEM_USER() and SESSION_USER are synonyms for USER().
Statements using the USER() function or one of its synonyms
are not safe for statement level replication.
Examples
--------
shell> mysql --user="anonymous"
MariaDB [(none)]> select user(),current_user();
+---------------------+----------------+
| user() | current_user() |
+---------------------+----------------+
| anonymous@localhost | @localhost |
+---------------------+----------------+
URL: https://mariadb.com/kb/en/user/https://mariadb.com/kb/en/user/ � "" VERSIONSyntax
------
VERSION()
Description
-----------
Returns a string that indicates the MariaDB server version.
The string
uses the utf8 character set.
Examples
--------
SELECT VERSION();
+----------------+
| VERSION() |
+----------------+
| 10.4.7-MariaDB |
+----------------+
The VERSION() string may have one or more of the following
suffixes:
Suffix | Description |
-embedded | The server is an embedded server (libmysqld). |
-log | General logging, slow logging or binary (replication)
logging is enabled. |
-debug | The server is compiled for debugging. |
-valgrind | The server is compiled to be instrumented with
valgrind. |
Changing the Version String
Some old legacy code may break because they are parsing the
VERSION string and expecting a MySQL string or a simple
version
string like Joomla til API17, see MDEV-7780.
From MariaDB 10.2, one can fool these applications by
setting the version string from the command line or the
my.cnf files with --version=....
URL: https://mariadb.com/kb/en/version/https://mariadb.com/kb/en/version/ � �$ Not Equal OperatorSyntax
------
, !=
Description
-----------
Not equal operator. Evaluates both SQL expressions and
returns 1 if they are not equal and 0 if they are equal, or
NULL if either expression is NULL. If the expressions return
different data types, (for instance, a number and a string),
performs type conversion.
When used in row comparisons these two queries return the
same results:
SELECT (t1.a, t1.b) != (t2.x, t2.y)
FROM t1 INNER JOIN t2;
SELECT (t1.a != t2.x) OR (t1.b != t2.y)
FROM t1 INNER JOIN t2;
Examples
--------
SELECT '.01' '0.01';
+-----------------+
| '.01' '0.01' |
+-----------------+
| 1 |
+-----------------+
SELECT .01 '0.01';
+---------------+
| .01 '0.01' |
+---------------+
| 0 |
+---------------+
SELECT 'zapp' 'zappp';
+-------------------+
| 'zapp' 'zappp' |
+-------------------+
| 1 |
+-------------------+
URL: https://mariadb.com/kb/en/not-equal/https://mariadb.com/kb/en/not-equal/ � �* <=>Syntax
------
Description
-----------
NULL-safe equal operator. It performs an equality comparison
like
the = operator, but returns 1 rather than NULL if both
operands are
NULL, and 0 rather than NULL if one operand is NULL.
a b is equivalent to a = b OR (a IS NULL AND b IS NULL).
When used in row comparisons these two queries return the
same results:
SELECT (t1.a, t1.b) (t2.x, t2.y)
FROM t1 INNER JOIN t2;
SELECT (t1.a t2.x) AND (t1.b t2.y)
FROM t1 INNER JOIN t2;
See also NULL Values in MariaDB.
Examples
--------
SELECT 1 1, NULL NULL, 1 NULL;
+---------+---------------+------------+
| 1 1 | NULL NULL | 1 NULL |
+---------+---------------+------------+
| 1 | 1 | 0 |
+---------+---------------+------------+
SELECT 1 = 1, NULL = NULL, 1 = NULL;
+-------+-------------+----------+
| 1 = 1 | NULL = NULL | 1 = NULL |
+-------+-------------+----------+
| 1 | NULL | NULL |
+-------+-------------+----------+
URL: https://mariadb.com/kb/en/null-safe-equal/https://mariadb.com/kb/en/null-safe-equal/ � � =Syntax
------
left_expr = right_expr
Description
-----------
Equal operator. Evaluates both SQL expressions and returns 1
if they are equal, 0 if they are not equal, or NULL if
either expression is NULL. If the expressions return
different data types (for example, a number and a string), a
type conversion is performed.
When used in row comparisons these two queries are
synonymous and return the same results:
SELECT (t1.a, t1.b) = (t2.x, t2.y) FROM t1 INNER JOIN t2;
SELECT (t1.a = t2.x) AND (t1.b = t2.y) FROM t1 INNER JOIN
t2;
To perform a NULL-safe comparison, use the operator.
= can also be used as an assignment operator.
Examples
--------
SELECT 1 = 0;
+-------+
| 1 = 0 |
+-------+
| 0 |
+-------+
SELECT '0' = 0;
+---------+
| '0' = 0 |
+---------+
| 1 |
+---------+
SELECT '0.0' = 0;
+-----------+
| '0.0' = 0 |
+-----------+
| 1 |
+-----------+
SELECT '0.01' = 0;
+------------+
| '0.01' = 0 |
+------------+
| 0 |
+------------+
SELECT '.01' = 0.01;
+--------------+
| '.01' = 0.01 |
+--------------+
| 1 |
+--------------+
SELECT (5 * 2) = CONCAT('1', '0');
+----------------------------+
| (5 * 2) = CONCAT('1', '0') |
+----------------------------+
| 1 |
+----------------------------+
SELECT 1 = NULL;
+----------+
| 1 = NULL |
+----------+
| NULL |
+----------+
SELECT NULL = NULL;
+-------------+
| NULL = NULL |
+-------------+
| NULL |
+-------------+
URL: https://mariadb.com/kb/en/equal/https://mariadb.com/kb/en/equal/ � 4$ PROCEDUREThe PROCEDURE clause of SELECT passes the whole result set
to a Procedure which will process it. These Procedures are
not Stored Procedures, and can only be written in the C
language, so it is necessary to recompile the server.
Currently, the only available procedure is ANALYSE, which
examines the resultset and suggests the optimal datatypes
for each column. It is defined in the sql/sql_analyse.cc
file, and can be used as an example to create more
Procedures.
This clause cannot be used in a view's definition.
URL: https://mariadb.com/kb/en/procedure/https://mariadb.com/kb/en/procedure/�| @
� �� �E" EXPLAIN � � * EXPLAIN ANALYZEThe syntax for the EXPLAIN ANALYZE feature was changed to
ANALYZE statement, available since MariaDB 10.1.0. See
ANALYZE statement.
URL: https://mariadb.com/kb/en/explain-analyze/https://mariadb.com/kb/en/explain-analyze/ � �# CONTAINSSyntax
------
Contains(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether a geometry g1 completely
contains geometry g2. CONTAINS() is based on the original
MySQL implementation and uses object bounding rectangles,
while ST_CONTAINS() uses object shapes.
This tests the opposite relationship to Within().
URL: https://mariadb.com/kb/en/contains/https://mariadb.com/kb/en/contains/ � �" CROSSESSyntax
------
Crosses(g1,g2)
Description
-----------
Returns 1 if g1 spatially crosses g2. Returns NULL if g1 is
a Polygon or a MultiPolygon, or if g2 is a
Point or a MultiPoint. Otherwise, returns 0.
The term spatially crosses denotes a spatial relation
between two
given geometries that has the following properties:
The two geometries intersect
Their intersection results in a geometry that has a
dimension that is one
less than the maximum dimension of the two given geometries
Their intersection is not equal to either of the two given
geometries
CROSSES() is based on the original MySQL implementation, and
uses object bounding rectangles, while ST_CROSSES() uses
object shapes.
URL: https://mariadb.com/kb/en/crosses/https://mariadb.com/kb/en/crosses/ X&���
f+ �o�� 6���Y ��nUS �� � ' >Syntax
------
>
Description
-----------
Greater than operator. Evaluates both SQL expressions and
returns 1 if the left value is greater than the right value
and 0 if it is not, or NULL if either expression is NULL. If
the expressions return different data types, (for instance,
a number and a string), performs type conversion.
When used in row comparisons these two queries return the
same results:
SELECT (t1.a, t1.b) > (t2.x, t2.y)
FROM t1 INNER JOIN t2;
SELECT (t1.a > t2.x) OR ((t1.a = t2.x) AND (t1.b > t2.y))
FROM t1 INNER JOIN t2;
Examples
--------
SELECT 2 > 2;
+-------+
| 2 > 2 |
+-------+
| 0 |
+-------+
SELECT 'b' > 'a';
+-----------+
| 'b' > 'a' |
+-----------+
| 1 |
+-----------+
URL: https://mariadb.com/kb/en/greater-than/https://mariadb.com/kb/en/greater-than/ � 70 >=Syntax
------
>=
Description
-----------
Greater than or equal operator. Evaluates both SQL
expressions and returns 1 if the left value is greater than
or equal to the right value and 0 if it is not, or NULL if
either expression is NULL. If the expressions return
different data types, (for instance, a number and a string),
performs type conversion.
When used in row comparisons these two queries return the
same results:
SELECT (t1.a, t1.b) >= (t2.x, t2.y)
FROM t1 INNER JOIN t2;
SELECT (t1.a > t2.x) OR ((t1.a = t2.x) AND (t1.b >= t2.y))
FROM t1 INNER JOIN t2;
Examples
--------
SELECT 2 >= 2;
+--------+
| 2 >= 2 |
+--------+
| 1 |
+--------+
SELECT 'A' >= 'a';
+------------+
| 'A' >= 'a' |
+------------+
| 1 |
+------------+
URL: https://mariadb.com/kb/en/greater-than-or-equal/https://mariadb.com/kb/en/greater-than-or-equal/ � �# COALESCESyntax
------
COALESCE(value,...)
Description
-----------
Returns the first non-NULL value in the list, or NULL if
there are no
non-NULL values. At least one parameter must be passed.
See also NULL Values in MariaDB.
Examples
--------
SELECT COALESCE(NULL,1);
+------------------+
| COALESCE(NULL,1) |
+------------------+
| 1 |
+------------------+
SELECT COALESCE(NULL,NULL,NULL);
+--------------------------+
| COALESCE(NULL,NULL,NULL) |
+--------------------------+
| NULL |
+--------------------------+
When two arguments are given, COALESCE() is the same as
IFNULL():
SET @a=NULL, @b=1;
SELECT COALESCE(@a, @b), IFNULL(@a, @b);
+------------------+----------------+
| COALESCE(@a, @b) | IFNULL(@a, @b) |
+------------------+----------------+
| 1 | 1 |
+------------------+----------------+
Hex type confusion:
CREATE TABLE t1 (a INT, b VARCHAR(10));
INSERT INTO t1 VALUES (0x31, 0x61),(COALESCE(0x31),
COALESCE(0x61));
SELECT * FROM t1;
+------+------+
| a | b |
+------+------+
| 49 | a |
| 1 | a |
+------+------+
The reason for the differing results above is that when 0x31
is inserted directly to the column, it's treated as a
number (see Hexadecimal Literals), while when 0x31 is passed
to COALESCE(), it's treated as a string, because:
HEX values have a string data type by default.
COALESCE() has the same data type as the argument.
URL: https://mariadb.com/kb/en/coalesce/https://mariadb.com/kb/en/coalesce/ � � INSyntax
------
expr IN (value,...)
Description
-----------
Returns 1 if expr is equal to any of the values in the IN
list, else
returns 0. If all values are constants, they are evaluated
according
to the type of expr and sorted. The search for the item then
is done
using a binary search. This means IN is very quick if the IN
value
list consists entirely of constants. Otherwise, type
conversion takes
place according to the rules described at Type Conversion,
but
applied to all the arguments.
If expr is NULL, IN always returns NULL. If at least one of
the values in the list is NULL, and one of the comparisons
is true, the result is 1. If at least one of the values in
the list is NULL and none of the comparisons is true, the
result is NULL.
Examples
--------
SELECT 2 IN (0,3,5,7);
+----------------+
| 2 IN (0,3,5,7) |
+----------------+
| 0 |
+----------------+
SELECT 'wefwf' IN ('wee','wefwf','weg');
+----------------------------------+
| 'wefwf' IN ('wee','wefwf','weg') |
+----------------------------------+
| 1 |
+----------------------------------+
Type conversion:
SELECT 1 IN ('1', '2', '3');
+----------------------+
| 1 IN ('1', '2', '3') |
+----------------------+
| 1 |
+----------------------+
SELECT NULL IN (1, 2, 3);
+-------------------+
| NULL IN (1, 2, 3) |
+-------------------+
| NULL |
+-------------------+
MariaDB [(none)]> SELECT 1 IN (1, 2, NULL);
+-------------------+
| 1 IN (1, 2, NULL) |
+-------------------+
| 1 |
+-------------------+
MariaDB [(none)]> SELECT 5 IN (1, 2, NULL);
+-------------------+
| 5 IN (1, 2, NULL) |
+-------------------+
| NULL |
+-------------------+
URL: https://mariadb.com/kb/en/in/https://mariadb.com/kb/en/in/ � �# DISJOINTSyntax
------
Disjoint(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether g1 is spatially disjoint
from
(does not intersect) g2.
DISJOINT() tests the opposite relationship to INTERSECTS().
DISJOINT() is based on the original MySQL implementation and
uses object bounding rectangles, while ST_DISJOINT() uses
object shapes.
URL: https://mariadb.com/kb/en/disjoint/https://mariadb.com/kb/en/disjoint/ � �! EQUALSSyntax
------
Equals(g1,g2)
From MariaDB 10.2.3:
MBREQUALS(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether g1 is spatially equal to
g2.
EQUALS() is based on the original MySQL implementation and
uses object bounding rectangles, while ST_EQUALS() uses
object shapes.
From MariaDB 10.2.3, MBREQUALS is a synonym for Equals.
URL: https://mariadb.com/kb/en/equals/https://mariadb.com/kb/en/equals/ �
�% INTERSECTSSyntax
------
INTERSECTS(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether geometry g1 spatially
intersects geometry g2.
INTERSECTS() is based on the original MySQL implementation
and uses object bounding rectangles, while ST_INTERSECTS()
uses object shapes.
INTERSECTS() tests the opposite relationship to DISJOINT().
URL: https://mariadb.com/kb/en/intersects/https://mariadb.com/kb/en/intersects/ � �# OVERLAPSSyntax
------
OVERLAPS(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether g1 spatially overlaps g2.
The term spatially overlaps is used if two geometries
intersect and their
intersection results in a geometry of the same dimension but
not equal to
either of the given geometries.
OVERLAPS() is based on the original MySQL implementation and
uses object bounding rectangles, while ST_OVERLAPS() uses
object shapes.
URL: https://mariadb.com/kb/en/overlaps/https://mariadb.com/kb/en/overlaps/ �
�( ST_DIFFERENCESyntax
------
ST_DIFFERENCE(g1,g2)
Description
-----------
Returns a geometry representing the point set difference of
the given geometry values.
Example
SET @g1 = POINT(10,10), @g2 = POINT(20,20);
SELECT ST_AsText(ST_Difference(@g1, @g2));
+------------------------------------+
| ST_AsText(ST_Difference(@g1, @g2)) |
+------------------------------------+
| POINT(10 10) |
+------------------------------------+
URL: https://mariadb.com/kb/en/st_difference/https://mariadb.com/kb/en/st_difference/ �*�&��%�X�� ���Qz E�B+� � � U ISSyntax
------
IS boolean_value
Description
-----------
Tests a value against a boolean value, where boolean_value
can be
TRUE, FALSE, or UNKNOWN.
There is an important difference between using IS TRUE or
comparing a value with TRUE using =. When using =, only 1
equals to TRUE. But when using IS TRUE, all values which are
logically true (like a number > 1) return TRUE.
Examples
--------
SELECT 1 IS TRUE, 0 IS FALSE, NULL IS UNKNOWN;
+-----------+------------+-----------------+
| 1 IS TRUE | 0 IS FALSE | NULL IS UNKNOWN |
+-----------+------------+-----------------+
| 1 | 1 | 1 |
+-----------+------------+-----------------+
Difference between = and IS TRUE:
SELECT 2 = TRUE, 2 IS TRUE;
+----------+-----------+
| 2 = TRUE | 2 IS TRUE |
+----------+-----------+
| 0 | 1 |
+----------+-----------+
URL: https://mariadb.com/kb/en/is/https://mariadb.com/kb/en/is/ �
! IS NOTSyntax
------
IS NOT boolean_value
Description
-----------
Tests a value against a boolean value, where boolean_value
can be
TRUE, FALSE, or UNKNOWN.
Examples
--------
SELECT 1 IS NOT UNKNOWN, 0 IS NOT UNKNOWN, NULL IS NOT
UNKNOWN;
+------------------+------------------+---------------------+
| 1 IS NOT UNKNOWN | 0 IS NOT UNKNOWN | NULL IS NOT UNKNOWN
|
+------------------+------------------+---------------------+
| 1 | 1 | 0 |
+------------------+------------------+---------------------+
SELECT NULL IS NOT TRUE, NULL IS NOT FALSE;
+------------------+-------------------+
| NULL IS NOT TRUE | NULL IS NOT FALSE |
+------------------+-------------------+
| 1 | 1 |
+------------------+-------------------+
URL: https://mariadb.com/kb/en/is-not/https://mariadb.com/kb/en/is-not/ � �" IS NULLSyntax
------
IS NULL
Description
-----------
Tests whether a value is NULL. See also NULL Values in
MariaDB.
Examples
--------
SELECT 1 IS NULL, 0 IS NULL, NULL IS NULL;
+-----------+-----------+--------------+
| 1 IS NULL | 0 IS NULL | NULL IS NULL |
+-----------+-----------+--------------+
| 0 | 0 | 1 |
+-----------+-----------+--------------+
Compatibility
Some ODBC applications use the syntax auto_increment_field
IS NOT NULL to find the latest row that was inserted with an
autogenerated key value. If your applications need this, you
can set the sql_auto_is_null variable to 1.
SET @@sql_auto_is_null=1;
CREATE TABLE t1 (auto_increment_column INT NOT NULL
AUTO_INCREMENT PRIMARY KEY);
INSERT INTO t1 VALUES (NULL);
SELECT * FROM t1 WHERE auto_increment_column IS NULL;
+-----------------------+
| auto_increment_column |
+-----------------------+
| 1 |
+-----------------------+
URL: https://mariadb.com/kb/en/is-null/https://mariadb.com/kb/en/is-null/ � I LEASTSyntax
------
LEAST(value1,value2,...)
Description
-----------
With two or more arguments, returns the smallest
(minimum-valued)
argument. The arguments are compared using the following
rules:
If the return value is used in an INTEGER context or all
arguments are integer-valued, they are compared as integers.
If the return value is used in a REAL context or all
arguments are real-valued, they are compared as reals.
If any argument is a case-sensitive string, the arguments
are compared as case-sensitive strings.
In all other cases, the arguments are compared as
case-insensitive strings.
LEAST() returns NULL if any argument is NULL.
Examples
--------
SELECT LEAST(2,0);
+------------+
| LEAST(2,0) |
+------------+
| 0 |
+------------+
SELECT LEAST(34.0,3.0,5.0,767.0);
+---------------------------+
| LEAST(34.0,3.0,5.0,767.0) |
+---------------------------+
| 3.0 |
+---------------------------+
SELECT LEAST('B','A','C');
+--------------------+
| LEAST('B','A','C') |
+--------------------+
| A |
+--------------------+
URL: https://mariadb.com/kb/en/least/https://mariadb.com/kb/en/least/ � 0& NOT BETWEENSyntax
------
expr NOT BETWEEN min AND max
Description
-----------
This is the same as NOT (expr BETWEEN min AND max).
Note that the meaning of the alternative form NOT expr
BETWEEN min AND max is affected by the HIGH_NOT_PRECEDENCE
SQL_MODE flag.
Examples
--------
SELECT 1 NOT BETWEEN 2 AND 3;
+-----------------------+
| 1 NOT BETWEEN 2 AND 3 |
+-----------------------+
| 1 |
+-----------------------+
SELECT 'b' NOT BETWEEN 'a' AND 'c';
+-----------------------------+
| 'b' NOT BETWEEN 'a' AND 'c' |
+-----------------------------+
| 0 |
+-----------------------------+
NULL:
SELECT 1 NOT BETWEEN 1 AND NULL;
+--------------------------+
| 1 NOT BETWEEN 1 AND NULL |
+--------------------------+
| NULL |
+--------------------------+
URL: https://mariadb.com/kb/en/not-between/https://mariadb.com/kb/en/not-between/ � i! NOT INSyntax
------
expr NOT IN (value,...)
Description
-----------
This is the same as NOT (expr IN (value,...)).
Examples
--------
SELECT 2 NOT IN (0,3,5,7);
+--------------------+
| 2 NOT IN (0,3,5,7) |
+--------------------+
| 1 |
+--------------------+
SELECT 'wefwf' NOT IN ('wee','wefwf','weg');
+--------------------------------------+
| 'wefwf' NOT IN ('wee','wefwf','weg') |
+--------------------------------------+
| 0 |
+--------------------------------------+
SELECT 1 NOT IN ('1', '2', '3');
+--------------------------+
| 1 NOT IN ('1', '2', '3') |
+--------------------------+
| 0 |
+--------------------------+
NULL:
SELECT NULL NOT IN (1, 2, 3);
+-----------------------+
| NULL NOT IN (1, 2, 3) |
+-----------------------+
| NULL |
+-----------------------+
SELECT 1 NOT IN (1, 2, NULL);
+-----------------------+
| 1 NOT IN (1, 2, NULL) |
+-----------------------+
| 0 |
+-----------------------+
SELECT 5 NOT IN (1, 2, NULL);
+-----------------------+
| 5 NOT IN (1, 2, NULL) |
+-----------------------+
| NULL |
+-----------------------+
URL: https://mariadb.com/kb/en/not-in/https://mariadb.com/kb/en/not-in/ � �& ST_DISTANCEST_DISTANCE() was introduced in MariaDB 5.3.3.
Syntax
------
ST_DISTANCE(g1,g2)
Description
-----------
Returns the distance between two geometries, or null if not
given valid inputs.
Example
SELECT ST_Distance(POINT(1,2),POINT(2,2));
+------------------------------------+
| ST_Distance(POINT(1,2),POINT(2,2)) |
+------------------------------------+
| 1 |
+------------------------------------+
URL: https://mariadb.com/kb/en/st_distance/https://mariadb.com/kb/en/st_distance/ � �$ ST_LENGTHSyntax
------
ST_LENGTH(ls)
Description
-----------
Returns as a double-precision number the length of the
LineString value ls in its associated spatial reference.
Examples
--------
SET @ls = 'LineString(1 1,2 2,3 3)';
SELECT ST_LENGTH(ST_GeomFromText(@ls));
+---------------------------------+
| ST_LENGTH(ST_GeomFromText(@ls)) |
+---------------------------------+
| 2.82842712474619 |
+---------------------------------+
URL: https://mariadb.com/kb/en/st_length/https://mariadb.com/kb/en/st_length/ � & ST_OVERLAPSSyntax
------
ST_OVERLAPS(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether geometry g1 spatially
overlaps geometry g2.
The term spatially overlaps is used if two geometries
intersect and their
intersection results in a geometry of the same dimension but
not equal to
either of the given geometries.
ST_OVERLAPS() uses object shapes, while OVERLAPS(), based on
the original MySQL implementation, uses object bounding
rectangles.
URL: https://mariadb.com/kb/en/st-overlaps/https://mariadb.com/kb/en/st-overlaps/ zAS'@��3o�
|���? �|?� �� � ' & ParenthesesParentheses are sometimes called precedence operators - this
means that they can be used to change the other operator's
precedence in an expression. The expressions that are
written between parentheses are computed before the
expressions that are written outside. Parentheses must
always contain an expression (that is, they cannot be
empty), and can be nested.
For example, the following expressions could return
different results:
NOT a OR b
NOT (a OR b)
In the first case, NOT applies to a, so if a is FALSE or b
is TRUE, the expression returns TRUE. In the second case,
NOT applies to the result of a OR b, so if at least one of a
or b is TRUE, the expression is TRUE.
When the precedence of operators is not intuitive, you can
use parentheses to make it immediately clear for whoever
reads the statement.
The precedence of the NOT operator can also be affected by
the HIGH_NOT_PRECEDENCE SQL_MODE flag.
Other uses
Parentheses must always be used to enclose subqueries.
Parentheses can also be used in a JOIN statement between
multiple tables to determine which tables must be joined
first.
Also, parentheses are used to enclose the list of parameters
to be passed to built-in functions, user-defined functions
and stored routines. However, when no parameter is passed to
a stored procedure, parentheses are optional. For builtin
functions and user-defined functions, spaces are not allowed
between the function name and the open parenthesis, unless
the IGNORE_SPACE SQL_MODE is set. For stored routines (and
for functions if IGNORE_SPACE is set) spaces are allowed
before the open parenthesis, including tab characters and
new line characters.
Syntax errors
If there are more open parentheses than closed parentheses,
the error usually looks like this:
ERROR 1064 (42000): You have an error in your SQL syntax;
check the manual that
corresponds to your MariaDB server version for the right
syntax to use near '' a
t line 1
Note the empty string.
If there are more closed parentheses than open parentheses,
the error usually looks like this:
ERROR 1064 (42000): You have an error in your SQL syntax;
check the manual that
corresponds to your MariaDB server version for the right
syntax to use near ')'
at line 1
Note the quoted closed parenthesis.
URL: https://mariadb.com/kb/en/parentheses/https://mariadb.com/kb/en/parentheses/ �
j( ANALYZE TABLESyntax
------
ANALYZE [NO_WRITE_TO_BINLOG | LOCAL] TABLE tbl_name
[,tbl_name ...]
[PERSISTENT FOR [ALL|COLUMNS ([col_name [,col_name ...]])]
[INDEXES ([index_name [,index_name ...]])]]
Description
-----------
ANALYZE TABLE analyzes and stores the key distribution for a
table (index statistics). During the analysis, the table is
locked with a read lock. This statement works with MyISAM,
Aria and InnoDB tables. For MyISAM tables, this statement is
equivalent
to using myisamchk --analyze.
For more information on how the analysis works within
InnoDB, see
InnoDB Limitations.
MariaDB uses the stored key distribution to decide the order
in which
tables should be joined when you perform a join on something
other than
a constant. In addition, key distributions can be used when
deciding
which indexes to use for a specific table within a query.
This statement requires SELECT and INSERT privileges for the
table.
By default, ANALYZE TABLE statements are written to the
binary log and will be replicated. The NO_WRITE_TO_BINLOG
keyword (LOCAL is an alias) will ensure the statement is not
written to the binary log.
ANALYZE TABLE is also supported for partitioned tables. You
can use ALTER TABLE ... ANALYZE PARTITION to analyze one or
more partitions.
The Aria storage engine supports progress reporting for the
ANALYZE TABLE statement.
Engine-Independent Statistics
In MariaDB 10.0 and later, ANALYZE TABLE supports
engine-independent statistics. See Engine-Independent Table
Statistics: Collecting Statistics with the ANALYZE TABLE
Statement for more information.
URL: https://mariadb.com/kb/en/analyze-table/https://mariadb.com/kb/en/analyze-table/ � � 3 CHECK TABLESyntax
------
CHECK TABLE tbl_name [, tbl_name] ... [option] ...
option = {FOR UPGRADE | QUICK | FAST | MEDIUM | EXTENDED |
CHANGED}
Description
-----------
CHECK TABLE checks a table or tables for errors. CHECK TABLE
works for
Archive, Aria, CSV, InnoDB, and MyISAM tables. For Aria and
MyISAM tables, the
key statistics are updated as well. For CSV, see also
Checking and Repairing CSV Tables.
As an alternative, myisamchk is a commandline tool for
checking MyISAM tables when the tables are not being
accessed.
For checking dynamic columns integrity, COLUMN_CHECK() can
be used.
CHECK TABLE can also check views for problems, such as
tables
that are referenced in the view definition that no longer
exist.
CHECK TABLE is also supported for partitioned tables. You
can
use ALTER TABLE ... CHECK PARTITION
to check one or more partitions.
The meaning of the different options are as follows - note
that this can vary a bit between
storage engines:
FOR UPGRADE | Do a very quick check if the storage format
for the table has changed so that one needs to do a REPAIR.
This is only needed when one upgrades between major versions
of MariaDB or MySQL. This is usually done by running
mysql_upgrade. |
FAST | Only check tables that has not been closed properly
or are marked as corrupt. Only supported by the MyISAM and
Aria engines. For other engines the table is checked
normally |
CHANGED | Check only tables that has changed since last
REPAIR / CHECK. Only supported by the MyISAM and Aria
engines. For other engines the table is checked normally. |
QUICK | Do a fast check. For MyISAM and Aria engine this
means we skip checking the delete link chain which may take
some time. |
MEDIUM | Scan also the data files. Checks integrity between
data and index files with checksums. In most cases this
should find all possible errors. |
EXTENDED | Does a full check to verify every possible error.
For MyISAM and Aria we verify for each row that all it keys
exists and points to the row. This may take a long time on
big tables! |
For most cases running CHECK TABLE without options or MEDIUM
should be
good enough.
Since MariaDB 5.3, the Aria storage engine supports progress
reporting for this statement.
If you want to know if two tables are identical, take a look
at CHECKSUM TABLE.
XtraDB/InnoDB
If CHECK TABLE finds an error in an InnoDB table, MariaDB
might shutdown to prevent the error propagation. In this
case, the problem will be reported in the error log.
Otherwise, since MariaDB 5.5, the table or an index might be
marked as corrupted, to prevent use. This does not happen
with some minor problems, like a wrong number of entries in
a secondary index. Those problems are reported in the output
of CHECK TABLE.
Each tablespace contains a header with metadata. This header
is not checked by this statement.
During the execution of CHECK TABLE, other threads may be
blocked.
URL: https://mariadb.com/kb/en/sql-commands-check-table/https://mariadb.com/kb/en/sql-commands-check-table/ � �" TOUCHESSyntax
------
Touches(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether g1 spatially touches g2.
Two
geometries spatially touch if the interiors of the
geometries do not intersect,
but the boundary of one of the geometries intersects either
the boundary or the
interior of the other.
TOUCHES() is based on the original MySQL implementation and
uses object bounding rectangles, while ST_TOUCHES() uses
object shapes.
URL: https://mariadb.com/kb/en/touches/https://mariadb.com/kb/en/touches/ & & r � f �AR1 �Q � �) OPTIMIZE TABLESyntax
------
OPTIMIZE [NO_WRITE_TO_BINLOG | LOCAL] TABLE
tbl_name [, tbl_name] ...
[WAIT n | NOWAIT]
Description
-----------
OPTIMIZE TABLE has two main functions. It can either be used
to defragment tables, or to update the InnoDB fulltext
index.
WAIT/NOWAIT
Set the lock wait timeout. See WAIT and NOWAIT.
Defragmenting
OPTIMIZE TABLE works for InnoDB (before MariaDB 10.1.1, only
if the innodb_file_per_table server system variable is set),
Aria, MyISAM and ARCHIVE tables, and should be used if you
have deleted a large part of a table or if you have made
many changes to a table with variable-length
rows (tables that have VARCHAR, VARBINARY, BLOB, or TEXT
columns). Deleted rows are maintained in a
linked list and subsequent INSERT operations reuse old row
positions.
This statement requires SELECT and INSERT privileges for the
table.
By default, OPTIMIZE TABLE statements are written to the
binary log and will be replicated. The NO_WRITE_TO_BINLOG
keyword (LOCAL is an alias) will ensure the statement is not
written to the binary log.
OPTIMIZE TABLE is also supported for partitioned tables. You
can use
ALTER TABLE ... OPTIMIZE PARTITION
to optimize one or more partitions.
You can use OPTIMIZE TABLE to reclaim the unused
space and to defragment the data file. With other storage
engines, OPTIMIZE TABLE does nothing by default, and returns
this message: " The storage engine for the table doesn't
support optimize". However, if the server has been started
with the --skip-new option, OPTIMIZE TABLE is linked to
ALTER TABLE, and recreates the table. This operation frees
the unused space and updates index statistics.
Since MariaDB 5.3, the Aria storage engine supports progress
reporting for this statement.
If a MyISAM table is fragmented, concurrent inserts will not
be performed until an OPTIMIZE TABLE statement is executed
on that table, unless the concurrent_insert server system
variable is set to ALWAYS.
Updating an InnoDB fulltext index
When rows are added or deleted to an InnoDB fulltext index,
the index is not immediately re-organized, as this can be an
expensive operation. Change statistics are stored in a
separate location . The fulltext index is only fully
re-organized when an OPTIMIZE TABLE statement is run.
By default, an OPTIMIZE TABLE will defragment a table. In
order to use it to update fulltext index statistics, the
innodb_optimize_fulltext_only system variable must be set to
1. This is intended to be a temporary setting, and should be
reset to 0 once the fulltext index has been re-organized.
Since fulltext re-organization can take a long time, the
innodb_ft_num_word_optimize variable limits the
re-organization to a number of words (2000 by default). You
can run multiple OPTIMIZE statements to fully re-organize
the index.
Defragmenting InnoDB tablespaces
MariaDB 10.1.1 merged the Facebook/Kakao defragmentation
patch
MariaDB 10.1.1 merged the Facebook/Kakao defragmentation
patch, allowing one to use OPTIMIZE TABLE to defragment
InnoDB tablespaces. For this functionality to be enabled,
the innodb_defragment system variable must be enabled. No
new tables are created and there is no need to copy data
from old tables to new tables. Instead, this feature loads n
pages (determined by innodb-defragment-n-pages) and tries to
move records so that pages would be full of records and then
frees pages that are fully empty after the operation. Note
that tablespace files (including ibdata1) will not shrink as
the result of defragmentation, but one will get better
memory utilization in the InnoDB buffer pool as there are
fewer data pages in use.
See Defragmenting InnoDB Tablespaces for more details.
URL: https://mariadb.com/kb/en/optimize-table/https://mariadb.com/kb/en/optimize-table/ ' REPAIR TABLESyntax
------
REPAIR [NO_WRITE_TO_BINLOG | LOCAL] TABLE
tbl_name [, tbl_name] ...
[QUICK] [EXTENDED] [USE_FRM]
Description
-----------
REPAIR TABLE repairs a possibly corrupted table. By default,
it has the same effect as
myisamchk --recover tbl_name
or
aria_chk --recover tbl_name
See aria_chk and myisamchk for more.
REPAIR TABLE works for Archive, Aria, CSV and MyISAM tables.
For XtraDB/InnoDB, see recovery modes. For CSV, see also
Checking and Repairing CSV Tables. For Archive, this
statement also improves compression. If the storage engine
does not support this statement, a warning is issued.
This statement requires SELECT and INSERT privileges for the
table.
By default, REPAIR TABLE statements are written to the
binary log and will be replicated. The NO_WRITE_TO_BINLOG
keyword (LOCAL is an alias) will ensure the statement is not
written to the binary log.
When an index is recreated, the storage engine may use a
configurable buffer in the process. Incrementing the buffer
speeds up the index creation. Aria and MyISAM allocate a
buffer whose size is defined by aria_sort_buffer_size or
myisam_sort_buffer_size, also used for ALTER TABLE.
REPAIR TABLE is also supported for partitioned tables.
However, the USE_FRM option cannot be used with this
statement
on a partitioned table.
ALTER TABLE ... REPAIR PARTITION can be used
to repair one or more partitions.
The Aria storage engine supports progress reporting for this
statement.
URL: https://mariadb.com/kb/en/repair-table/https://mariadb.com/kb/en/repair-table/ � �" CURDATESyntax
------
CURDATE()
Description
-----------
Returns the current date as a value in 'YYYY-MM-DD' or
YYYYMMDD
format, depending on whether the function is used in a
string or
numeric context.
Examples
--------
SELECT CURDATE();
+------------+
| CURDATE() |
+------------+
| 2019-03-05 |
+------------+
In a numeric context (note this is not performing date
calculations):
SELECT CURDATE() +0;
+--------------+
| CURDATE() +0 |
+--------------+
| 20190305 |
+--------------+
Data calculation:
SELECT CURDATE() - INTERVAL 5 DAY;
+----------------------------+
| CURDATE() - INTERVAL 5 DAY |
+----------------------------+
| 2019-02-28 |
+----------------------------+
URL: https://mariadb.com/kb/en/curdate/https://mariadb.com/kb/en/curdate/ � � ' CURRENT_DATESyntax
------
CURRENT_DATE, CURRENT_DATE()
Description
-----------
CURRENT_DATE and CURRENT_DATE() are synonyms for CURDATE().
URL: https://mariadb.com/kb/en/current_date/https://mariadb.com/kb/en/current_date/ � � ' CURRENT_TIMESyntax
------
CURRENT_TIME
CURRENT_TIME([precision])
Description
-----------
CURRENT_TIME and CURRENT_TIME() are synonyms for CURTIME().
URL: https://mariadb.com/kb/en/current_time/https://mariadb.com/kb/en/current_time/ � � , CURRENT_TIMESTAMPSyntax
------
CURRENT_TIMESTAMP
CURRENT_TIMESTAMP([precision])
Description
-----------
CURRENT_TIMESTAMP and CURRENT_TIMESTAMP() are synonyms for
NOW().
URL: https://mariadb.com/kb/en/current_timestamp/https://mariadb.com/kb/en/current_timestamp/ � �" CURTIMESyntax
------
CURTIME([precision])
Description
-----------
Returns the current time as a value in 'HH:MM:SS' or
HHMMSS.uuuuuu format, depending on whether the function is
used in a string or numeric context. The value is expressed
in the current time zone.
The optional precision determines the microsecond precision.
See Microseconds in MariaDB.
Examples
--------
SELECT CURTIME();
+-----------+
| CURTIME() |
+-----------+
| 12:45:39 |
+-----------+
SELECT CURTIME() + 0;
+---------------+
| CURTIME() + 0 |
+---------------+
| 124545.000000 |
+---------------+
With precision:
SELECT CURTIME(2);
+-------------+
| CURTIME(2) |
+-------------+
| 09:49:08.09 |
+-------------+
URL: https://mariadb.com/kb/en/curtime/https://mariadb.com/kb/en/curtime/ vY [� Y: �D ��� �� b& REPAIR VIEWREPAIR VIEW was introduced in MariaDB 10.0.18 and MariaDB
5.5.43.
Syntax
------
REPAIR [NO_WRITE_TO_BINLOG | LOCAL] VIEW view_name[,
view_name] ... [FROM MYSQL]
Description
-----------
The REPAIR VIEW statement was introduced to assist with
fixing MDEV-6916, an issue introduced in MariaDB 5.2 where
the view algorithms were swapped compared to their MySQL on
disk representation. It checks whether the view algorithm is
correct. It is run as part of mysql_upgrade, and should not
normally be required in regular use.
By default it corrects the checksum and if necessary adds
the mariadb-version field. If the optional FROM MYSQL clause
is used, and no mariadb-version field is present, the MERGE
and TEMPTABLE algorithms are toggled.
By default, REPAIR VIEW statements are written to the binary
log and will be replicated. The NO_WRITE_TO_BINLOG keyword
(LOCAL is an alias) will ensure the statement is not written
to the binary log.
Note that REPAIR VIEW in MariaDB 10.0.18 and MariaDB 5.5.43
could crash the server (see MDEV-8115). Upgrade to a later
version.
URL: https://mariadb.com/kb/en/repair-view/https://mariadb.com/kb/en/repair-view/ u. CREATE FUNCTION UDFSyntax
------
CREATE [OR REPLACE] [AGGREGATE] FUNCTION [IF NOT EXISTS]
function_name
RETURNS {STRING|INTEGER|REAL|DECIMAL}
SONAME shared_library_name
Description
-----------
A user-defined function (UDF) is a way to extend MariaDB
with a new function
that works like a native (built-in) MariaDB function such as
ABS() or
CONCAT().
function_name is the name that should be used in SQL
statements to invoke
the function.
To create a function, you must have the INSERT privilege for
the
mysql database. This is necessary because CREATE FUNCTION
adds a row to the
mysql.func system table that records the function's name,
type, and shared library name. If you do not have this
table, you should run
the mysql_upgrade command to create it.
UDFs need to be written in C, C++ or another language that
uses C calling
conventions, MariaDB needs to have been dynamically
compiled, and your
operating system must support dynamic loading.
For an example, see sql/udf_example.cc in the source tree.
For a collection of existing UDFs see
http://www.mysqludf.org/.
Statements making use of user-defined functions are not
safe for replication.
For creating a stored function as opposed to a user-defined
function, see
CREATE FUNCTION.
For valid identifiers to use as function names, see
Identifier Names.
RETURNS
The RETURNS clause indicates the type of the function's
return value, and can be one of STRING, INTEGER, REAL or
DECIMAL. DECIMAL functions currently return string values
and should be written like STRING functions.
shared_library_name
shared_library_name is the basename of the shared object
file that contains
the code that implements the function. The file must be
located in the plugin
directory. This directory is given by the value of the
plugin_dir system variable. Note that
before MariaDB/MySQL 5.1, the shared object could be located
in any directory
that was searched by your system's dynamic linker.
AGGREGATE
Aggregate functions are summary functions such as SUM() and
AVG().
Aggregate UDF functions can be used as window functions.
OR REPLACE
The OR REPLACE clause was added in MariaDB 10.1.3
If the optional OR REPLACE clause is used, it acts as a
shortcut for:
DROP FUNCTION IF EXISTS function_name;
CREATE FUNCTION name ...;
IF NOT EXISTS
The IF NOT EXISTS clause was added in MariaDB 10.1.3
When the IF NOT EXISTS clause is used, MariaDB will return a
warning instead of an error if the specified function
already exists. Cannot be used together with OR REPLACE.
Upgrading a UDF
To upgrade the UDF's shared library, first run a
DROP FUNCTION statement, then upgrade the shared library and
finally run the CREATE FUNCTION statement. If you upgrade
without following
this process, you may crash the server.
Examples
--------
CREATE FUNCTION jsoncontains_path RETURNS integer SONAME
'ha_connect.so';
Query OK, 0 rows affected (0.00 sec)
OR REPLACE and IF NOT EXISTS:
CREATE FUNCTION jsoncontains_path RETURNS integer SONAME
'ha_connect.so';
ERROR 1125 (HY000): Function 'jsoncontains_path' already
exists
CREATE OR REPLACE FUNCTION jsoncontains_path RETURNS integer
SONAME 'ha_connect.so';
Query OK, 0 rows affected (0.00 sec)
CREATE FUNCTION IF NOT EXISTS jsoncontains_path RETURNS
integer SONAME 'ha_connect.so';
Query OK, 0 rows affected, 1 warning (0.00 sec)
SHOW WARNINGS;
+-------+------+---------------------------------------------+
| Level | Code | Message |
+-------+------+---------------------------------------------+
| Note | 1125 | Function 'jsoncontains_path' already
exists |
+-------+------+---------------------------------------------+
URL: https://mariadb.com/kb/en/create-function-udf/https://mariadb.com/kb/en/create-function-udf/ �
( DATE FUNCTIONSyntax
------
DATE(expr)
Description
-----------
Extracts the date part of the date or datetime expression
expr.
Examples
--------
SELECT DATE('2013-07-18 12:21:32');
+-----------------------------+
| DATE('2013-07-18 12:21:32') |
+-----------------------------+
| 2013-07-18 |
+-----------------------------+
Error Handling
Until MariaDB 5.5.32, some versions of MariaDB returned
0000-00-00 when passed an invalid date. From 5.5.32, NULL is
returned.
URL: https://mariadb.com/kb/en/date-function/https://mariadb.com/kb/en/date-function/ � � DAYSyntax
------
DAY(date)
Description
-----------
DAY() is a synonym for DAYOFMONTH().
URL: https://mariadb.com/kb/en/day/https://mariadb.com/kb/en/day/ � ^$ DAYOFYEARSyntax
------
DAYOFYEAR(date)
Description
-----------
Returns the day of the year for date, in the range 1 to 366.
Examples
--------
SELECT DAYOFYEAR('2018-02-16');
+-------------------------+
| DAYOFYEAR('2018-02-16') |
+-------------------------+
| 47 |
+-------------------------+
URL: https://mariadb.com/kb/en/dayofyear/https://mariadb.com/kb/en/dayofyear/ � �$ FROM_DAYSSyntax
------
FROM_DAYS(N)
Description
-----------
Given a day number N, returns a DATE value. The day count is
based on the number of days from the start of the standard
calendar (0000-00-00).
The function is not designed for use with dates before the
advent of the Gregorian calendar in October 1582. Results
will not be reliable since it doesn't account for the lost
days when the calendar changed from the Julian calendar.
This is the converse of the TO_DAYS() function.
Examples
--------
SELECT FROM_DAYS(730669);
+-------------------+
| FROM_DAYS(730669) |
+-------------------+
| 2000-07-03 |
+-------------------+
URL: https://mariadb.com/kb/en/from_days/https://mariadb.com/kb/en/from_days/ � � $ LOCALTIMESyntax
------
LOCALTIME
LOCALTIME([precision])
Description
-----------
LOCALTIME and LOCALTIME() are synonyms for NOW().
URL: https://mariadb.com/kb/en/localtime/https://mariadb.com/kb/en/localtime/ � � ) LOCALTIMESTAMPSyntax
------
LOCALTIMESTAMP
LOCALTIMESTAMP([precision])
Description
-----------
LOCALTIMESTAMP and LOCALTIMESTAMP() are synonyms for NOW().
URL: https://mariadb.com/kb/en/localtimestamp/https://mariadb.com/kb/en/localtimestamp/ �� ���� qQ�� �^+�; �� ), DROP FUNCTION UDFSyntax
------
DROP FUNCTION [IF EXISTS] function_name
Description
-----------
This statement drops the user-defined function (UDF) named
function_name.
To drop a function, you must have the DELETE privilege for
the mysql database. This is because DROP FUNCTION removes
the row from the mysql.func system table that records the
function's name, type and shared library name.
For dropping a stored function, see DROP FUNCTION.
Upgrading a UDF
To upgrade the UDF's shared library, first run a DROP
FUNCTION statement, then upgrade the shared library and
finally run the CREATE FUNCTION statement. If you upgrade
without following this process, you may crash the server.
Examples
--------
DROP FUNCTION jsoncontains_path;
IF EXISTS:
DROP FUNCTION jsoncontains_path;
ERROR 1305 (42000): FUNCTION test.jsoncontains_path does not
exist
DROP FUNCTION IF EXISTS jsoncontains_path;
Query OK, 0 rows affected, 1 warning (0.00 sec)
SHOW WARNINGS;
+-------+------+------------------------------------------------+
| Level | Code | Message |
+-------+------+------------------------------------------------+
| Note | 1305 | FUNCTION test.jsoncontains_path does not
exist |
+-------+------+------------------------------------------------+
URL: https://mariadb.com/kb/en/drop-function-udf/https://mariadb.com/kb/en/drop-function-udf/ �: Creating User-Defined FunctionsUser-defined functions allow MariaDB to be extended with a
new function that works like a native (built-in) MariaDB
function such as ABS() or CONCAT(). There are alternative
ways to add a new function: writing a native function (which
requires modifying and compiling the server source code), or
writing a stored function.
Statements making use of user-defined functions are not safe
for replication.
Functions are written in C or C++, and to make use of them,
the operating system must support dynamic loading.
Each new SQL function requires corresponding functions
written in C/C++. In the list below, at least the main
function - x() - and one other, are required. x should be
replaced by the name of the function you are creating.
All functions need to be thread-safe, so not global or
static variables that change can be allocated. Memory is
allocated in x_init()/ and freed in x_deinit().
Simple Functions
x()
Required for all UDF's, this is where the results are
calculated.
C/C++ type | SQL type |
char * | STRING |
long long | INTEGER |
double | REAL |
DECIMAL functions return string values, and so should be
written accordingly. It is not possible to create ROW
functions.
x_init()
Initialization function for x(). Can be used for the
following:
Check the number of arguments to X() (the SQL equivalent).
Verify the argument types, or to force arguments to be of a
particular type after the function is called.
Specify whether the result can be NULL.
Specify the maximum result length.
For REAL functions, specify the maximum number of decimals
for the result.
Allocate any required memory.
To verify that the arguments are of a required type or,
alternatively, to tell MySQL to coerce arguments to the
required types when the main function is called.
x_deinit()
De-initialization function for x(). Used to de-allocate
memory that was allocated in x_init().
Description
-----------
Each time the SQL function X() is called:
MariaDB will first call the C/C++ initialization function,
x_init(), assuming it exists. All setup will be performed,
and if it returns an error, the SQL statement is aborted and
no further functions are called.
If there is no x_init() function, or it has been called and
did not return an error, x() is then called once per row.
After all rows have finished processing, x_deinit() is
called, if present, to clean up by de-allocating any memory
that was allocated in x_init().
See User-defined Functions Calling Sequences for more
details on the functions.
Aggregate Functions
The following functions are required for aggregate
functions, such as AVG() and SUM().
x_clear()
Used to reset the current aggregate, but without inserting
the argument as the initial aggregate value for the new
group.
x_add()
Used to add the argument to the current aggregate.
x_remove()
Staring from MariaDB 10.4 it improves the support of window
functions (so it is not obligatory to add it) and should
remove the argument from the current aggregate.
Description
-----------
Each time the aggregate SQL function X() is called:
MariaDB will first call the C/C++ initialization function,
x_init(), assuming it exists. All setup will be performed,
and if it returns an error, the SQL statement is aborted and
no further functions are called.
If there is no x_init() function, or it has been called and
did not return an error, x() is then called once per row.
After all rows have finished processing, x_deinit() is
called, if present, to clean up by de-allocating any memory
that was allocated in x_init().
MariaDB will first call the C/C++ initialization function,
x_init(), assuming it exists. All setup will be performed,
and if it returns an error, the SQL statement is aborted and
no further functions are called.
The table is sorted according to the GROUP BY expression.
x_clear() is called for the first row of each new group.
x_add() is called once per row for each row in the same
group.
x() is called when the group changes, or after the last row,
to get the aggregate result.
The latter three steps are repeated until all rows have been
processed.
After all rows have finished processing, x_deinit() is
called, if present, to clean up by de-allocating any memory
that was allocated in x_init().
Examples
--------
For an example, see sql/udf_example.cc in the source tree.
For a collection of existing UDFs see
https://github.com/mysqludf.
URL:
https://mariadb.com/kb/en/creating-user-defined-functions/https://mariadb.com/kb/en/creating-user-defined-functions/ � �! MINUTESyntax
------
MINUTE(time)
Description
-----------
Returns the minute for time, in the range 0 to 59.
Examples
--------
SELECT MINUTE('2013-08-03 11:04:03');
+-------------------------------+
| MINUTE('2013-08-03 11:04:03') |
+-------------------------------+
| 4 |
+-------------------------------+
SELECT MINUTE ('23:12:50');
+---------------------+
| MINUTE ('23:12:50') |
+---------------------+
| 12 |
+---------------------+
URL: https://mariadb.com/kb/en/minute/https://mariadb.com/kb/en/minute/ � " MONTHSyntax
------
MONTH(date)
Description
-----------
Returns the month for date in the range 1 to 12 for January
to
December, or 0 for dates such as '0000-00-00' or
'2008-00-00' that
have a zero month part.
Examples
--------
SELECT MONTH('2019-01-03');
+---------------------+
| MONTH('2019-01-03') |
+---------------------+
| 1 |
+---------------------+
SELECT MONTH('2019-00-03');
+---------------------+
| MONTH('2019-00-03') |
+---------------------+
| 0 |
+---------------------+
URL: https://mariadb.com/kb/en/month/https://mariadb.com/kb/en/month/ � �$ MONTHNAMESyntax
------
MONTHNAME(date)
Description
-----------
Returns the full name of the month for date. The language
used for the name is controlled by the value of the
lc_time_names system variable. See server locale for more on
the supported locales.
Examples
--------
SELECT MONTHNAME('2019-02-03');
+-------------------------+
| MONTHNAME('2019-02-03') |
+-------------------------+
| February |
+-------------------------+
Changing the locale:
SET lc_time_names = 'fr_CA';
SELECT MONTHNAME('2019-05-21');
+-------------------------+
| MONTHNAME('2019-05-21') |
+-------------------------+
| mai |
+-------------------------+
URL: https://mariadb.com/kb/en/monthname/https://mariadb.com/kb/en/monthname/ ���Uy'�� t� �� (PC User-Defined Functions Calling SequencesThe functions described in Creating User-defined Functions
are expanded on this page. They are declared as follows:
Simple Functions
x()
If x() returns an integer, it is declared as follows:
long long x(UDF_INIT *initid, UDF_ARGS *args,
char *is_null, char *error);
If x() returns a string (DECIMAL functions also return
string values), it is declared as follows:
char *x(UDF_INIT *initid, UDF_ARGS *args,
char *result, unsigned long *length,
char *is_null, char *error);
If x() returns a real, it is declared as follows:
double x(UDF_INIT *initid, UDF_ARGS *args,
char *is_null, char *error);
x_init()
my_bool x_init(UDF_INIT *initid, UDF_ARGS *args, char
*message);
x_deinit()
void x_deinit(UDF_INIT *initid);
Description
-----------
initid is a parameter passed to all three functions that
points to a UDF_INIT structure, used for communicating
information between the functions. Its structure members
are:
my_bool maybe_null
maybe_null should be set to 1 if x_init can return a NULL
value, Defaults to 1 if any arguments are declared
maybe_null.
unsigned int decimals
Number of decimals after the decimal point. The default, if
an explicit number of decimals is passed in the arguments to
the main function, is the maximum number of decimals, so if
9.5, 9.55 and 9.555 are passed to the function, the default
would be three (based on 9.555, the maximum). If there are
no explicit number of decimals, the default is set to 31, or
one more than the maximum for the DOUBLE, FLOAT and DECIMAL
types. This default can be changed in the function to suit
the actual calculation.
unsigned int max_length
Maximum length of the result. For integers, the default is
21. For strings, the length of the longest argument. For
reals, the default is 13 plus the number of decimals
indicated by initid->decimals. The length includes any signs
or decimal points. Can also be set to 65KB or 16MB in order
to return a BLOB. The memory remains unallocated, but this
is used to decide on the data type to use if the data needs
to be temporarily stored.
char *ptr
A pointer for use as required by the function. Commonly,
initid->ptr is used to communicate allocated memory, with
x_init() allocating the memory and assigning it to this
pointer, x() using it, and x_deinit() de-allocating it.
my_bool const_item
Should be set to 1 in x_init() if x() always returns the
same value, otherwise 0.
Aggregate Functions
x_clear()
x_clear() is a required function for aggregate functions,
and is declared as follows:
void x_clear(UDF_INIT *initid, char *is_null, char *error);
It is called when the summary results need to be reset, that
is at the beginning of each new group. but also to reset the
values when there were no matching rows.
is_null is set to point to CHAR(0) before calling x_clear().
In the case of an error, you can store the value to which
the error argument points (a single-byte variable, not a
string string buffer) in the variable.
x_reset()
x_reset() is declared as follows:
void x_reset(UDF_INIT *initid, UDF_ARGS *args,
char *is_null, char *error);
It is called on finding the first row in a new group. Should
reset the summary variables, and then use UDF_ARGS as the
first value in the group's internal summary value. The
function is not required if the UDF interface uses
x_clear().
x_add()
x_add() is declared as follows:
void x_add(UDF_INIT *initid, UDF_ARGS *args,
char *is_null, char *error);
It is called for all rows belonging to the same group, and
should be used to add the value in UDF_ARGS to the internal
summary variable.
x_remove()
x_remove() was added in MariaDB 10.4 and is declared as
follows (same as x_add()):
void x_remove(UDF_INIT* initid, UDF_ARGS* args,
char* is_null, char *error );
It adds more efficient support of aggregate UDFs as window
functions. x_remove() should "subtract" the row (reverse
x_add()). In MariaDB 10.4 aggregate UDFs will work as WINDOW
functions without x_remove() but it will not be so
efficient.
If x_remove() supported (defined) detected automatically.
URL:
https://mariadb.com/kb/en/user-defined-functions-calling-sequences/https://mariadb.com/kb/en/user-defined-functions-calling-sequences/ : User-Defined Functions SecurityThe MariaDB server imposes a number of limitations on
user-defined functions for security purposes.
The INSERT privilege for the mysql database is required to
run CREATE FUNCTION, as a record will be added to the
mysql.func-table.
The DELETE privilege for the mysql database is required to
run DROP FUNCTION as the corresponding record will be
removed from the mysql.func-table.
UDF object files can only be placed in the plugin directory,
as specified by the value of the plugin_dir system variable.
At least one symbol, beyond the required x() - corresponding
to an SQL function X()) - is required. These can be
x_init(), x_deinit(), xxx_reset(), x_clear() and x_add()
functions (see Creating User-defined Functions). The
allow-suspicious-udfs mysqld option (by default unset)
provides a workaround, permitting only one symbol to be
used. This is not recommended, as it opens the possibility
of loading shared objects that are not legitimate
user-defined functions.
URL:
https://mariadb.com/kb/en/user-defined-functions-security/https://mariadb.com/kb/en/user-defined-functions-security/ � ^" QUARTERSyntax
------
QUARTER(date)
Description
-----------
Returns the quarter of the year for date, in the range 1 to
4. Returns 0 if month contains a zero value, or NULL if the
given value is not otherwise a valid date (zero values are
accepted).
Examples
--------
SELECT QUARTER('2008-04-01');
+-----------------------+
| QUARTER('2008-04-01') |
+-----------------------+
| 2 |
+-----------------------+
SELECT QUARTER('2019-00-01');
+-----------------------+
| QUARTER('2019-00-01') |
+-----------------------+
| 0 |
+-----------------------+
URL: https://mariadb.com/kb/en/quarter/https://mariadb.com/kb/en/quarter/ � (! SECONDSyntax
------
SECOND(time)
Description
-----------
Returns the second for a given time (which can include
microseconds), in the range 0 to 59, or NULL if not given a
valid time value.
Examples
--------
SELECT SECOND('10:05:03');
+--------------------+
| SECOND('10:05:03') |
+--------------------+
| 3 |
+--------------------+
SELECT SECOND('10:05:01.999999');
+---------------------------+
| SECOND('10:05:01.999999') |
+---------------------------+
| 1 |
+---------------------------+
URL: https://mariadb.com/kb/en/second/https://mariadb.com/kb/en/second/ �
r( TIME FunctionSyntax
------
TIME(expr)
Description
-----------
Extracts the time part of the time or datetime expression
expr and
returns it as a string.
Examples
--------
SELECT TIME('2003-12-31 01:02:03');
+-----------------------------+
| TIME('2003-12-31 01:02:03') |
+-----------------------------+
| 01:02:03 |
+-----------------------------+
SELECT TIME('2003-12-31 01:02:03.000123');
+------------------------------------+
| TIME('2003-12-31 01:02:03.000123') |
+------------------------------------+
| 01:02:03.000123 |
+------------------------------------+
URL: https://mariadb.com/kb/en/time-function/https://mariadb.com/kb/en/time-function/ G��]U��� �PD� �Q * mysql.func TableThe mysql.func table stores information about user-defined
functions (UDFs) created with the CREATE FUNCTION UDF
statement.
In MariaDB 10.4 and later, this table uses the Aria storage
engine.
MariaDB until 10.3
In MariaDB 10.3 and before, this table uses the MyISAM
storage engine.
The mysql.func table contains the following fields:
Field | Type | Null | Key | Default | Description |
name | char(64) | NO | PRI | | UDF name |
ret | tinyint(1) | NO | | 0 | |
dl | char(128) | NO | | | Shared library name |
type | enum('function','aggregate') | NO | | NULL |
Type, either function or aggregate. Aggregate functions are
summary functions such as SUM() and AVG(). |
Example
SELECT * FROM mysql.func;
+------------------------------+-----+--------------+-----------+
| name | ret | dl | type |
+------------------------------+-----+--------------+-----------+
| spider_direct_sql | 2 | ha_spider.so | function |
| spider_bg_direct_sql | 2 | ha_spider.so | aggregate |
| spider_ping_table | 2 | ha_spider.so | function |
| spider_copy_tables | 2 | ha_spider.so | function |
| spider_flush_table_mon_cache | 2 | ha_spider.so | function
|
+------------------------------+-----+--------------+-----------+
URL: https://mariadb.com/kb/en/mysqlfunc-table/https://mariadb.com/kb/en/mysqlfunc-table/ �) AUTO_INCREMENTDescription
-----------
The AUTO_INCREMENT attribute can be used to generate a
unique identity for new rows. When you insert a new record
to the table, and the auto_increment field is NULL or
DEFAULT, the value will automatically be incremented. This
also applies to 0, unless the NO_AUTO_VALUE_ON_ZERO SQL_MODE
is enabled.
AUTO_INCREMENT columns start from 1 by default. The
automatically generated value can never be lower than 0.
Each table can have only one AUTO_INCREMENT column. It must
defined as a key (not necessarily the PRIMARY KEY or UNIQUE
key). In some storage engines (including the default
InnoDB), if the key consists of multiple columns, the
AUTO_INCREMENT column must be the first column. Storage
engines that permit the column to be placed elsewhere are
Aria, MyISAM, MERGE, Spider, TokuDB, BLACKHOLE, FederatedX
and Federated.
CREATE TABLE animals (
id MEDIUMINT NOT NULL AUTO_INCREMENT,
name CHAR(30) NOT NULL,
PRIMARY KEY (id)
);
INSERT INTO animals (name) VALUES
('dog'),('cat'),('penguin'),
('fox'),('whale'),('ostrich');
SELECT * FROM animals;
+----+---------+
| id | name |
+----+---------+
| 1 | dog |
| 2 | cat |
| 3 | penguin |
| 4 | fox |
| 5 | whale |
| 6 | ostrich |
+----+---------+
SERIAL is an alias for BIGINT UNSIGNED NOT NULL
AUTO_INCREMENT UNIQUE.
CREATE TABLE t (id SERIAL, c CHAR(1)) ENGINE=InnoDB;
SHOW CREATE TABLE t \G
*************************** 1. row
***************************
Table: t
Create Table: CREATE TABLE `t` (
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`c` char(1) DEFAULT NULL,
UNIQUE KEY `id` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
Setting or Changing the Auto_Increment Value
You can use an ALTER TABLE statement to assign a new value
to the auto_increment table option, or set the insert_id
server system variable to change the next AUTO_INCREMENT
value inserted by the current session.
LAST_INSERT_ID() can be used to see the last AUTO_INCREMENT
value inserted by the current session.
ALTER TABLE animals AUTO_INCREMENT=8;
INSERT INTO animals (name) VALUES ('aardvark');
SELECT * FROM animals;
+----+-----------+
| id | name |
+----+-----------+
| 1 | dog |
| 2 | cat |
| 3 | penguin |
| 4 | fox |
| 5 | whale |
| 6 | ostrich |
| 8 | aardvark |
+----+-----------+
SET insert_id=12;
INSERT INTO animals (name) VALUES ('gorilla');
SELECT * FROM animals;
+----+-----------+
| id | name |
+----+-----------+
| 1 | dog |
| 2 | cat |
| 3 | penguin |
| 4 | fox |
| 5 | whale |
| 6 | ostrich |
| 8 | aardvark |
| 12 | gorilla |
+----+-----------+
InnoDB/XtraDB
Until MariaDB 10.2.3, InnoDB and XtraDB used an
auto-increment counter that is stored in memory. When the
server restarts, the counter is re-initialized to the
highest value used in the table, which cancels the effects
of any AUTO_INCREMENT = N option in the table statements.
From MariaDB 10.2.4, this restriction has been lifted and
AUTO_INCREMENT is persistent.
See also AUTO_INCREMENT Handling in XtraDB/InnoDB.
Setting Explicit Values
It is possible to specify a value for an AUTO_INCREMENT
column. The value must not exist in the key.
If the new value is higher than the current maximum value,
the AUTO_INCREMENT value is updated, so the next value will
be higher. If the new value is lower than the current
maximum value, the AUTO_INCREMENT value remains unchanged.
The following example demonstrates these behaviours:
CREATE TABLE t (id INTEGER UNSIGNED AUTO_INCREMENT PRIMARY
KEY) ENGINE = InnoDB;
INSERT INTO t VALUES (NULL);
SELECT id FROM t;
+----+
| id |
+----+
| 1 |
+----+
INSERT INTO t VALUES (10); -- higher value
SELECT id FROM t;
+----+
| id |
+----+
| 1 |
| 10 |
+----+
INSERT INTO t VALUES (2); -- lower value
INSERT INTO t VALUES (NULL); -- auto value
SELECT id FROM t;
+----+
| id |
+----+
| 1 |
| 2 |
| 10 |
| 11 |
+----+
The ARCHIVE storage engine does not allow to insert a value
that is lower than the current maximum.
Missing Values
An AUTO_INCREMENT column normally has missing values. This
happens because if a row is deleted, or an AUTO_INCREMENT
value is explicitly updated, old values are never re-used.
The REPLACE statement also deletes a row, and its value is
wasted. With InnoDB, values can be reserved by a
transaction; but if the transaction fails (for example,
because of a ROLLBACK) the reserved value will be lost.
Thus AUTO_INCREMENT values can be used to sort results in a
chronological order, but not to create a numeric sequence.
Replication
To make master-master or Galera safe to use AUTO_INCREMENT
one should use the system variables
auto_increment_increment and auto_increment_offset to
generate unique values for each server.
CHECK Constraints, DEFAULT Values and Virtual Columns
From MariaDB 10.2.6 auto_increment columns are no longer
permitted in CHECK constraints, DEFAULT value expressions
and virtual columns. They were permitted in earlier
versions, but did not work correctly. See MDEV-11117.
URL: https://mariadb.com/kb/en/auto_increment/https://mariadb.com/kb/en/auto_increment/ L& TIME_FORMATSyntax
------
TIME_FORMAT(time,format)
Description
-----------
This is used like the DATE_FORMAT() function, but the format
string
may contain format specifiers only for hours, minutes, and
seconds.
Other specifiers produce a NULL value or 0.
Examples
--------
SELECT TIME_FORMAT('100:00:00', '%H %k %h %I %l');
+--------------------------------------------+
| TIME_FORMAT('100:00:00', '%H %k %h %I %l') |
+--------------------------------------------+
| 100 100 04 04 4 |
+--------------------------------------------+
URL: https://mariadb.com/kb/en/time_format/https://mariadb.com/kb/en/time_format/ ~& TIME_TO_SECSyntax
------
TIME_TO_SEC(time)
Description
-----------
Returns the time argument, converted to seconds.
The value returned by TIME_TO_SEC is of type DOUBLE. Before
MariaDB 5.3 (and MySQL 5.6), the type was INT. See
Microseconds in MariaDB.
Examples
--------
SELECT TIME_TO_SEC('22:23:00');
+-------------------------+
| TIME_TO_SEC('22:23:00') |
+-------------------------+
| 80580 |
+-------------------------+
SELECT TIME_TO_SEC('00:39:38');
+-------------------------+
| TIME_TO_SEC('00:39:38') |
+-------------------------+
| 2378 |
+-------------------------+
URL: https://mariadb.com/kb/en/time_to_sec/https://mariadb.com/kb/en/time_to_sec/ ��S�f� Z�G�� �� �! BIGINTSyntax
------
BIGINT[(M)] [SIGNED | UNSIGNED | ZEROFILL]
Description
-----------
A large integer. The signed range is -9223372036854775808 to
9223372036854775807. The unsigned range is 0 to
18446744073709551615.
If a column has been set to ZEROFILL, all values will be
prepended by zeros so that the BIGINT value contains a
number of M digits.
Note: If the ZEROFILL attribute has been specified, the
column will automatically become UNSIGNED.
For more details on the attributes, see Numeric Data Type
Overview.
SERIAL is an alias for:
BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE
Examples
--------
CREATE TABLE bigints (a BIGINT,b BIGINT UNSIGNED,c BIGINT
ZEROFILL);
INSERT INTO bigints VALUES (-10,-10,-10);
Query OK, 1 row affected, 2 warnings (0.08 sec)
Warning (Code 1264): Out of range value for column 'b' at
row 1
Warning (Code 1264): Out of range value for column 'c' at
row 1
INSERT INTO bigints VALUES (-10,10,-10);Query OK, 1 row
affected, 1 warning (0.08 sec)
Warning (Code 1264): Out of range value for column 'c' at
row 1
INSERT INTO bigints VALUES (-10,10,10);
INSERT INTO bigints VALUES
(9223372036854775808,9223372036854775808,9223372036854775808);
Query OK, 1 row affected, 1 warning (0.07 sec)
Warning (Code 1264): Out of range value for column 'a' at
row 1
INSERT INTO bigints VALUES
(9223372036854775807,9223372036854775808,9223372036854775808);
SELECT * FROM bigints;
+---------------------+---------------------+----------------------+
| a | b | c |
+---------------------+---------------------+----------------------+
| -10 | 0 | 00000000000000000000 |
| -10 | 10 | 00000000000000000000 |
| -10 | 10 | 00000000000000000010 |
| 9223372036854775807 | 9223372036854775808 |
09223372036854775808 |
| 9223372036854775807 | 9223372036854775808 |
09223372036854775808 |
+---------------------+---------------------+----------------------+
URL: https://mariadb.com/kb/en/bigint/https://mariadb.com/kb/en/bigint/
�! BINARYSyntax
------
BINARY(M)
Description
-----------
The BINARY type is similar to the CHAR type, but stores
binary
byte strings rather than non-binary character strings. M
represents the
column length in bytes.
It contains no character set, and comparison and sorting are
based on the numeric value of the bytes.
If the maximum length is exceeded, and SQL strict mode is
not enabled , the extra characters will be dropped with a
warning. If strict mode is enabled, an error will occur.
BINARY values are right-padded with 0x00 (the zero byte) to
the specified length when inserted. The padding is not
removed on select, so this needs to be taken into account
when sorting and comparing, where all bytes are significant.
The zero byte, 0x00 is less than a space for comparison
purposes.
Examples
--------
Inserting too many characters, first with strict mode off,
then with it on:
CREATE TABLE bins (a BINARY(10));
INSERT INTO bins VALUES('12345678901');
Query OK, 1 row affected, 1 warning (0.04 sec)
SELECT * FROM bins;
+------------+
| a |
+------------+
| 1234567890 |
+------------+
SET sql_mode='STRICT_ALL_TABLES';
INSERT INTO bins VALUES('12345678901');
ERROR 1406 (22001): Data too long for column 'a' at row 1
Sorting is performed with the byte value:
TRUNCATE bins;
INSERT INTO bins VALUES('A'),('B'),('a'),('b');
SELECT * FROM bins ORDER BY a;
+------+
| a |
+------+
| A |
| B |
| a |
| b |
+------+
Using CAST to sort as a CHAR instead:
SELECT * FROM bins ORDER BY CAST(a AS CHAR);
+------+
| a |
+------+
| a |
| A |
| b |
| B |
+------+
The field is a BINARY(10), so padding of two '\0's are
inserted, causing comparisons that don't take this into
account to fail:
TRUNCATE bins;
INSERT INTO bins VALUES('12345678');
SELECT a = '12345678', a = '12345678\0\0' from bins;
+----------------+--------------------+
| a = '12345678' | a = '12345678\0\0' |
+----------------+--------------------+
| 0 | 1 |
+----------------+--------------------+
URL: https://mariadb.com/kb/en/binary/https://mariadb.com/kb/en/binary/ y BITSyntax
------
BIT[(M)]
Description
-----------
A bit-field type. M indicates the number of bits per value,
from 1 to
64. The default is 1 if M is omitted.
Bit values can be inserted with b'value' notation, where
value is the bit value in 0's and 1's.
Bit fields are automatically zero-padded from the left to
the full length of the bit, so for example in a BIT(4)
field, '10' is equivalent to '0010'.
Bits are returned as binary, so to display them, either add
0, or use a function such as HEX, OCT or BIN to convert
them.
Examples
--------
CREATE TEMPORARY TABLE b ( b1 BIT(8) );
INSERT INTO b VALUES
(b'11111111'),(b'01010101'),(b'1111111111111');
Query OK, 3 rows affected, 1 warning (0.10 sec)
Records: 3 Duplicates: 0 Warnings: 1
SHOW WARNINGS;
+---------+------+---------------------------------------------+
| Level | Code | Message |
+---------+------+---------------------------------------------+
| Warning | 1264 | Out of range value for column 'b1' at
row 3 |
+---------+------+---------------------------------------------+
SELECT b1+0, HEX(b1), OCT(b1), BIN(b1) FROM b;
+------+---------+---------+----------+
| b1+0 | HEX(b1) | OCT(b1) | BIN(b1) |
+------+---------+---------+----------+
| 255 | FF | 377 | 11111111 |
| 85 | 55 | 125 | 1010101 |
| 255 | FF | 377 | 11111111 |
+------+---------+---------+----------+
URL: https://mariadb.com/kb/en/bit/https://mariadb.com/kb/en/bit/ �# UTC_DATESyntax
------
UTC_DATE, UTC_DATE()
Description
-----------
Returns the current UTC date as a value in 'YYYY-MM-DD' or
YYYYMMDD
format, depending on whether the function is used in a
string or numeric context.
Examples
--------
SELECT UTC_DATE(), UTC_DATE() + 0;
+------------+----------------+
| UTC_DATE() | UTC_DATE() + 0 |
+------------+----------------+
| 2010-03-27 | 20100327 |
+------------+----------------+
URL: https://mariadb.com/kb/en/utc_date/https://mariadb.com/kb/en/utc_date/
�# UTC_TIMESyntax
------
UTC_TIME
UTC_TIME([precision])
Description
-----------
Returns the current UTC time as a value in 'HH:MM:SS' or
HHMMSS.uuuuuu format, depending on whether the function is
used in a string or numeric context.
The optional precision determines the microsecond precision.
See Microseconds in MariaDB.
Examples
--------
SELECT UTC_TIME(), UTC_TIME() + 0;
+------------+----------------+
| UTC_TIME() | UTC_TIME() + 0 |
+------------+----------------+
| 17:32:34 | 173234.000000 |
+------------+----------------+
With precision:
SELECT UTC_TIME(5);
+----------------+
| UTC_TIME(5) |
+----------------+
| 07:52:50.78369 |
+----------------+
URL: https://mariadb.com/kb/en/utc_time/https://mariadb.com/kb/en/utc_time/ [ ' AsBinaryA synonym for ST_AsBinary().
URL: https://mariadb.com/kb/en/wkb-asbinary/https://mariadb.com/kb/en/wkb-asbinary/ T AsWKBA synonym for ST_AsBinary().
URL: https://mariadb.com/kb/en/aswkb/https://mariadb.com/kb/en/aswkb/ �' MLineFromWKBSyntax
------
MLineFromWKB(wkb[,srid])
MultiLineStringFromWKB(wkb[,srid])
Description
-----------
Constructs a MULTILINESTRING value using its WKB
representation and SRID.
MLineFromWKB() and MultiLineStringFromWKB() are synonyms.
Examples
--------
SET @g = ST_AsBinary(MLineFromText('MULTILINESTRING((10
48,10 21,10 0),(16 0,16 23,16 48))'));
SELECT ST_AsText(MLineFromWKB(@g));
+--------------------------------------------------------+
| ST_AsText(MLineFromWKB(@g)) |
+--------------------------------------------------------+
| MULTILINESTRING((10 48,10 21,10 0),(16 0,16 23,16 48)) |
+--------------------------------------------------------+
URL: https://mariadb.com/kb/en/mlinefromwkb/https://mariadb.com/kb/en/mlinefromwkb/ �U� �� ��� ���/ ����
�� � BLOBSyntax
------
BLOB[(M)]
Description
-----------
A BLOB column with a maximum length of 65,535 (216 - 1)
bytes. Each
BLOB value is stored using a two-byte length prefix that
indicates the
number of bytes in the value.
An optional length M can be given for this type. If this is
done,
MariaDB creates the column as the smallest BLOB type large
enough to
hold values M bytes long.
BLOBS can also be used to store dynamic columns.
Before MariaDB 10.2.1, BLOB and TEXT columns could not be
assigned a DEFAULT value. This restriction was lifted in
MariaDB 10.2.1.
Indexing
In MariaDB 10.4, it is possible to set a Unique index on a
column that uses the BLOB data type. In previous releases
this was not possible, as the index would only guarantee the
uniqueness of a fixed number of characters.
Oracle Mode
In Oracle mode from MariaDB 10.3, BLOB is a synonym for
LONGBLOB.
URL: https://mariadb.com/kb/en/blob/https://mariadb.com/kb/en/blob/ �" BOOLEANSyntax
------
BOOL, BOOLEAN
Description
-----------
These types are synonyms for TINYINT(1).
A value of zero is considered false. Non-zero values are
considered true:
mysql> SELECT IF(0, 'true', 'false');
+------------------------+
| IF(0, 'true', 'false') |
+------------------------+
| false |
+------------------------+
mysql> SELECT IF(1, 'true', 'false');
+------------------------+
| IF(1, 'true', 'false') |
+------------------------+
| true |
+------------------------+
mysql> SELECT IF(2, 'true', 'false');
+------------------------+
| IF(2, 'true', 'false') |
+------------------------+
| true |
+------------------------+
However, the values TRUE and FALSE are merely aliases for 1
and 0,
respectively, as shown here:
mysql> SELECT IF(0 = FALSE, 'true', 'false');
+--------------------------------+
| IF(0 = FALSE, 'true', 'false') |
+--------------------------------+
| true |
+--------------------------------+
mysql> SELECT IF(1 = TRUE, 'true', 'false');
+-------------------------------+
| IF(1 = TRUE, 'true', 'false') |
+-------------------------------+
| true |
+-------------------------------+
mysql> SELECT IF(2 = TRUE, 'true', 'false');
+-------------------------------+
| IF(2 = TRUE, 'true', 'false') |
+-------------------------------+
| false |
+-------------------------------+
mysql> SELECT IF(2 = FALSE, 'true', 'false');
+--------------------------------+
| IF(2 = FALSE, 'true', 'false') |
+--------------------------------+
| false |
+--------------------------------+
UNKNOWN is an alias for NULL.
The last two statements display the results shown because 2
is equal
to neither 1 nor 0.
URL: https://mariadb.com/kb/en/boolean/https://mariadb.com/kb/en/boolean/ c CHARThis article covers the CHAR data type. See CHAR Function
for the function.
Syntax
------
[NATIONAL] CHAR[(M)] [CHARACTER SET charset_name] [COLLATE
collation_name]
Description
-----------
A fixed-length string that is always right-padded with
spaces to the specified
length when stored. M represents the column length in
characters. The range
of M is 0 to 255. If M is omitted, the length is 1.
CHAR(0) columns can contain 2 values: an empty string or
NULL. Such columns cannot be part of an index. The CONNECT
storage engine does not support CHAR(0).
Note: Trailing spaces are removed when CHAR values are
retrieved
unless the PAD_CHAR_TO_FULL_LENGTH SQL mode is enabled.
Before MariaDB 10.2, all collations were of type PADSPACE,
meaning that CHAR (as well as VARCHAR and TEXT) values are
compared without regard for trailing spaces. This does not
apply to the LIKE pattern-matching operator, which takes
into account trailing spaces.
If a unique index consists of a column where trailing pad
characters are stripped or ignored, inserts into that column
where values differ only by the number of trailing pad
characters will result in a duplicate-key error.
Examples
--------
Trailing spaces:
CREATE TABLE strtest (c CHAR(10));
INSERT INTO strtest VALUES('Maria ');
SELECT c='Maria',c='Maria ' FROM strtest;
+-----------+--------------+
| c='Maria' | c='Maria ' |
+-----------+--------------+
| 1 | 1 |
+-----------+--------------+
SELECT c LIKE 'Maria',c LIKE 'Maria ' FROM strtest;
+----------------+-------------------+
| c LIKE 'Maria' | c LIKE 'Maria ' |
+----------------+-------------------+
| 1 | 0 |
+----------------+-------------------+
NO PAD Collations
NO PAD collations regard trailing spaces as normal
characters. You can get a list of all NO PAD collations by
querying the Information Schema Collations table, for
example:
SELECT collation_name FROM information_schema.collations
WHERE collation_name LIKE "%nopad%";
+------------------------------+
| collation_name |
+------------------------------+
| big5_chinese_nopad_ci |
| big5_nopad_bin |
...
URL: https://mariadb.com/kb/en/char/https://mariadb.com/kb/en/char/
�( MPointFromWKBSyntax
------
MPointFromWKB(wkb[,srid])
MultiPointFromWKB(wkb[,srid])
Description
-----------
Constructs a MULTIPOINT value using its WKB representation
and SRID.
MPointFromWKB() and MultiPointFromWKB() are synonyms.
Examples
--------
SET @g = ST_AsBinary(MPointFromText('MultiPoint( 1 1, 2 2,
5 3, 7 2, 9 3, 8 4, 6 6, 6 9, 4 9, 1 5 )'));
SELECT ST_AsText(MPointFromWKB(@g));
+-----------------------------------------------------+
| ST_AsText(MPointFromWKB(@g)) |
+-----------------------------------------------------+
| MULTIPOINT(1 1,2 2,5 3,7 2,9 3,8 4,6 6,6 9,4 9,1 5) |
+-----------------------------------------------------+
URL: https://mariadb.com/kb/en/mpointfromwkb/https://mariadb.com/kb/en/mpointfromwkb/ g . GeomCollFromWKBA synonym for ST_GeomCollFromWKB.
URL: https://mariadb.com/kb/en/wkb-geomcollfromwkb/https://mariadb.com/kb/en/wkb-geomcollfromwkb/ m 4 GeometryCollectionFromWKBA synonym for ST_GeomCollFromWKB.
URL: https://mariadb.com/kb/en/geometrycollectionfromwkb/https://mariadb.com/kb/en/geometrycollectionfromwkb/ _ * GeometryFromWKBA synonym for ST_GeomFromWKB.
URL: https://mariadb.com/kb/en/geometryfromwkb/https://mariadb.com/kb/en/geometryfromwkb/ _ * GeomFromWKBA synonym for ST_GeomFromWKB.
URL: https://mariadb.com/kb/en/wkb-geomfromwkb/https://mariadb.com/kb/en/wkb-geomfromwkb/ _ * LineFromWKBA synonym for ST_LineFromWKB.
URL: https://mariadb.com/kb/en/wkb-linefromwkb/https://mariadb.com/kb/en/wkb-linefromwkb/ a , LineStringFromWKBA synonym for ST_LineFromWKB.
URL: https://mariadb.com/kb/en/linestringfromwkb/https://mariadb.com/kb/en/linestringfromwkb/ f 1 MultiLineStringFromWKBA synonym for MLineFromWKB().
URL: https://mariadb.com/kb/en/multilinestringfromwkb/https://mariadb.com/kb/en/multilinestringfromwkb/ ` , MultiPointFromWKBA synonym for MPointFromWKB.
URL: https://mariadb.com/kb/en/multipointfromwkb/https://mariadb.com/kb/en/multipointfromwkb/ _ . MultiPolygonFromWKBSynonym for MPolyFromWKB.
URL: https://mariadb.com/kb/en/multipolygonfromwkb/https://mariadb.com/kb/en/multipolygonfromwkb/ a + PointFromWKBA synonym for ST_PointFromWKB.
URL: https://mariadb.com/kb/en/wkb-pointfromwkb/https://mariadb.com/kb/en/wkb-pointfromwkb/ i � �� � U� �� � e� �� �� E� ?�
��� ��(�N �� � DATESyntax
------
DATE
Description
-----------
A date. The supported range is '1000-01-01' to
'9999-12-31'. MariaDB
displays DATE values in 'YYYY-MM-DD' format, but can be
assigned dates in looser formats, including strings or
numbers, as long as they make sense. These include a short
year, YY-MM-DD, no delimiters, YYMMDD, or any other
acceptable delimiter, for example YYYY/MM/DD. For details,
see date and time literals.
'0000-00-00' is a permitted special value (zero-date),
unless the NO_ZERO_DATE SQL_MODE is used. Also, individual
components of a date can be set to 0 (for example:
'2015-00-12'), unless the NO_ZERO_IN_DATE SQL_MODE is
used. In many cases, the result of en expression involving a
zero-date, or a date with zero-parts, is NULL. If the
ALLOW_INVALID_DATES SQL_MODE is enabled, if the day part is
in the range between 1 and 31, the date does not produce any
error, even for months that have less than 31 days.
Examples
--------
CREATE TABLE t1 (d DATE);
INSERT INTO t1 VALUES ("2010-01-12"), ("2011-2-28"),
('120314'),('13*04*21');
SELECT * FROM t1;
+------------+
| d |
+------------+
| 2010-01-12 |
| 2011-02-28 |
| 2012-03-14 |
| 2013-04-21 |
+------------+
URL: https://mariadb.com/kb/en/date/https://mariadb.com/kb/en/date/ �# DATETIMESyntax
------
DATETIME [(microsecond precision)]
Description
-----------
A date and time combination. The supported range is
'1000-01-01 00:00:00.000000' to '9999-12-31
23:59:59.999999'.
MariaDB displays DATETIME values in 'YYYY-MM-DD HH:MM:SS'
format, but
allows assignment of values to DATETIME columns using either
strings or
numbers. For details, see date and time literals.
The microsecond precision can be from 0-6. If not specified
0 is used.
'0000-00-00' is a permitted special value (zero-date),
unless the NO_ZERO_DATE SQL_MODE is used. Also, individual
components of a date can be set to 0 (for example:
'2015-00-12'), unless the NO_ZERO_IN_DATE SQL_MODE is
used. In many cases, the result of en expression involving a
zero-date, or a date with zero-parts, is NULL. If the
ALLOW_INVALID_DATES SQL_MODE is enabled, if the day part is
in the range between 1 and 31, the date does not produce any
error, even for months that have less than 31 days.
Since MariaDB 10.0.1, DATETIME columns also accept
CURRENT_TIMESTAMP as the default value.
MariaDB 10.1.2 introduced the --mysql56-temporal-format
option, on by default, which allows MariaDB to store
DATETMEs using the same low-level format MySQL 5.6 uses. For
more information, see Internal Format, below.
For storage requirements, see Data Type Storage
Requirements.
Oracle Mode
In Oracle mode from MariaDB 10.3, DATE with a time portion
is a synonym for DATETIME.
Internal Format
In MariaDB 10.1.2 a new temporal format was introduced from
MySQL 5.6 that alters how the TIME, DATETIME and TIMESTAMP
columns operate at lower levels. These changes allow these
temporal data types to have fractional parts and negative
values. You can disable this feature using the
mysql56_temporal_format system variable.
Tables that include TIMESTAMP values that were created on an
older version of MariaDB or that were created while the
mysql56_temporal_format system variable was disabled
continue to store data using the older data type format.
In order to update table columns from the older format to
the newer format, execute an ALTER TABLE... MODIFY COLUMN
statement that changes the column to the *same* data type.
This change may be needed if you want to export the table's
tablespace and import it onto a server that has
mysql56_temporal_format=ON set (see MDEV-15225).
For instance, if you have a DATETIME column in your table:
SHOW VARIABLES LIKE 'mysql56_temporal_format';
+-------------------------+-------+
| Variable_name | Value |
+-------------------------+-------+
| mysql56_temporal_format | ON |
+-------------------------+-------+
ALTER TABLE example_table MODIFY ts_col DATETIME;
When MariaDB executes the ALTER TABLE statement, it converts
the data from the older temporal format to the newer one.
In the event that you have several tables and columns using
temporal data types that you want to switch over to the new
format, make sure the system variable is enabled, then
perform a dump and restore using mysqldump. The columns
using relevant temporal data types are restored using the
new temporal format.
Examples
--------
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES ("2011-03-11"), ("2012-04-19
13:08:22"),
("2013-07-18 13:44:22.123456");
SELECT * FROM t1;
+---------------------+
| d |
+---------------------+
| 2011-03-11 00:00:00 |
| 2012-04-19 13:08:22 |
| 2013-07-18 13:44:22 |
+---------------------+
CREATE TABLE t2 (d DATETIME(6));
INSERT INTO t2 VALUES ("2011-03-11"), ("2012-04-19
13:08:22"),
("2013-07-18 13:44:22.123456");
SELECT * FROM t2;
+----------------------------+
| d |
+----------------------------+
| 2011-03-11 00:00:00.000000 |
| 2012-04-19 13:08:22.000000 |
| 2013-07-18 13:44:22.123456 |
+----------------------------++
Strings used in datetime context are automatically converted
to datetime(6). If you want to have a datetime without
seconds, you should use CONVERT(..,datetime).
SELECT CONVERT('2007-11-30 10:30:19',datetime);
+-----------------------------------------+
| CONVERT('2007-11-30 10:30:19',datetime) |
+-----------------------------------------+
| 2007-11-30 10:30:19 |
+-----------------------------------------+
SELECT CONVERT('2007-11-30 10:30:19',datetime(6));
+--------------------------------------------+
| CONVERT('2007-11-30 10:30:19',datetime(6)) |
+--------------------------------------------+
| 2007-11-30 10:30:19.000000 |
+--------------------------------------------+
URL: https://mariadb.com/kb/en/datetime/https://mariadb.com/kb/en/datetime/ ! _ * PolyFromWKBA synonym for ST_PolyFromWKB.
URL: https://mariadb.com/kb/en/wkb-polyfromwkb/https://mariadb.com/kb/en/wkb-polyfromwkb/ " ^ ) PolygonFromWKBA synonym for ST_PolyFromWKB.
URL: https://mariadb.com/kb/en/polygonfromwkb/https://mariadb.com/kb/en/polygonfromwkb/ # �& ST_AsBinarySyntax
------
ST_AsBinary(g)
AsBinary(g)
ST_AsWKB(g)
AsWKB(g)
Description
-----------
Converts a value in internal geometry format to its WKB
representation and returns the binary result.
ST_AsBinary(), AsBinary(), ST_AsWKB() and AsWKB() are
synonyms,
Examples
--------
SET @poly = ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0
0))');
SELECT ST_AsBinary(@poly);
SELECT ST_AsText(ST_GeomFromWKB(ST_AsWKB(@poly)));
+--------------------------------------------+
| ST_AsText(ST_GeomFromWKB(ST_AsWKB(@poly))) |
+--------------------------------------------+
| POLYGON((0 0,0 1,1 1,1 0,0 0)) |
+--------------------------------------------+
URL: https://mariadb.com/kb/en/st_asbinary/https://mariadb.com/kb/en/st_asbinary/ $ W # ST_AsWKBA synonym for ST_AsBinary().
URL: https://mariadb.com/kb/en/st_aswkb/https://mariadb.com/kb/en/st_aswkb/ & p 7 ST_GeometryCollectionFromWKBA synonym for ST_GeomCollFromWKB.
URL: https://mariadb.com/kb/en/st_geometrycollectionfromwkb/https://mariadb.com/kb/en/st_geometrycollectionfromwkb/ ' b - ST_GeometryFromWKBA synonym for ST_GeomFromWKB.
URL: https://mariadb.com/kb/en/st_geometryfromwkb/https://mariadb.com/kb/en/st_geometryfromwkb/ � � �� >� =�� �� � \�%B �� �" DECIMALSyntax
------
DECIMAL[(M[,D])] [SIGNED | UNSIGNED | ZEROFILL]
Description
-----------
A packed "exact" fixed-point number. M is the total number
of digits (the
precision) and D is the number of digits after the decimal
point (the
scale). The decimal point and (for negative numbers) the
"-" sign are not
counted in M. If D is 0, values have no decimal point or
fractional
part and on INSERT the value will be rounded to the nearest
DECIMAL. The maximum number of digits (M) for DECIMAL is 65.
The maximum number of supported decimals (D) is 30 before
MariadB 10.2.1 and 38 afterwards. If D is omitted, the
default is 0. If M is omitted, the default is 10.
UNSIGNED, if specified, disallows negative values.
ZEROFILL, if specified, pads the number with zeros, up to
the total number
of digits specified by M.
All basic calculations (+, -, *, /) with DECIMAL columns are
done with
a precision of 65 digits.
For more details on the attributes, see Numeric Data Type
Overview.
Oracle Mode
In Oracle mode from MariaDB 10.3, NUMBER is a synonym.
Examples
--------
CREATE TABLE t1 (d DECIMAL UNSIGNED ZEROFILL);
INSERT INTO t1 VALUES (1),(2),(3),(4.0),(5.2),(5.7);
Query OK, 6 rows affected, 2 warnings (0.16 sec)
Records: 6 Duplicates: 0 Warnings: 2
Note (Code 1265): Data truncated for column 'd' at row 5
Note (Code 1265): Data truncated for column 'd' at row 6
SELECT * FROM t1;
+------------+
| d |
+------------+
| 0000000001 |
| 0000000002 |
| 0000000003 |
| 0000000004 |
| 0000000005 |
| 0000000006 |
+------------+
INSERT INTO t1 VALUES (-7);
ERROR 1264 (22003): Out of range value for column 'd' at
row 1
URL: https://mariadb.com/kb/en/decimal/https://mariadb.com/kb/en/decimal/ � ENUMSyntax
------
ENUM('value1','value2',...) [CHARACTER SET charset_name]
[COLLATE collation_name]
Description
-----------
An enumeration. A string object that can have only one
value, chosen
from the list of values 'value1', 'value2', ..., NULL or
the special
'' error value. In theory, an ENUM column can have a
maximum of 65,535 distinct
values; in practice, the real maximum depends on many
factors. ENUM values are represented internally as integers.
Trailing spaces are automatically stripped from ENUM values
on table creation.
ENUMs require relatively little storage space compared to
strings, either one or two bytes depending on the number of
enumeration values.
NULL and empty values
An ENUM can also contain NULL and empty values. If the ENUM
column is declared to permit NULL values, NULL becomes a
valid value, as well as the default value (see below). If
strict SQL Mode is not enabled, and an invalid value is
inserted into an ENUM, a special empty string, with an index
value of zero (see Numeric index, below), is inserted, with
a warning. This may be confusing, because the empty string
is also a possible value, and the only difference if that in
this case its index is not 0. Inserting will fail with an
error if strict mode is active.
If a DEFAULT clause is missing, the default value will be:
NULL is the column is nullable;
otherwise, the first value in the enumaration.
Numeric index
ENUM values are indexed numerically in the order they are
defined, and sorting will be performed in this numeric
order. We suggest not using ENUM to store numerals, as there
is little to no storage space benefit, and it is easy to
confuse the enum integer with the enum numeral value by
leaving out the quotes.
An ENUM defined as ENUM('apple','orange','pear') would
have the following index values:
Index | Value |
NULL | NULL |
0 | '' |
1 | 'apple' |
2 | 'orange' |
3 | 'pear' |
Examples
--------
CREATE TABLE fruits (
id INT NOT NULL auto_increment PRIMARY KEY,
fruit ENUM('apple','orange','pear'),
bushels INT);
DESCRIBE fruits;
+---------+-------------------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------+-------------------------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| fruit | enum('apple','orange','pear') | YES | | NULL
| |
| bushels | int(11) | YES | | NULL | |
+---------+-------------------------------+------+-----+---------+----------------+
INSERT INTO fruits
(fruit,bushels) VALUES
('pear',20),
('apple',100),
('orange',25);
INSERT INTO fruits
(fruit,bushels) VALUES
('avocado',10);
ERROR 1265 (01000): Data truncated for column 'fruit' at
row 1
SELECT * FROM fruits;
+----+--------+---------+
| id | fruit | bushels |
+----+--------+---------+
| 1 | pear | 20 |
| 2 | apple | 100 |
| 3 | orange | 25 |
+----+--------+---------+
Selecting by numeric index:
SELECT * FROM fruits WHERE fruit=2;
+----+--------+---------+
| id | fruit | bushels |
+----+--------+---------+
| 3 | orange | 25 |
+----+--------+---------+
Sorting is according to the index value:
CREATE TABLE enums (a ENUM('2','1'));
INSERT INTO enums VALUES ('1'),('2');
SELECT * FROM enums ORDER BY a ASC;
+------+
| a |
+------+
| 2 |
| 1 |
+------+
It's easy to get confused between returning the enum
integer with the stored value, so we don't suggest using
ENUM to store numerals. The first example returns the 1st
indexed field ('2' has an index value of 1, as it's
defined first), while the second example returns the string
value '1'.
SELECT * FROM enums WHERE a=1;
+------+
| a |
+------+
| 2 |
+------+
SELECT * FROM enums WHERE a='1';
+------+
| a |
+------+
| 1 |
+------+
URL: https://mariadb.com/kb/en/enum/https://mariadb.com/kb/en/enum/ ( �) ST_GeomFromWKBSyntax
------
ST_GeomFromWKB(wkb[,srid])
ST_GeometryFromWKB(wkb[,srid])
GeomFromWKB(wkb[,srid])
GeometryFromWKB(wkb[,srid])
Description
-----------
Constructs a geometry value of any type using its WKB
representation and SRID.
ST_GeomFromWKB(), ST_GeometryFromWKB(), GeomFromWKB() and
GeometryFromWKB() are synonyms.
Examples
--------
SET @g = ST_AsBinary(ST_LineFromText('LINESTRING(0 4, 4
6)'));
SELECT ST_AsText(ST_GeomFromWKB(@g));
+-------------------------------+
| ST_AsText(ST_GeomFromWKB(@g)) |
+-------------------------------+
| LINESTRING(0 4,4 6) |
+-------------------------------+
URL: https://mariadb.com/kb/en/st_geomfromwkb/https://mariadb.com/kb/en/st_geomfromwkb/ ) j) ST_LineFromWKBSyntax
------
ST_LineFromWKB(wkb[,srid])
LineFromWKB(wkb[,srid])
ST_LineStringFromWKB(wkb[,srid])
LineStringFromWKB(wkb[,srid])
Description
-----------
Constructs a LINESTRING value using its WKB representation
and SRID.
ST_LineFromWKB(), LineFromWKB(), ST_LineStringFromWKB(), and
LineStringFromWKB() are synonyms.
Examples
--------
SET @g = ST_AsBinary(ST_LineFromText('LineString(0 4,4
6)'));
SELECT ST_AsText(ST_LineFromWKB(@g)) AS l;
+---------------------+
| l |
+---------------------+
| LINESTRING(0 4,4 6) |
+---------------------+
URL: https://mariadb.com/kb/en/st_linefromwkb/https://mariadb.com/kb/en/st_linefromwkb/ * d / ST_LineStringFromWKBA synonym for ST_LineFromWKB.
URL: https://mariadb.com/kb/en/st_linestringfromwkb/https://mariadb.com/kb/en/st_linestringfromwkb/ + �* ST_PointFromWKBSyntax
------
ST_PointFromWKB(wkb[,srid])
PointFromWKB(wkb[,srid])
Description
-----------
Constructs a POINT value using its WKB representation and
SRID.
ST_PointFromWKB() and PointFromWKB() are synonyms.
Examples
--------
SET @g = ST_AsBinary(ST_PointFromText('POINT(0 4)'));
SELECT ST_AsText(ST_PointFromWKB(@g)) AS p;
+------------+
| p |
+------------+
| POINT(0 4) |
+------------+
URL: https://mariadb.com/kb/en/st_pointfromwkb/https://mariadb.com/kb/en/st_pointfromwkb/ < �� �����! �87&�
�� ! DOUBLESyntax
------
DOUBLE[(M,D)] [SIGNED | UNSIGNED | ZEROFILL]
DOUBLE PRECISION[(M,D)] [SIGNED | UNSIGNED | ZEROFILL]
REAL[(M,D)] [SIGNED | UNSIGNED | ZEROFILL]
Description
-----------
A normal-size (double-precision) floating-point number (see
FLOAT for a single-precision floating-point number).
Allowable values are:
-1.7976931348623157E+308 to -2.2250738585072014E-308
0
2.2250738585072014E-308 to 1.7976931348623157E+308
These are the theoretical limits, based on the IEEE
standard. The actual range
might be slightly smaller depending on your hardware or
operating system.
M is the total number of digits and D is the number of
digits
following the decimal point. If M and D are omitted, values
are stored
to the limits allowed by the hardware. A double-precision
floating-point number is accurate to approximately 15
decimal places.
UNSIGNED, if specified, disallows negative values.
ZEROFILL, if specified, pads the number with zeros, up to
the total number
of digits specified by M.
REAL and DOUBLE PRECISION are synonyms, unless the
REAL_AS_FLOAT SQL mode is enabled, in which case REAL is a
synonym for FLOAT rather than DOUBLE.
See Floating Point Accuracy for issues when using
floating-point numbers.
For more details on the attributes, see Numeric Data Type
Overview.
Examples
--------
CREATE TABLE t1 (d DOUBLE(5,0) zerofill);
INSERT INTO t1 VALUES (1),(2),(3),(4);
SELECT * FROM t1;
+-------+
| d |
+-------+
| 00001 |
| 00002 |
| 00003 |
| 00004 |
+-------+
URL: https://mariadb.com/kb/en/double/https://mariadb.com/kb/en/double/ FLOATSyntax
------
FLOAT[(M,D)] [SIGNED | UNSIGNED | ZEROFILL]
Description
-----------
A small (single-precision) floating-point number (see DOUBLE
for a regular-size floating point number). Allowable values
are:
-3.402823466E+38 to -1.175494351E-38
0
1.175494351E-38 to 3.402823466E+38.
These are the theoretical limits, based on the IEEE
standard. The actual range might be slightly smaller
depending on your
hardware or operating system.
M is the total number of digits and D is the number of
digits
following the decimal point. If M and D are omitted, values
are stored
to the limits allowed by the hardware. A single-precision
floating-point number is accurate to approximately 7 decimal
places.
UNSIGNED, if specified, disallows negative values.
Using FLOAT might give you some unexpected problems because
all
calculations in MariaDB are done with double precision. See
Floating Point Accuracy.
For more details on the attributes, see Numeric Data Type
Overview.
URL: https://mariadb.com/kb/en/float/https://mariadb.com/kb/en/float/ ) JSON Data TypeThe JSON alias was added in MariaDB 10.2.7. This was done to
make it possible to use JSON columns in statement based
replication from MySQL to MariaDB and to make it possible
for MariaDB to read mysqldumps from MySQL.
JSON is an alias for LONGTEXT introduced for compatibility
reasons with MySQL's JSON data type. MariaDB implements
this as a LONGTEXT rather, as the JSON data type contradicts
the SQL standard, and MariaDB's benchmarks indicate that
performance is at least equivalent.
In order to ensure that a a valid json document is inserted,
the JSON_VALID function can be used as a CHECK constraint.
This constraint is automatically included for types using
the JSON alias from MariaDB 10.4.3.
Examples
--------
CREATE TABLE t (j JSON);
DESC t;
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| j | longtext | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
With validation:
CREATE TABLE t2 (
j JSON
CHECK (JSON_VALID(j))
);
INSERT INTO t2 VALUES ('invalid');
ERROR 4025 (23000): CONSTRAINT `j` failed for `test`.`t2`
INSERT INTO t2 VALUES ('{"id": 1, "name":
"Monty"}');
Query OK, 1 row affected (0.13 sec)
Replicating JSON Data Between MySQL and MariaDB
The JSON type in MySQL stores the JSON object in a compact
form, not as LONGTEXT as in MariaDB.
This means that row based replication will not work for JSON
types from MySQL to MariaDB.
There are a a few different ways to solve this:
Use statement based replication.
Change the JSON column to type TEXT in MySQL
Converting a MySQL TABLE with JSON Fields to MariaDB
MariaDB can't directly access MySQL's JSON format.
There are a a few different ways to move the table to
MariaDB:
Change the JSON column to type TEXT in MySQL. After this,
MariaDB can directly use the table without any need for a
dump and restore.
Use mysqldump to copy the table.
Differences Between MySQL JSON Strings and MariaDB JSON
Strings
In MySQL, JSON is an object and is compared according to
json values. In MariaDB JSON strings are normal strings and
compared as strings. One exception is when using
JSON_EXTRACT() in which case strings are unescaped before
comparison.
URL: https://mariadb.com/kb/en/json-data-type/https://mariadb.com/kb/en/json-data-type/ , �) ST_PolyFromWKBSyntax
------
ST_PolyFromWKB(wkb[,srid])
ST_PolygonFromWKB(wkb[,srid])
PolyFromWKB(wkb[,srid])
PolygonFromWKB(wkb[,srid])
Description
-----------
Constructs a POLYGON value using its WKB representation and
SRID.
ST_PolyFromWKB(), ST_PolygonFromWKB(), PolyFromWKB() and
PolygonFromWKB() are synonyms.
Examples
--------
SET @g = ST_AsBinary(ST_PolyFromText('POLYGON((1 1,1 5,4
9,6 9,9 3,7 2,1 1))'));
SELECT ST_AsText(ST_PolyFromWKB(@g)) AS p;
+----------------------------------------+
| p |
+----------------------------------------+
| POLYGON((1 1,1 5,4 9,6 9,9 3,7 2,1 1)) |
+----------------------------------------+
URL: https://mariadb.com/kb/en/st_polyfromwkb/https://mariadb.com/kb/en/st_polyfromwkb/ - a , ST_PolygonFromWKBA synonym for ST_PolyFromWKB.
URL: https://mariadb.com/kb/en/st_polygonfromwkb/https://mariadb.com/kb/en/st_polygonfromwkb/ . i 7 $ BOUNDARYA synonym for ST_BOUNDARY.
URL: https://mariadb.com/kb/en/geometry-properties-boundary/https://mariadb.com/kb/en/geometry-properties-boundary/ / W $ $ DIMENSIONA synonym for ST_DIMENSION.
URL: https://mariadb.com/kb/en/dimension/https://mariadb.com/kb/en/dimension/ 0 i 7 $ ENVELOPEA synonym for ST_ENVELOPE.
URL: https://mariadb.com/kb/en/geometry-properties-envelope/https://mariadb.com/kb/en/geometry-properties-envelope/ 1 k 8 $ GeometryNA synonym for ST_GeometryN.
URL:
https://mariadb.com/kb/en/geometry-properties-geometryn/https://mariadb.com/kb/en/geometry-properties-geometryn/ 2 q ; $ GeometryTypeA synonym for ST_GeometryType.
URL:
https://mariadb.com/kb/en/geometry-properties-geometrytype/https://mariadb.com/kb/en/geometry-properties-geometrytype/ 3 U # $ IsClosedA synonym for ST_IsClosed.
URL: https://mariadb.com/kb/en/isclosed/https://mariadb.com/kb/en/isclosed/ 4 g 6 $ IsEmptyA synonym for ST_IsEmpty.
URL: https://mariadb.com/kb/en/geometry-properties-isempty/https://mariadb.com/kb/en/geometry-properties-isempty/ 5 Q ! $ IsRingA synonym for ST_IsRing.
URL: https://mariadb.com/kb/en/isring/https://mariadb.com/kb/en/isring/ P � �� � J� �� �� H� �� �� ���
U U> I�/�� �� &) Geometry TypesDescription
-----------
MariaDB provides a standard way of creating spatial columns
for geometry types,
for example, with CREATE TABLE or ALTER TABLE.
Currently, spatial columns are supported for MyISAM, InnoDB,
NDB, and ARCHIVE
tables. See also SPATIAL INDEX.
The basic geometry type is GEOMETRY. But the type can be
more specific. The following types are supported:
Geometry Types |
POINT |
LINESTRING |
POLYGON |
MULTIPOINT |
MULTILINESTRING |
MULTIPOLYGON |
GEOMETRYCOLLECTION |
GEOMETRY |
Examples
--------
Note: For clarity, only one type is listed per table in the
examples below, but a table
row can contain multiple types. For example:
CREATE TABLE object (shapeA POLYGON, shapeB LINESTRING);
POINT
CREATE TABLE gis_point (g POINT);
SHOW FIELDS FROM gis_point;
INSERT INTO gis_point VALUES
(PointFromText('POINT(10 10)')),
(PointFromText('POINT(20 10)')),
(PointFromText('POINT(20 20)')),
(PointFromWKB(AsWKB(PointFromText('POINT(10 20)'))));
LINESTRING
CREATE TABLE gis_line (g LINESTRING);
SHOW FIELDS FROM gis_line;
INSERT INTO gis_line VALUES
(LineFromText('LINESTRING(0 0,0 10,10 0)')),
(LineStringFromText('LINESTRING(10 10,20 10,20 20,10 20,10
10)')),
(LineStringFromWKB(AsWKB(LineString(Point(10, 10),
Point(40, 10)))));
POLYGON
CREATE TABLE gis_polygon (g POLYGON);
SHOW FIELDS FROM gis_polygon;
INSERT INTO gis_polygon VALUES
(PolygonFromText('POLYGON((10 10,20 10,20 20,10 20,10
10))')),
(PolyFromText('POLYGON((0 0,50 0,50 50,0 50,0 0), (10
10,20 10,20 20,10 20,10 10))')),
(PolyFromWKB(AsWKB(Polygon(LineString(Point(0, 0),
Point(30, 0), Point(30, 30), Point(0, 0))))));
MULTIPOINT
CREATE TABLE gis_multi_point (g MULTIPOINT);
SHOW FIELDS FROM gis_multi_point;
INSERT INTO gis_multi_point VALUES
(MultiPointFromText('MULTIPOINT(0 0,10 10,10 20,20
20)')),
(MPointFromText('MULTIPOINT(1 1,11 11,11 21,21 21)')),
(MPointFromWKB(AsWKB(MultiPoint(Point(3, 6), Point(4,
10)))));
MULTILINESTRING
CREATE TABLE gis_multi_line (g MULTILINESTRING);
SHOW FIELDS FROM gis_multi_line;
INSERT INTO gis_multi_line VALUES
(MultiLineStringFromText('MULTILINESTRING((10 48,10 21,10
0),(16 0,16 23,16 48))')),
(MLineFromText('MULTILINESTRING((10 48,10 21,10 0))')),
(MLineFromWKB(AsWKB(MultiLineString(LineString(Point(1, 2),
Point(3, 5)), LineString(Point(2, 5), Point(5, 8), Point(21,
7))))));
MULTIPOLYGON
CREATE TABLE gis_multi_polygon (g MULTIPOLYGON);
SHOW FIELDS FROM gis_multi_polygon;
INSERT INTO gis_multi_polygon VALUES
(MultiPolygonFromText('MULTIPOLYGON(((28 26,28 0,84 0,84
42,28 26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67
13,59 13,59 18)))')),
(MPolyFromText('MULTIPOLYGON(((28 26,28 0,84 0,84 42,28
26),(52 18,66 23,73 9,48 6,52 18)),((59 18,67 18,67 13,59
13,59 18)))')),
(MPolyFromWKB(AsWKB(MultiPolygon(Polygon(LineString(Point(0,
3), Point(3, 3), Point(3, 0), Point(0, 3)))))));
GEOMETRYCOLLECTION
CREATE TABLE gis_geometrycollection (g GEOMETRYCOLLECTION);
SHOW FIELDS FROM gis_geometrycollection;
INSERT INTO gis_geometrycollection VALUES
(GeomCollFromText('GEOMETRYCOLLECTION(POINT(0 0),
LINESTRING(0 0,10 10))')),
(GeometryFromWKB(AsWKB(GeometryCollection(Point(44, 6),
LineString(Point(3, 6), Point(7, 9)))))),
(GeomFromText('GeometryCollection()')),
(GeomFromText('GeometryCollection EMPTY'));
GEOMETRY
CREATE TABLE gis_geometry (g GEOMETRY);
SHOW FIELDS FROM gis_geometry;
INSERT into gis_geometry SELECT * FROM gis_point;
INSERT into gis_geometry SELECT * FROM gis_line;
INSERT into gis_geometry SELECT * FROM gis_polygon;
INSERT into gis_geometry SELECT * FROM gis_multi_point;
INSERT into gis_geometry SELECT * FROM gis_multi_line;
INSERT into gis_geometry SELECT * FROM gis_multi_polygon;
INSERT into gis_geometry SELECT * FROM
gis_geometrycollection;
URL: https://mariadb.com/kb/en/geometry-types/https://mariadb.com/kb/en/geometry-types/ a$ MEDIUMINTSyntax
------
MEDIUMINT[(M)] [SIGNED | UNSIGNED | ZEROFILL]
Description
-----------
A medium-sized integer. The signed range is -8388608 to
8388607. The
unsigned range is 0 to 16777215.
ZEROFILL pads the integer with zeroes and assumes UNSIGNED
(even if UNSIGNED is not specified).
For details on the attributes, see Numeric Data Type
Overview.
Examples
--------
CREATE TABLE mediumints (a MEDIUMINT,b MEDIUMINT UNSIGNED,c
MEDIUMINT ZEROFILL);
DESCRIBE mediumints;
+-------+--------------------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------------------------+------+-----+---------+-------+
| a | mediumint(9) | YES | | NULL | |
| b | mediumint(8) unsigned | YES | | NULL | |
| c | mediumint(8) unsigned zerofill | YES | | NULL | |
+-------+--------------------------------+------+-----+---------+-------+
INSERT INTO mediumints VALUES (-10,-10,-10);
Query OK, 1 row affected, 2 warnings (0.05 sec)
Warning (Code 1264): Out of range value for column 'b' at
row 1
Warning (Code 1264): Out of range value for column 'c' at
row 1
INSERT INTO mediumints VALUES (-10,10,-10);
Query OK, 1 row affected, 1 warning (0.08 sec)
Warning (Code 1264): Out of range value for column 'c' at
row 1
INSERT INTO mediumints VALUES (-10,10,10);
INSERT INTO mediumints VALUES (8388608,8388608,8388608);
Query OK, 1 row affected, 1 warning (0.05 sec)
Warning (Code 1264): Out of range value for column 'a' at
row 1
INSERT INTO mediumints VALUES (8388607,8388608,8388608);
SELECT * FROM mediumints;
+---------+---------+----------+
| a | b | c |
+---------+---------+----------+
| -10 | 0 | 00000000 |
| -10 | 0 | 00000000 |
| -10 | 10 | 00000000 |
| -10 | 10 | 00000010 |
| 8388607 | 8388608 | 08388608 |
| 8388607 | 8388608 | 08388608 |
+---------+---------+----------+
URL: https://mariadb.com/kb/en/mediumint/https://mariadb.com/kb/en/mediumint/ 6 i 7 $ IsSimpleA synonym for ST_IsSImple.
URL: https://mariadb.com/kb/en/geometry-properties-issimple/https://mariadb.com/kb/en/geometry-properties-issimple/ 7
s < $ NumGeometriesA synonym for ST_NumGeometries.
URL:
https://mariadb.com/kb/en/geometry-properties-numgeometries/https://mariadb.com/kb/en/geometry-properties-numgeometries/ 8 a 3 $ SRIDA synonym for ST_SRID.
URL: https://mariadb.com/kb/en/geometry-properties-srid/https://mariadb.com/kb/en/geometry-properties-srid/ : �' $ ST_DIMENSIONSyntax
------
ST_Dimension(g)
Dimension(g)
Description
-----------
Returns the inherent dimension of the geometry value g. The
result can
be
Dimension | Definition |
-1 | empty geometry |
0 | geometry with no length or area |
1 | geometry with no area but nonzero length |
2 | geometry with nonzero area |
ST_Dimension() and Dimension() are synonyms.
Examples
--------
SELECT Dimension(GeomFromText('LineString(1 1,2 2)'));
+------------------------------------------------+
| Dimension(GeomFromText('LineString(1 1,2 2)')) |
+------------------------------------------------+
| 1 |
+------------------------------------------------+
URL: https://mariadb.com/kb/en/st_dimension/https://mariadb.com/kb/en/st_dimension/ < X' $ ST_GEOMETRYNSyntax
------
ST_GeometryN(gc,N)
GeometryN(gc,N)
Description
-----------
Returns the N-th geometry in the GeometryCollection gc.
Geometries are numbered beginning with 1.
ST_GeometryN() and GeometryN() are synonyms.
Example
SET @gc = 'GeometryCollection(Point(1 1),LineString(12 14,
9 11))';
SELECT AsText(GeometryN(GeomFromText(@gc),1));
+----------------------------------------+
| AsText(GeometryN(GeomFromText(@gc),1)) |
+----------------------------------------+
| POINT(1 1) |
+----------------------------------------+
URL: https://mariadb.com/kb/en/st_geometryn/https://mariadb.com/kb/en/st_geometryn/ N �9�� �� � w� k/2q � �5 Numeric Data Type OverviewThere are a number of numeric data types:
TINYINT
BOOLEAN - Synonym for TINYINT(1)
SMALLINT
MEDIUMINT
INT, INTEGER
BIGINT
DECIMAL, DEC, NUMERIC, FIXED
FLOAT
DOUBLE, DOUBLE PRECISION, REAL
BIT
See the specific articles for detailed information on each.
SIGNED, UNSIGNED and ZEROFILL
Most numeric types can be defined as SIGNED, UNSIGNED or
ZEROFILL, for example:
TINYINT[(M)] [SIGNED | UNSIGNED | ZEROFILL]
If SIGNED, or no attribute, is specified, a portion of the
numeric type will be reserved for the sign (plus or minus).
For example, a TINYINT SIGNED can range from -128 to 127.
If UNSIGNED is specified, no portion of the numeric type is
reserved for the sign, so for integer types range can be
larger. For example, a TINYINT UNSIGNED can range from 0 to
255. Floating point and fixed-point types also can be
UNSIGNED, but this only prevents negative values from being
stored and doesn't alter the range.
If ZEROFILL is specified, the column will be set to UNSIGNED
and the spaces used by default to pad the field are replaced
with zeros. ZEROFILL is ignored in expressions or as part of
a UNION. ZEROFILL is a non-standard MySQL and MariaDB
enhancement.
Note that although the preferred syntax indicates that the
attributes are exclusive, more than one attribute can be
specified.
Until MariaDB 10.2.7 (MDEV-8659), any combination of the
attributes could be used in any order, with duplicates. In
this case:
the presence of ZEROFILL makes the column UNSIGNED ZEROFILL.
the presence of UNSIGNED makes the column UNSIGNED.
From MariaDB 10.2.8, only the following combinations are
supported:
SIGNED
UNSIGNED
ZEROFILL
UNSIGNED ZEROFILL
ZEROFILL UNSIGNED
The latter two should be replaced with simply ZEROFILL, but
are still accepted by the parser.
Examples
--------
CREATE TABLE zf (
i1 TINYINT SIGNED,
i2 TINYINT UNSIGNED,
i3 TINYINT ZEROFILL
);
INSERT INTO zf VALUES (2,2,2);
SELECT * FROM zf;
+------+------+------+
| i1 | i2 | i3 |
+------+------+------+
| 2 | 2 | 002 |
+------+------+------+
Range
When attempting to add a value that is out of the valid
range for the numeric type, MariaDB will react depending on
the strict SQL_MODE setting.
If strict_mode has been set (the default from MariaDB
10.2.4), MariaDB will return an error.
If strict_mode has not been set (the default until MariaDB
10.2.3), MariaDB will adjust the number to fit in the field,
returning a warning.
Examples
--------
With strict_mode set:
SHOW VARIABLES LIKE 'sql_mode';
+---------------+-------------------------------------------------------------------------------------------+
| Variable_name | Value |
+---------------+-------------------------------------------------------------------------------------------+
| sql_mode |
STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
|
+---------------+-------------------------------------------------------------------------------------------+
CREATE TABLE ranges (i1 TINYINT, i2 SMALLINT, i3 TINYINT
UNSIGNED);
INSERT INTO ranges VALUES (257,257,257);
ERROR 1264 (22003): Out of range value for column 'i1' at
row 1
SELECT * FROM ranges;
Empty set (0.10 sec)
With strict_mode unset:
SHOW VARIABLES LIKE 'sql_mode%';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| sql_mode | |
+---------------+-------+
CREATE TABLE ranges (i1 TINYINT, i2 SMALLINT, i3 TINYINT
UNSIGNED);
INSERT INTO ranges VALUES (257,257,257);
Query OK, 1 row affected, 2 warnings (0.00 sec)
SHOW WARNINGS;
+---------+------+---------------------------------------------+
| Level | Code | Message |
+---------+------+---------------------------------------------+
| Warning | 1264 | Out of range value for column 'i1' at
row 1 |
| Warning | 1264 | Out of range value for column 'i3' at
row 1 |
+---------+------+---------------------------------------------+
2 rows in set (0.00 sec)
SELECT * FROM ranges;
+------+------+------+
| i1 | i2 | i3 |
+------+------+------+
| 127 | 257 | 255 |
+------+------+------+
Auto_increment
The AUTO_INCREMENT attribute can be used to generate a
unique identity for new rows. For more details, see
auto_increment.
URL: https://mariadb.com/kb/en/numeric-data-type-overview/https://mariadb.com/kb/en/numeric-data-type-overview/ ! �# SMALLINTSyntax
------
SMALLINT[(M)] [SIGNED | UNSIGNED | ZEROFILL]
Description
-----------
A small integer. The signed range is -32768 to 32767. The
unsigned range is 0 to 65535.
If a column has been set to ZEROFILL, all values will be
prepended by zeros so that the SMALLINT value contains a
number of M digits.
Note: If the ZEROFILL attribute has been specified, the
column will automatically become UNSIGNED.
For more details on the attributes, see Numeric Data Type
Overview.
Examples
--------
CREATE TABLE smallints (a SMALLINT,b SMALLINT UNSIGNED,c
SMALLINT ZEROFILL);
INSERT INTO smallints VALUES (-10,-10,-10);
Query OK, 1 row affected, 2 warnings (0.09 sec)
Warning (Code 1264): Out of range value for column 'b' at
row 1
Warning (Code 1264): Out of range value for column 'c' at
row 1
INSERT INTO smallints VALUES (-10,10,-10);
Query OK, 1 row affected, 1 warning (0.08 sec)
Warning (Code 1264): Out of range value for column 'c' at
row 1
INSERT INTO smallints VALUES (-10,10,10);
INSERT INTO smallints VALUES (32768,32768,32768);
Query OK, 1 row affected, 1 warning (0.04 sec)
Warning (Code 1264): Out of range value for column 'a' at
row 1
INSERT INTO smallints VALUES (32767,32768,32768);
SELECT * FROM smallints;
+-------+-------+-------+
| a | b | c |
+-------+-------+-------+
| -10 | 0 | 00000 |
| -10 | 10 | 00000 |
| -10 | 10 | 00010 |
| 32767 | 32768 | 32768 |
| 32767 | 32768 | 32768 |
+-------+-------+-------+
URL: https://mariadb.com/kb/en/smallint/https://mariadb.com/kb/en/smallint/ = l* $ ST_GEOMETRYTYPESyntax
------
ST_GeometryType(g)
GeometryType(g)
Description
-----------
Returns as a string the name of the geometry type of which
the
geometry instance g is a member. The name corresponds to one
of the
instantiable Geometry subclasses.
ST_GeometryType() and GeometryType() are synonyms.
Examples
--------
SELECT GeometryType(GeomFromText('POINT(1 1)'));
+------------------------------------------+
| GeometryType(GeomFromText('POINT(1 1)')) |
+------------------------------------------+
| POINT |
+------------------------------------------+
URL: https://mariadb.com/kb/en/st_geometrytype/https://mariadb.com/kb/en/st_geometrytype/ ?
�% $ ST_ISEMPTYSyntax
------
ST_IsEmpty(g)
IsEmpty(g)
Description
-----------
IsEmpty is a function defined by the OpenGIS specification,
but is not fully implemented by MariaDB or MySQL.
Since MariaDB and MySQL do not support GIS EMPTY values such
as POINT EMPTY, as implemented it simply returns 1 if the
geometry value g is invalid, 0 if it is valid, and NULL if
the argument is NULL.
ST_IsEmpty() and IsEmpty() are synonyms.
URL: https://mariadb.com/kb/en/st_isempty/https://mariadb.com/kb/en/st_isempty/ @ �$ $ ST_IsRingThe ST_IsRing function was introduced in MariaDB 10.1.2
Syntax
------
ST_IsRing(g)
IsRing(g)
Description
-----------
Returns true if a given LINESTRING is a ring, that is, both
ST_IsClosed and ST_IsSimple. A simple curve does not pass
through the same point more than once. However, see
MDEV-7510.
St_IsRing() and IsRing() are synonyms.
URL: https://mariadb.com/kb/en/st_isring/https://mariadb.com/kb/en/st_isring/ �� 2�# �X�� �� " �
* String LiteralsStrings are sequences of characters and are enclosed with
quotes.
The syntax is:
[_charset_name]'string' [COLLATE collation_name]
For example:
'The MariaDB Foundation'
_utf8 'Foundation' COLLATE utf8_unicode_ci;
Strings can either be enclosed in single quotes or in double
quotes (the same character must be used to both open and
close the string).
The ANSI SQL-standard does not permit double quotes for
enclosing strings, and although MariaDB does by default, if
the MariaDB server has enabled the ANSI_QUOTES_SQL SQL_MODE,
double quotes will be treated as being used for identifiers
instead of strings.
Strings that are next to each other are automatically
concatenated. For example:
'The ' 'MariaDB ' 'Foundation'
and
'The MariaDB Foundation'
are equivalent.
The \ (backslash character) is used to escape characters.
For example:
'MariaDB's new features'
is not a valid string because of the single quote in the
middle of the string, which is treated as if it closes the
string, but is actually meant as part of the string, an
apostrophe. The backslash character helps in situations like
this:
'MariaDB\'s new features'
is now a valid string, and if displayed, will appear without
the backslash.
SELECT 'MariaDB\'s new features';
+------------------------+
| MariaDB's new features |
+------------------------+
| MariaDB's new features |
+------------------------+
Another way to escape the quoting character is repeating it
twice:
SELECT 'I''m here', """Double""";
+----------+----------+
| I'm here | "Double" |
+----------+----------+
| I'm here | "Double" |
+----------+----------+
Escape sequences
There are other escape sequences also. Here is a full list:
Escape sequence | Character |
\0 | ASCII NUL (0x00). |
\' | Single quote (“'”). |
\" | Double quote (“"”). |
\b | Backspace. |
\n | Newline, or linefeed,. |
\r | Carriage return. |
\t | Tab. |
\Z | ASCII 26 (Control+Z). See note following the table. |
\\ | Backslash (“\”). |
\% | “%” character. See note following the table. |
\_ | A “_” character. See note following the table. |
Escaping the % and _ characters can be necessary when using
the LIKE operator, which treats them as special characters.
The ASCII 26 character (\Z) needs to be escaped when
included in a batch file which needs to be executed in
Windows. The reason is that ASCII 26, in Windows, is the end
of file (EOF).
Backslash (\), if not used as an escape character, must
always be escaped. When followed by a character that is not
in the above table, backslashes will simply be ignored.
URL: https://mariadb.com/kb/en/string-literals/https://mariadb.com/kb/en/string-literals/ # �
TEXTSyntax
------
TEXT[(M)] [CHARACTER SET charset_name] [COLLATE
collation_name]
Description
-----------
A TEXT column with a maximum length of 65,535 (216 - 1)
characters. The effective maximum length is less if the
value contains
multi-byte characters. Each TEXT value is stored using a
two-byte length
prefix that indicates the number of bytes in the value. If
you need a bigger storage, consider using MEDIUMTEXT
instead.
An optional length M can be given for this type. If this is
done, MariaDB
creates the column as the smallest TEXT type large enough to
hold values
M characters long.
Before MariaDB 10.2, all MariaDB collations were of type
PADSPACE, meaning that TEXT (as well as VARCHAR and CHAR
values) are compared without regard for trailing spaces.
This does not apply to the LIKE pattern-matching operator,
which takes into account trailing spaces.
Before MariaDB 10.2.1, BLOB and TEXT columns could not be
assigned a DEFAULT value. This restriction was lifted in
MariaDB 10.2.1.
Examples
--------
Trailing spaces:
CREATE TABLE strtest (d TEXT(10));
INSERT INTO strtest VALUES('Maria ');
SELECT d='Maria',d='Maria ' FROM strtest;
+-----------+--------------+
| d='Maria' | d='Maria ' |
+-----------+--------------+
| 1 | 1 |
+-----------+--------------+
SELECT d LIKE 'Maria',d LIKE 'Maria ' FROM strtest;
+----------------+-------------------+
| d LIKE 'Maria' | d LIKE 'Maria ' |
+----------------+-------------------+
| 0 | 1 |
+----------------+-------------------+
Difference between VARCHAR and TEXT
VARCHAR columns can be fully indexed. TEXT columns can only
be indexed over a specified length.
Using TEXT or BLOB in a SELECT query that uses temporary
tables for storing intermediate results will force the
temporary table to be disk based (using the Aria storage
engine instead of the memory storage engine, which is a bit
slower. This is not that bad as the Aria storage engine
caches the rows in memory. To get the benefit of this, one
should ensure that the aria_pagecache_buffer_size variable
is big enough to hold most of the row and index data for
temporary tables.
For Storage Engine Developers
Internally the full length of the VARCHAR column is
allocated inside each TABLE objects record[] structure. As
there are three such buffers, each open table will allocate
3 times max-length-to-store-varchar bytes of memory.
TEXT and BLOB columns are stored with a pointer (4 or 8
bytes) + a 1-4 bytes length. The TEXT data is only stored
once. This means that internally TEXT uses less memory for
each open table but instead has the additional overhead that
each TEXT object needs to be allocated and freed for each
row access (with some caching in between).
URL: https://mariadb.com/kb/en/text/https://mariadb.com/kb/en/text/ A $& $ ST_IsSimpleSyntax
------
ST_IsSimple(g)
IsSimple(g)
Description
-----------
Returns true if the given Geometry has no anomalous
geometric points, false if it does, or NULL if given a NULL
value.
ST_IsSimple() and IsSimple() are synonyms.
Examples
--------
A POINT is always simple.
SET @g = 'Point(1 2)';
SELECT ST_ISSIMPLE(GEOMFROMTEXT(@g));
+-------------------------------+
| ST_ISSIMPLE(GEOMFROMTEXT(@g)) |
+-------------------------------+
| 1 |
+-------------------------------+
URL: https://mariadb.com/kb/en/st_issimple/https://mariadb.com/kb/en/st_issimple/ B + $ ST_NUMGEOMETRIESSyntax
------
ST_NumGeometries(gc)
NumGeometries(gc)
Description
-----------
Returns the number of geometries in the GeometryCollection
gc.
ST_NumGeometries() and NumGeometries() are synonyms.
Example
SET @gc = 'GeometryCollection(Point(1 1),LineString(2 2, 3
3))';
SELECT NUMGEOMETRIES(GeomFromText(@gc));
+----------------------------------+
| NUMGEOMETRIES(GeomFromText(@gc)) |
+----------------------------------+
| 2 |
+----------------------------------+
URL: https://mariadb.com/kb/en/st_numgeometries/https://mariadb.com/kb/en/st_numgeometries/ C �$ $ ST_RELATEThe ST_RELATE() function was introduced in MariaDB 10.1.2
Syntax
------
ST_Relate(g1, g2, i)
Description
-----------
Returns true if Geometry g1 is spatially related to
Geometryg2 by testing for intersections between the
interior, boundary and exterior of the two geometries as
specified by the values in intersection matrix pattern i.
URL: https://mariadb.com/kb/en/st_relate/https://mariadb.com/kb/en/st_relate/ D �" $ ST_SRIDSyntax
------
ST_SRID(g)
SRID(g)
Description
-----------
Returns an integer indicating the Spatial Reference System
ID for the
geometry value g.
In MariaDB, the SRID value is just an integer associated
with the
geometry value. All calculations are done assuming Euclidean
(planar)
geometry.
ST_SRID() and SRID() are synonyms.
Examples
--------
SELECT SRID(GeomFromText('LineString(1 1,2 2)',101));
+-----------------------------------------------+
| SRID(GeomFromText('LineString(1 1,2 2)',101)) |
+-----------------------------------------------+
| 101 |
+-----------------------------------------------+
URL: https://mariadb.com/kb/en/st_srid/https://mariadb.com/kb/en/st_srid/ Y ���)d�c�
�
�
�0 �> $ �
TIMESyntax
------
TIME [()]
Description
-----------
A time. The range is '-838:59:59.999999' to
'838:59:59.999999'. Microsecond precision can be from 0-6;
if not specified 0 is used. Microseconds have been available
since MariaDB 5.3.
MariaDB displays TIME values in 'HH:MM:SS.ssssss' format,
but allows assignment of times in looser formats, including
'D HH:MM:SS', 'HH:MM:SS', 'HH:MM', 'D HH:MM', 'D
HH', 'SS', or 'HHMMSS', as well as permitting dropping
of any leading zeros when a delimiter is provided, for
example '3:9:10'. For details, see date and time literals.
MariaDB 10.1.2 introduced the --mysql56-temporal-format
option, on by default, which allows MariaDB to store TIMEs
using the same low-level format MySQL 5.6 uses.
Internal Format
In MariaDB 10.1.2 a new temporal format was introduced from
MySQL 5.6 that alters how the TIME, DATETIME and TIMESTAMP
columns operate at lower levels. These changes allow these
temporal data types to have fractional parts and negative
values. You can disable this feature using the
mysql56_temporal_format system variable.
Tables that include TIMESTAMP values that were created on an
older version of MariaDB or that were created while the
mysql56_temporal_format system variable was disabled
continue to store data using the older data type format.
In order to update table columns from the older format to
the newer format, execute an ALTER TABLE... MODIFY COLUMN
statement that changes the column to the *same* data type.
This change may be needed if you want to export the table's
tablespace and import it onto a server that has
mysql56_temporal_format=ON set (see MDEV-15225).
For instance, if you have a TIME column in your table:
SHOW VARIABLES LIKE 'mysql56_temporal_format';
+-------------------------+-------+
| Variable_name | Value |
+-------------------------+-------+
| mysql56_temporal_format | ON |
+-------------------------+-------+
ALTER TABLE example_table MODIFY ts_col TIME;
When MariaDB executes the ALTER TABLE statement, it converts
the data from the older temporal format to the newer one.
In the event that you have several tables and columns using
temporal data types that you want to switch over to the new
format, make sure the system variable is enabled, then
perform a dump and restore using mysqldump. The columns
using relevant temporal data types are restored using the
new temporal format.
Examples
--------
INSERT INTO time VALUES ('90:00:00'), ('800:00:00'),
(800), (22), (151413), ('9:6:3'), ('12 09');
SELECT * FROM time;
+-----------+
| t |
+-----------+
| 90:00:00 |
| 800:00:00 |
| 00:08:00 |
| 00:00:22 |
| 15:14:13 |
| 09:06:03 |
| 297:00:00 |
+-----------+
URL: https://mariadb.com/kb/en/time/https://mariadb.com/kb/en/time/ ' x" TINYINTSyntax
------
TINYINT[(M)] [SIGNED | UNSIGNED | ZEROFILL]
Description
-----------
A very small integer. The signed range is -128 to 127. The
unsigned range is 0 to 255. For details on the attributes,
see Numeric Data Type Overview.
Examples
--------
CREATE TABLE tinyints (a TINYINT,b TINYINT UNSIGNED,c
TINYINT ZEROFILL);
Query OK, 0 rows affected (0.43 sec)
INSERT INTO tinyints VALUES (-10,-10,-10);
Query OK, 1 row affected, 2 warnings (0.08 sec)
Warning (Code 1264): Out of range value for column 'b' at
row 1
Warning (Code 1264): Out of range value for column 'c' at
row 1
INSERT INTO tinyints VALUES (-10,10,-10);
Query OK, 1 row affected, 1 warning (0.11 sec)
Warning (Code 1264): Out of range value for column 'c' at
row 1
INSERT INTO tinyints VALUES (-10,10,10);
SELECT * FROM tinyints;
+------+------+------+
| a | b | c |
+------+------+------+
| -10 | 0 | 000 |
| -10 | 10 | 000 |
| -10 | 10 | 010 |
+------+------+------+
INSERT INTO tinyints VALUES (128,128,128);
Query OK, 1 row affected, 1 warning (0.19 sec)
Warning (Code 1264): Out of range value for column 'a' at
row 1
INSERT INTO tinyints VALUES (127,128,128);
SELECT * FROM tinyints;
+------+------+------+
| a | b | c |
+------+------+------+
| -10 | 0 | 000 |
| -10 | 10 | 000 |
| -10 | 10 | 010 |
| 127 | 128 | 128 |
| 127 | 128 | 128 |
+------+------+------+
URL: https://mariadb.com/kb/en/tinyint/https://mariadb.com/kb/en/tinyint/ ) �$ VARBINARYSyntax
------
VARBINARY(M)
Description
-----------
The VARBINARY type is similar to the VARCHAR type, but
stores binary byte strings rather than non-binary character
strings. M represents the maximum column length in bytes.
It contains no character set, and comparison and sorting are
based on the numeric value of the bytes.
If the maximum length is exceeded, and SQL strict mode is
not enabled , the extra characters will be dropped with a
warning. If strict mode is enabled, an error will occur.
Unlike BINARY values, VARBINARYs are not right-padded when
inserting.
Oracle Mode
In Oracle mode from MariaDB 10.3, RAW is a synonym for
VARBINARY.
Examples
--------
Inserting too many characters, first with strict mode off,
then with it on:
CREATE TABLE varbins (a VARBINARY(10));
INSERT INTO varbins VALUES('12345678901');
Query OK, 1 row affected, 1 warning (0.04 sec)
SELECT * FROM varbins;
+------------+
| a |
+------------+
| 1234567890 |
+------------+
SET sql_mode='STRICT_ALL_TABLES';
INSERT INTO varbins VALUES('12345678901');
ERROR 1406 (22001): Data too long for column 'a' at row 1
Sorting is performed with the byte value:
TRUNCATE varbins;
INSERT INTO varbins VALUES('A'),('B'),('a'),('b');
SELECT * FROM varbins ORDER BY a;
+------+
| a |
+------+
| A |
| B |
| a |
| b |
+------+
Using CAST to sort as a CHAR instead:
SELECT * FROM varbins ORDER BY CAST(a AS CHAR);
+------+
| a |
+------+
| a |
| A |
| b |
| B |
+------+
URL: https://mariadb.com/kb/en/varbinary/https://mariadb.com/kb/en/varbinary/ E > % ASCIISyntax
------
ASCII(str)
Description
-----------
Returns the numeric ASCII value of the leftmost character of
the string argument. Returns 0 if the given string is empty
and NULL if it is NULL.
ASCII() works for 8-bit characters.
Examples
--------
SELECT ASCII(9);
+----------+
| ASCII(9) |
+----------+
| 57 |
+----------+
SELECT ASCII('9');
+------------+
| ASCII('9') |
+------------+
| 57 |
+------------+
SELECT ASCII('abc');
+--------------+
| ASCII('abc') |
+--------------+
| 97 |
+--------------+
URL: https://mariadb.com/kb/en/ascii/https://mariadb.com/kb/en/ascii/ F � % BINSyntax
------
BIN(N)
Description
-----------
Returns a string representation of the binary value of the
given longlong (that is, BIGINT) number. This is equivalent
to CONV(N,10,2). The argument should be positive. If it is a
FLOAT, it will be truncated. Returns NULL if the argument is
NULL.
Examples
--------
SELECT BIN(12);
+---------+
| BIN(12) |
+---------+
| 1100 |
+---------+
URL: https://mariadb.com/kb/en/bin/https://mariadb.com/kb/en/bin/ H
V% % BIT_LENGTHSyntax
------
BIT_LENGTH(str)
Description
-----------
Returns the length of the given string argument in bits. If
the argument is not a string, it will be converted to
string. If the argument is NULL, it returns NULL.
Examples
--------
SELECT BIT_LENGTH('text');
+--------------------+
| BIT_LENGTH('text') |
+--------------------+
| 32 |
+--------------------+
SELECT BIT_LENGTH('');
+----------------+
| BIT_LENGTH('') |
+----------------+
| 0 |
+----------------+
Compatibility
PostgreSQL and Sybase support BIT_LENGTH().
URL: https://mariadb.com/kb/en/bit_length/https://mariadb.com/kb/en/bit_length/ �7��q�4�
� �
�_N� �� * �" VARCHARSyntax
------
[NATIONAL] VARCHAR(M) [CHARACTER SET charset_name] [COLLATE
collation_name]
Description
-----------
A variable-length string. M represents the maximum column
length in
characters. The range of M is 0 to 65,532. The effective
maximum
length of a VARCHAR is subject to the maximum row size and
the character set used. For
example, utf8 characters can require up to three bytes per
character,
so a VARCHAR column that uses the utf8 character set can be
declared
to be a maximum of 21,844 characters.
MariaDB stores VARCHAR values as a one-byte or two-byte
length prefix
plus data. The length prefix indicates the number of bytes
in the
value. A VARCHAR column uses one length byte if values
require no more
than 255 bytes, two length bytes if values may require more
than 255
bytes.
Note: MariaDB 5.1 and later follow the standard SQL
specification,
and do not remove trailing spaces from VARCHAR values.
VARCHAR(0) columns can contain 2 values: an empty string or
NULL. Such columns cannot be part of an index. The CONNECT
storage engine does not support VARCHAR(0).
VARCHAR is shorthand for CHARACTER VARYING. NATIONAL VARCHAR
is the
standard SQL way to define that a VARCHAR column should use
some
predefined character set. MariaDB uses utf8 as this
predefined character set, as does MySQL 4.1 and up.
NVARCHAR is shorthand for NATIONAL VARCHAR.
Before MariaDB 10.2, all MariaDB collations were of type
PADSPACE, meaning that VARCHAR (as well as CHAR and TEXT
values) are compared without regard for trailing spaces.
This does not apply to the LIKE pattern-matching operator,
which takes into account trailing spaces. From MariaDB 10.2,
a number of NO PAD collations are available.
If a unique index consists of a column where trailing pad
characters are stripped or ignored, inserts into that column
where values differ only by the number of trailing pad
characters will result in a duplicate-key error.
Examples
--------
The following are equivalent:
VARCHAR(30) CHARACTER SET utf8
NATIONAL VARCHAR(30)
NVARCHAR(30)
NCHAR VARCHAR(30)
NATIONAL CHARACTER VARYING(30)
NATIONAL CHAR VARYING(30)
Trailing spaces:
CREATE TABLE strtest (v VARCHAR(10));
INSERT INTO strtest VALUES('Maria ');
SELECT v='Maria',v='Maria ' FROM strtest;
+-----------+--------------+
| v='Maria' | v='Maria ' |
+-----------+--------------+
| 1 | 1 |
+-----------+--------------+
SELECT v LIKE 'Maria',v LIKE 'Maria ' FROM strtest;
+----------------+-------------------+
| v LIKE 'Maria' | v LIKE 'Maria ' |
+----------------+-------------------+
| 0 | 1 |
+----------------+-------------------+
Truncation
Depending on whether or not strict sql mode is set, you will
either get a warning or an error if you try to insert a
string that is too long into a VARCHAR column. If the extra
characters are spaces, the spaces that can't fit will be
removed and you will always get a warning, regardless of the
sql mode setting.
Difference Between VARCHAR and TEXT
VARCHAR columns can be fully indexed. TEXT columns can only
be indexed over a specified length.
Using TEXT or BLOB in a SELECT query that uses temporary
tables for storing intermediate results will force the
temporary table to be disk based (using the Aria storage
engine instead of the memory storage engine, which is a bit
slower. This is not that bad as the Aria storage engine
caches the rows in memory. To get the benefit of this, one
should ensure that the aria_pagecache_buffer_size variable
is big enough to hold most of the row and index data for
temporary tables.
Oracle Mode
In Oracle mode from MariaDB 10.3, VARCHAR2 is a synonym.
For Storage Engine Developers
Internally the full length of the VARCHAR column is
allocated inside each TABLE objects record[] structure. As
there are three such buffers, each open table will allocate
3 times max-length-to-store-varchar bytes of memory.
TEXT and BLOB columns are stored with a pointer (4 or 8
bytes) + a 1-4 bytes length. The TEXT data is only stored
once. This means that internally TEXT uses less memory for
each open table but instead has the additional overhead that
each TEXT object needs to be allocated and freed for each
row access (with some caching in between).
URL: https://mariadb.com/kb/en/varchar/https://mariadb.com/kb/en/varchar/ + � ) YEAR Data TypeSyntax
------
YEAR[(4)]
Description
-----------
A year in two-digit or four-digit format. The default is
four-digit format. Note that the two-digit format has been
deprecated since 5.5.27.
In four-digit format, the allowable values are 1901 to 2155,
and 0000. In two-digit format, the allowable values are 70
to 69,
representing years from 1970 to 2069. MariaDB displays YEAR
values in
YYYY format, but allows you to assign values to YEAR columns
using
either strings or numbers.
Inserting numeric zero has a different result for YEAR(4)
and YEAR(2). For YEAR(2), the value 00 reflects the year
2000. For YEAR(4), the value 0000 reflects the year zero.
This only applies to numeric zero. String zero always
reflects the year 2000.
Examples
--------
Accepting a string or a number:
CREATE TABLE y(y YEAR);
INSERT INTO y VALUES (1990),('2012');
SELECT * FROM y;
+------+
| y |
+------+
| 1990 |
| 2012 |
+------+
Out of range:
INSERT INTO y VALUES (1005),('3080');
Query OK, 2 rows affected, 2 warnings (0.05 sec)
Records: 2 Duplicates: 0 Warnings: 2
SHOW WARNINGS;
+---------+------+--------------------------------------------+
| Level | Code | Message |
+---------+------+--------------------------------------------+
| Warning | 1264 | Out of range value for column 'y' at
row 1 |
| Warning | 1264 | Out of range value for column 'y' at
row 2 |
+---------+------+--------------------------------------------+
SELECT * FROM y;
+------+
| y |
+------+
| 1990 |
| 2012 |
| 0000 |
| 0000 |
+------+
Truncating:
INSERT INTO y VALUES ('2013-12-12');
Query OK, 1 row affected, 1 warning (0.05 sec)
SHOW WARNINGS;
+---------+------+----------------------------------------+
| Level | Code | Message |
+---------+------+----------------------------------------+
| Warning | 1265 | Data truncated for column 'y' at row 1
|
+---------+------+----------------------------------------+
SELECT * FROM y;
+------+
| y |
+------+
| 1990 |
| 2012 |
| 0000 |
| 0000 |
| 2013 |
+------+
Difference between YEAR(2) and YEAR(4), and string and
numeric zero:
CREATE TABLE y2(y YEAR(4), y2 YEAR(2));
Query OK, 0 rows affected, 1 warning (0.40 sec)
Note (Code 1287): 'YEAR(2)' is deprecated and will be
removed in a future release. Please use YEAR(4) instead
INSERT INTO y2 VALUES(0,0),('0','0');
SELECT YEAR(y),YEAR(y2) FROM y;
+---------+----------+
| YEAR(y) | YEAR(y2) |
+---------+----------+
| 0 | 2000 |
| 2000 | 2000 |
+---------+----------+
URL: https://mariadb.com/kb/en/year-data-type/https://mariadb.com/kb/en/year-data-type/ K � + % CHARACTER_LENGTHSyntax
------
CHARACTER_LENGTH(str)
Description
-----------
CHARACTER_LENGTH() is a synonym for CHAR_LENGTH().
URL: https://mariadb.com/kb/en/character_length/https://mariadb.com/kb/en/character_length/ Z � % INSTRSyntax
------
INSTR(str,substr)
Description
-----------
Returns the position of the first occurrence of substring
substr in
string str. This is the same as the two-argument form of
LOCATE(),
except that the order of the arguments is reversed.
INSTR() performs a case-insensitive search.
If any argument is NULL, returns NULL.
Examples
--------
SELECT INSTR('foobarbar', 'bar');
+---------------------------+
| INSTR('foobarbar', 'bar') |
+---------------------------+
| 4 |
+---------------------------+
SELECT INSTR('My', 'Maria');
+----------------------+
| INSTR('My', 'Maria') |
+----------------------+
| 0 |
+----------------------+
URL: https://mariadb.com/kb/en/instr/https://mariadb.com/kb/en/instr/ � � �
�1H �� , 9
$ BEGIN ENDSyntax
------
[begin_label:] BEGIN [NOT ATOMIC]
[statement_list]
END [end_label]
NOT ATOMIC is required when used outside of a stored
procedure. Inside stored procedures or within an anonymous
block, BEGIN alone starts a new anonymous block.
Description
-----------
BEGIN ... END syntax is used for writing compound
statements. A compound statement can contain multiple
statements, enclosed by the BEGIN and END keywords.
statement_list represents a list of one or more statements,
each
terminated by a semicolon (i.e., ;) statement delimiter.
statement_list is
optional, which means that the empty compound statement
(BEGIN END) is
legal.
Note that END will perform a commit. If you are running in
autocommit mode, every statement will be committed
separately. If you are not running in autocommit mode, you
must execute a COMMIT or ROLLBACK after END to get the
database up to date.
Use of multiple statements requires that a client is able to
send statement strings containing the ; statement delimiter.
This is handled in the mysql command-line client with the
DELIMITER command.
Changing the ; end-of-statement delimiter (for example, to
//) allows ; to be used in a program body.
A compound statement within a stored program can be
labeled. end_label cannot be given unless begin_label also
is present. If both are present, they must be the same.
BEGIN ... END constructs can be nested. Each block can
define its own variables, a CONDITION, a HANDLER and a
CURSOR, which don't exist in the outer blocks. The most
local declarations override the outer objects which use the
same name (see example below).
The declarations order is the following:
DECLARE local variables;
DECLARE CONDITIONs;
DECLARE CURSORs;
DECLARE HANDLERs;
Note that DECLARE HANDLER contains another BEGIN ... END
construct.
Here is an example of a very simple, anonymous block:
BEGIN NOT ATOMIC
SET @a=1;
CREATE TABLE test.t1(a INT);
END|
Below is an example of nested blocks in a stored procedure:
CREATE PROCEDURE t( )
BEGIN
DECLARE x TINYINT UNSIGNED DEFAULT 1;
BEGIN
DECLARE x CHAR(2) DEFAULT '02';
DECLARE y TINYINT UNSIGNED DEFAULT 10;
SELECT x, y;
END;
SELECT x;
END;
In this example, a TINYINT variable, x is declared in the
outter block. But in the inner block x is re-declared as a
CHAR and an y variable is declared. The inner SELECT shows
the "new" value of x, and the value of y. But when x is
selected in the outer block, the "old" value is returned.
The final SELECT doesn't try to read y, because it doesn't
exist in that context.
URL: https://mariadb.com/kb/en/begin-end/https://mariadb.com/kb/en/begin-end/ - �) CASE StatementSyntax
------
CASE case_value
WHEN when_value THEN statement_list
[WHEN when_value THEN statement_list] ...
[ELSE statement_list]
END CASE
Or:
CASE
WHEN search_condition THEN statement_list
[WHEN search_condition THEN statement_list] ...
[ELSE statement_list]
END CASE
Description
-----------
The CASE statement for stored programs implements a complex
conditional
construct. If a search_condition evaluates to true, the
corresponding SQL
statement list is executed. If no search condition matches,
the statement list
in the ELSE clause is executed. Each statement_list consists
of one or
more statements.
If no when_value or search_condition matches the value
tested and the CASE
statement contains no ELSE clause, a Case not found for CASE
statement
error results.
Each statement_list consists of one or more statements; an
empty
statement_list is not allowed. To handle situations where no
value is
matched by any WHEN clause, use an ELSE containing an
empty BEGIN ... END block, as shown in this example:
DELIMITER |
CREATE PROCEDURE p()
BEGIN
DECLARE v INT DEFAULT 1;
CASE v
WHEN 2 THEN SELECT v;
WHEN 3 THEN SELECT 0;
ELSE BEGIN END;
END CASE;
END;
|
The indentation used here in the ELSE clause is for purposes
of clarity only,
and is not otherwise significant. See Delimiters in the
mysql client for more on the use of the delimiter command.
Note: The syntax of the CASE statement used inside stored
programs
differs slightly from that of the SQL CASE expression
described in
CASE OPERATOR.
The CASE statement cannot have an ELSE NULL clause, and it
is
terminated with END CASE instead of END.
URL: https://mariadb.com/kb/en/case-statement/https://mariadb.com/kb/en/case-statement/ / ^, DECLARE CONDITIONSyntax
------
DECLARE condition_name CONDITION FOR condition_value
condition_value:
SQLSTATE [VALUE] sqlstate_value
| mysql_error_code
Description
-----------
The DECLARE ... CONDITION statement defines a named error
condition.
It specifies a condition that needs specific handling and
associates a
name with that condition. Later, the name can be used in a
DECLARE ... HANDLER, SIGNAL or RESIGNAL statement (as long
as the statement is located in the same BEGIN ... END
block).
Conditions must be declared after local variables, but
before CURSORs and HANDLERs.
A condition_value for DECLARE ... CONDITION can be an
SQLSTATE value (a
5-character string literal) or a MySQL error code (a
number). You should not
use SQLSTATE value '00000' or MySQL error code 0, because
those indicate sucess
rather than an error condition. If you try, or if you
specify an invalid SQLSTATE value, an error like this is
produced:
ERROR 1407 (42000): Bad SQLSTATE: '00000'
For a list of SQLSTATE values and MariaDB error
codes, see MariaDB Error Codes.
URL: https://mariadb.com/kb/en/declare-condition/https://mariadb.com/kb/en/declare-condition/ [ � % LCASESyntax
------
LCASE(str)
Description
-----------
LCASE() is a synonym for LOWER().
URL: https://mariadb.com/kb/en/lcase/https://mariadb.com/kb/en/lcase/ \ ^ % LEFTSyntax
------
LEFT(str,len)
Description
-----------
Returns the leftmost len characters from the string str, or
NULL if
any argument is NULL.
Examples
--------
SELECT LEFT('MariaDB', 5);
+--------------------+
| LEFT('MariaDB', 5) |
+--------------------+
| Maria |
+--------------------+
URL: https://mariadb.com/kb/en/left/https://mariadb.com/kb/en/left/ ^ � " % LENGTHBIntroduced in MariaDB 10.3.1 as part of the Oracle
compatibility enhancements.
Syntax
------
LENGTHB(str)
Description
-----------
LENGTHB() is a synonym for LENGTH().
URL: https://mariadb.com/kb/en/lengthb/https://mariadb.com/kb/en/lengthb/ g 4 % MIDSyntax
------
MID(str,pos,len)
Description
-----------
MID(str,pos,len) is a synonym for SUBSTRING(str,pos,len).
Examples
--------
SELECT MID('abcd',4,1);
+-----------------+
| MID('abcd',4,1) |
+-----------------+
| d |
+-----------------+
SELECT MID('abcd',2,2);
+-----------------+
| MID('abcd',2,2) |
+-----------------+
| bc |
+-----------------+
A negative starting position:
SELECT MID('abcd',-2,4);
+------------------+
| MID('abcd',-2,4) |
+------------------+
| cd |
+------------------+
URL: https://mariadb.com/kb/en/mid/https://mariadb.com/kb/en/mid/ h � # % NOT LIKESyntax
------
expr NOT LIKE pat [ESCAPE 'escape_char']
Description
-----------
This is the same as NOT (expr LIKE pat [ESCAPE
'escape_char']).
URL: https://mariadb.com/kb/en/not-like/https://mariadb.com/kb/en/not-like/ ��ck ��� r��
� t
��'� � 1 �* DECLARE HANDLERSyntax
------
DECLARE handler_type HANDLER
FOR condition_value [, condition_value] ...
statement
handler_type:
CONTINUE
| EXIT
| UNDO
condition_value:
SQLSTATE [VALUE] sqlstate_value
| condition_name
| SQLWARNING
| NOT FOUND
| SQLEXCEPTION
| mariadb_error_code
Description
-----------
The DECLARE ... HANDLER statement specifies handlers that
each may
deal with one or more conditions. If one of these conditions
occurs,
the specified statement is executed. statement can be a
simple
statement (for example, SET var_name = value), or it can be
a compound
statement written using BEGIN and END.
Handlers must be declared after local variables, a CONDITION
and a CURSOR.
For a CONTINUE handler, execution of the current program
continues
after execution of the handler statement. For an EXIT
handler,
execution terminates for the BEGIN ... END compound
statement in which
the handler is declared. (This is true even if the condition
occurs in
an inner block.) The UNDO handler type statement is not
supported.
If a condition occurs for which no handler has been
declared, the
default action is EXIT.
A condition_value for DECLARE ... HANDLER can be any of the
following
values:
An SQLSTATE value (a 5-character string literal) or a
MariaDB error
code (a number). You should not use SQLSTATE value '00000'
or MariaDB
error code 0, because those indicate sucess rather than an
error
condition. For a list of SQLSTATE values and MariaDB error
codes, see
MariaDB Error Codes.
A condition name previously specified with DECLARE ...
CONDITION. It must be in the same stored program. See
DECLARE CONDITION.
SQLWARNING is shorthand for the class of SQLSTATE values
that begin
with '01'.
NOT FOUND is shorthand for the class of SQLSTATE values that
begin
with '02'. This is relevant only the context of cursors
and is used to
control what happens when a cursor reaches the end of a data
set. If
no more rows are available, a No Data condition occurs with
SQLSTATE
value 02000. To detect this condition, you can set up a
handler for it
(or for a NOT FOUND condition). An example is shown in
Cursor Overview. This condition also occurs for SELECT ...
INTO var_list statements that retrieve no
rows.
SQLEXCEPTION is shorthand for the class of SQLSTATE values
that do
not begin with '00', '01', or '02'.
When an error raises, in some cases it could be handled by
multiple HANDLERs. For example, there may be an handler for
1050 error, a separate handler for the 42S01 SQLSTATE, and
another separate handler for the SQLEXCEPTION class: in
theory all occurrences of HANDLER may catch the 1050 error,
but MariaDB chooses the HANDLER with the highest precedence.
Here are the precedence rules:
Handlers which refer to an error code have the highest
precedence.
Handlers which refer to a SQLSTATE come next.
Handlers which refer to an error class have the lowest
precedence.
In some cases, a statement could produce multiple errors. If
this happens, in some cases multiple handlers could have the
highest precedence. In such cases, the choice of the handler
is indeterminate.
Note that if an error occurs within a CONTINUE HANDLER
block, it can be handled by another HANDLER. However, a
HANDLER which is already in the stack (that is, it has been
called to handle an error and its execution didn't finish
yet) cannot handle new errors—this prevents endless loops.
For example, suppose that a stored procedure contains a
CONTINUE HANDLER for SQLWARNING and another CONTINUE HANDLER
for NOT FOUND. At some point, a NOT FOUND error occurs, and
the execution enters the NOT FOUND HANDLER. But within that
handler, a warning occurs, and the execution enters the
SQLWARNING HANDLER. If another NOT FOUND error occurs, it
cannot be handled again by the NOT FOUND HANDLER, because
its execution is not finished.
When a DECLARE HANDLER block can handle more than one error
condition, it may be useful to know which errors occurred.
To do so, you can use the GET DIAGNOSTICS statement.
An error that is handled by a DECLARE HANDLER construct can
be issued again using the RESIGNAL statement.
Below is an example using DECLARE HANDLER:
CREATE TABLE test.t (s1 INT, PRIMARY KEY (s1));
DELIMITER //
CREATE PROCEDURE handlerdemo ( )
BEGIN
DECLARE CONTINUE HANDLER FOR SQLSTATE '23000' SET @x2 =
1;
SET @x = 1;
INSERT INTO test.t VALUES (1);
SET @x = 2;
INSERT INTO test.t VALUES (1);
SET @x = 3;
END;
//
DELIMITER ;
CALL handlerdemo( );
SELECT @x;
+------+
| @x |
+------+
| 3 |
+------+
URL: https://mariadb.com/kb/en/declare-handler/https://mariadb.com/kb/en/declare-handler/ 2 M + DECLARE VariableSyntax
------
DECLARE var_name [, var_name] ... [[ROW] TYPE OF]] type
[DEFAULT value]
Description
-----------
This statement is used to declare local variables within
stored programs. To
provide a default value for the variable, include a DEFAULT
clause. The
value can be specified as an expression (even subqueries are
permitted); it need not be a constant. If the
DEFAULT clause is missing, the initial value is NULL.
Local variables are treated like stored routine parameters
with respect to data
type and overflow checking. See CREATE PROCEDURE.
Local variables must be declared before CONDITIONs, CURSORs
and HANDLERs.
Local variable names are not case sensitive.
The scope of a local variable is within the BEGIN ... END
block where it is
declared. The variable can be referred to in blocks nested
within the declaring
block, except those blocks that declare a variable with the
same name.
TYPE OF / ROW TYPE OF
TYPE OF and ROW TYPE OF anchored data types for stored
routines were introduced in MariaDB 10.3.
Anchored data types allow a data type to be defined based on
another object, such as a table row, rather than
specifically set in the declaration. If the anchor object
changes, so will the anchored data type. This can lead to
routines being easier to maintain, so that if the data type
in the table is changed, it will automatically be changed in
the routine as well.
Variables declared with ROW TYPE OF will have the same
features as implicit ROW variables. It is not possible to
use ROW TYPE OF variables in a LIMIT clause.
The real data type of TYPE OF and ROW TYPE OF table_name
will become known at the very beginning of the stored
routine call. ALTER TABLE or DROP TABLE statements performed
inside the current routine on the tables that appear in
anchors won't affect the data type of the anchored
variables, even if the variable is declared after an ALTER
TABLE or DROP TABLE statement.
The real data type of a ROW TYPE OF cursor_name variable
will become known when execution enters into the block where
the variable is declared. Data type instantiation will
happen only once. In a cursor ROW TYPE OF variable that is
declared inside a loop, its data type will become known on
the very first iteration and won't change on further loop
iterations.
The tables referenced in TYPE OF and ROW TYPE OF
declarations will be checked for existence at the beginning
of the stored routine call. CREATE PROCEDURE or CREATE
FUNCTION will not check the referenced tables for existence.
Examples
--------
TYPE OF and ROW TYPE OF from MariaDB 10.3:
DECLARE tmp TYPE OF t1.a;
-- Get the data type from the column {{a}} in the table
{{t1}}
DECLARE rec1 ROW TYPE OF t1;
-- Get the row data type from the table {{t1}}
DECLARE rec2 ROW TYPE OF cur1;
-- Get the row data type from the cursor {{cur1}}
URL: https://mariadb.com/kb/en/declare-variable/https://mariadb.com/kb/en/declare-variable/ E� 9�\Uz �w 4 X
FORFOR loops were introduced in MariaDB 10.3.
Syntax
------
Integer range FOR loop:
[begin_label:]
FOR var_name IN [ REVERSE ] lower_bound .. upper_bound
DO statement_list
END FOR [ end_label ]
Explicit cursor FOR loop
[begin_label:]
FOR record_name IN cursor_name [ (
cursor_actual_parameter_list)]
DO statement_list
END FOR [ end_label ]
Explicit cursor FOR loop (Oracle mode)
[begin_label:]
FOR record_name IN cursor_name [ (
cursor_actual_parameter_list)]
LOOP
statement_list
END LOOP [ end_label ]
Implicit cursor FOR loop
[begin_label:]
FOR record_name IN ( select_statement )
DO statement_list
END FOR [ end_label ]
Description
-----------
FOR loops allow code to be executed a fixed number of times.
In an integer range FOR loop, MariaDB will compare the lower
bound and upper bound values, and assign the lower bound
value to a counter. If REVERSE is not specified, and the
upper bound value is greater than or equal to the counter,
the counter will be incremented and the statement will
continue, after which the loop is entered again. If the
upper bound value is greater than the counter, the loop will
be exited.
If REVERSE is specified, the counter is decremented, and the
upper bound value needs to be less than or equal for the
loop to continue.
Examples
--------
Intger range FOR loop:
CREATE TABLE t1 (a INT);
DELIMITER //
FOR i IN 1..3
DO
INSERT INTO t1 VALUES (i);
END FOR;
//
DELIMITER ;
SELECT * FROM t1;
+------+
| a |
+------+
| 1 |
| 2 |
| 3 |
+------+
REVERSE integer range FOR loop:
CREATE OR REPLACE TABLE t1 (a INT);
DELIMITER //
FOR i IN REVERSE 12..4
DO
INSERT INTO t1 VALUES (i);
END FOR;
//
Query OK, 9 rows affected (0.422 sec)
DELIMITER ;
SELECT * FROM t1;
+------+
| a |
+------+
| 12 |
| 11 |
| 10 |
| 9 |
| 8 |
| 7 |
| 6 |
| 5 |
| 4 |
+------+
Explicit cursor in Oracle mode:
SET sql_mode=ORACLE;
CREATE OR REPLACE TABLE t1 (a INT, b VARCHAR(32));
INSERT INTO t1 VALUES (10,'b0');
INSERT INTO t1 VALUES (11,'b1');
INSERT INTO t1 VALUES (12,'b2');
DELIMITER //
CREATE OR REPLACE PROCEDURE p1(pa INT) AS
CURSOR cur(va INT) IS
SELECT a, b FROM t1 WHERE a=va;
BEGIN
FOR rec IN cur(pa)
LOOP
SELECT rec.a, rec.b;
END LOOP;
END;
//
DELIMITER ;
CALL p1(10);
+-------+-------+
| rec.a | rec.b |
+-------+-------+
| 10 | b0 |
+-------+-------+
CALL p1(11);
+-------+-------+
| rec.a | rec.b |
+-------+-------+
| 11 | b1 |
+-------+-------+
CALL p1(12);
+-------+-------+
| rec.a | rec.b |
+-------+-------+
| 12 | b2 |
+-------+-------+
CALL p1(13);
Query OK, 0 rows affected (0.000 sec)
URL: https://mariadb.com/kb/en/for/https://mariadb.com/kb/en/for/ 8 ! LabelsSyntax
------
label:
[label]
Labels are MariaDB identifiers which can be used to identify
a BEGIN ... END construct or a loop. They have a maximum
length of 16 characters and can be quoted with backticks
(i.e.., `).
Labels have a start part and an end part. The start part
must precede the portion of code it refers to, must be
followed by a colon (:) and can be on the same or different
line. The end part is optional and adds nothing, but can
make the code more readable. If used, the end part must
precede the construct's delimiter (;). Constructs
identified by a label can be nested. Each construct can be
identified by only one label.
Labels need not be unique in the stored program they belong
to. However, a label for an inner loop cannot be identical
to a label for an outer loop. In this case, the following
error would be produced:
ERROR 1309 (42000): Redefining label
LEAVE and ITERATE statements can be used to exit or repeat a
portion of code identified by a label. They must be in the
same Stored Routine, Trigger or Event which contains the
target label.
Below is an example using a simple label that is used to
exit a LOOP:
CREATE PROCEDURE `test_sp`()
BEGIN
`my_label`:
LOOP
SELECT 'looping';
LEAVE `my_label`;
END LOOP;
SELECT 'out of loop';
END;
The following label is used to exit a procedure, and has an
end part:
CREATE PROCEDURE `test_sp`()
`my_label`:
BEGIN
IF @var = 1 THEN
LEAVE `my_label`;
END IF;
DO something();
END `my_label`;
URL: https://mariadb.com/kb/en/labels/https://mariadb.com/kb/en/labels/ 9 � LEAVESyntax
------
LEAVE label
This statement is used to exit the flow control construct
that has the
given label. The label must be in the same stored program,
not in a caller procedure. LEAVE can be used within BEGIN
... END or loop constructs
(LOOP, REPEAT, WHILE). In Stored Procedures, Triggers and
Events, LEAVE can refer to the outmost BEGIN ... END
construct; in that case, the program exits the procedure. In
Stored Functions, RETURN can be used instead.
Note that LEAVE cannot be used to exit a DECLARE HANDLER
block.
If you try to LEAVE a non-existing label, or if you try to
LEAVE a HANDLER block, the following error will be produced:
ERROR 1308 (42000): LEAVE with no matching label:
The following example uses LEAVE to exit the procedure if a
condition is true:
CREATE PROCEDURE proc(IN p TINYINT)
CONTAINS SQL
`whole_proc`:
BEGIN
SELECT 1;
IF p
URL: https://mariadb.com/kb/en/leave/https://mariadb.com/kb/en/leave/ i
� % % NOT REGEXPSyntax
------
expr NOT REGEXP pat, expr NOT RLIKE pat
Description
-----------
This is the same as NOT (expr REGEXP pat).
URL: https://mariadb.com/kb/en/not-regexp/https://mariadb.com/kb/en/not-regexp/ j (' % OCTET_LENGTHSyntax
------
OCTET_LENGTH(str)
Description
-----------
OCTET_LENGTH() is normally a synonym for LENGTH(). When
running Oracle mode from MariaDB 10.3, they are not
synonyms, but OCTET_LENGTH() behaves as LENGTH() would when
not in Oracle mode.
URL: https://mariadb.com/kb/en/octet_length/https://mariadb.com/kb/en/octet_length/ k 5 % ORDSyntax
------
ORD(str)
Description
-----------
If the leftmost character of the string str is a multi-byte
character,
returns the code for that character, calculated from the
numeric
values of its constituent bytes using this formula:
(1st byte code)
+ (2nd byte code x 256)
+ (3rd byte code x 256 x 256) ...
If the leftmost character is not a multi-byte character,
ORD() returns
the same value as the ASCII() function.
Examples
--------
SELECT ORD('2');
+----------+
| ORD('2') |
+----------+
| 50 |
+----------+
URL: https://mariadb.com/kb/en/ord/https://mariadb.com/kb/en/ord/ l � # % POSITIONSyntax
------
POSITION(substr IN str)
Description
-----------
POSITION(substr IN str) is a synonym for LOCATE(substr,str).
It's part of ODBC 3.0.
URL: https://mariadb.com/kb/en/position/https://mariadb.com/kb/en/position/ m � % QUOTESyntax
------
QUOTE(str)
Description
-----------
Quotes a string to produce a result that can be used as a
properly escaped data
value in an SQL statement. The string is returned enclosed
by single quotes and
with each instance of single quote ("'"), backslash
("\"),
ASCII NUL, and Control-Z preceded by a backslash. If the
argument
is NULL, the return value is the word "NULL" without
enclosing single
quotes.
Examples
--------
SELECT QUOTE("Don't!");
+-----------------+
| QUOTE("Don't!") |
+-----------------+
| 'Don\'t!' |
+-----------------+
SELECT QUOTE(NULL);
+-------------+
| QUOTE(NULL) |
+-------------+
| NULL |
+-------------+
URL: https://mariadb.com/kb/en/quote/https://mariadb.com/kb/en/quote/ p�e d�i�� ���
K �
rQ� �J < U& REPEAT LOOPSyntax
------
[begin_label:] REPEAT
statement_list
UNTIL search_condition
END REPEAT [end_label]
The statement list within a REPEAT statement is repeated
until the
search_condition is true. Thus, a REPEAT always enters the
loop at
least once. statement_list consists of one or more
statements, each
terminated by a semicolon (i.e., ;) statement delimiter.
A REPEAT statement can be labeled. end_label cannot be given
unless
begin_label also is present. If both are present, they must
be the
same.
See Delimiters in the mysql client for more on client
delimiter usage.
DELIMITER //
CREATE PROCEDURE dorepeat(p1 INT)
BEGIN
SET @x = 0;
REPEAT SET @x = @x + 1;
UNTIL @x > p1 END REPEAT;
END
//
CALL dorepeat(1000)//
SELECT @x//
+------+
| @x |
+------+
| 1001 |
+------+
URL: https://mariadb.com/kb/en/repeat-loop/https://mariadb.com/kb/en/repeat-loop/ = | # RESIGNALSyntax
------
RESIGNAL [error_condition]
[SET error_property
[, error_property] ...]
error_condition:
SQLSTATE [VALUE] 'sqlstate_value'
| condition_name
error_property:
error_property_name =
error_property_name:
CLASS_ORIGIN
| SUBCLASS_ORIGIN
| MESSAGE_TEXT
| MYSQL_ERRNO
| CONSTRAINT_CATALOG
| CONSTRAINT_SCHEMA
| CONSTRAINT_NAME
| CATALOG_NAME
| SCHEMA_NAME
| TABLE_NAME
| COLUMN_NAME
| CURSOR_NAME
Description
-----------
The syntax of RESIGNAL and its semantics are very similar to
SIGNAL. This statement can only be used within an error
HANDLER. It produces an error, like SIGNAL. RESIGNAL clauses
are the same as SIGNAL, except that they all are optional,
even SQLSTATE. All the properties which are not specified in
RESIGNAL, will be identical to the properties of the error
that was received by the error HANDLER. For a description of
the clauses, see diagnostics area.
Note that RESIGNAL does not empty the diagnostics area: it
just appends another error condition.
RESIGNAL, without any clauses, produces an error which is
identical to the error that was received by HANDLER.
If used out of a HANDLER construct, RESIGNAL produces the
following error:
ERROR 1645 (0K000): RESIGNAL when handler not active
In MariaDB 5.5, if a HANDLER contained a CALL to another
procedure, that procedure could use RESIGNAL. Since MariaDB
10.0, trying to do this raises the above error.
For a list of SQLSTATE values and MariaDB error codes, see
MariaDB Error Codes.
The following procedure tries to query two tables which
don't exist, producing a 1146 error in both cases. Those
errors will trigger the HANDLER. The first time the error
will be ignored and the client will not receive it, but the
second time, the error is re-signaled, so the client will
receive it.
CREATE PROCEDURE test_error( )
BEGIN
DECLARE CONTINUE HANDLER
FOR 1146
BEGIN
IF @hide_errors IS FALSE THEN
RESIGNAL;
END IF;
END;
SET @hide_errors = TRUE;
SELECT 'Next error will be ignored' AS msg;
SELECT `c` FROM `temptab_one`;
SELECT 'Next error won''t be ignored' AS msg;
SET @hide_errors = FALSE;
SELECT `c` FROM `temptab_two`;
END;
CALL test_error( );
+----------------------------+
| msg |
+----------------------------+
| Next error will be ignored |
+----------------------------+
+-----------------------------+
| msg |
+-----------------------------+
| Next error won't be ignored |
+-----------------------------+
ERROR 1146 (42S02): Table 'test.temptab_two' doesn't
exist
The following procedure re-signals an error, modifying only
the error message to clarify the cause of the problem.
CREATE PROCEDURE test_error()
BEGIN
DECLARE CONTINUE HANDLER
FOR 1146
BEGIN
RESIGNAL SET
MESSAGE_TEXT = '`temptab` does not exist';
END;
SELECT `c` FROM `temptab`;
END;
CALL test_error( );
ERROR 1146 (42S02): `temptab` does not exist
As explained above, this works on MariaDB 5.5, but produces
a 1645 error since 10.0.
CREATE PROCEDURE handle_error()
BEGIN
RESIGNAL;
END;
CREATE PROCEDURE p()
BEGIN
DECLARE EXIT HANDLER FOR SQLEXCEPTION CALL p();
SIGNAL SQLSTATE '45000';
END;
URL: https://mariadb.com/kb/en/resignal/https://mariadb.com/kb/en/resignal/ ? % SELECT INTOSyntax
------
SELECT col_name [, col_name] ...
INTO var_name [, var_name] ...
table_expr
Description
-----------
SELECT ... INTO enables selected columns to be stored
directly
into variables. No resultset is produced. The query should
return a single row. If the query
returns no rows, a warning with error code 1329 occurs (No
data), and
the variable values remain unchanged. If the query returns
multiple
rows, error 1172 occurs (Result consisted of more than one
row). If it
is possible that the statement may retrieve multiple rows,
you can use
LIMIT 1 to limit the result set to a single row.
The INTO clause can also be specified at the end of the
statement.
In the context of such statements that occur as part of
events
executed by the Event Scheduler, diagnostics messages (not
only
errors, but also warnings) are written to the error log,
and, on
Windows, to the application event log.
This statement can be used with both local variables and
user-defined variables.
For the complete syntax, see SELECT.
Another way to set a variable's value is the SET statement.
SELECT ... INTO results are not stored in the query cache
even if SQL_CACHE is specified.
Examples
--------
SELECT id, data INTO @x,@y
FROM test.t1 LIMIT 1;
URL: https://mariadb.com/kb/en/selectinto/https://mariadb.com/kb/en/selectinto/ q * % REPEAT FunctionSyntax
------
REPEAT(str,count)
Description
-----------
Returns a string consisting of the string str repeated count
times. If
count is less than 1, returns an empty string. Returns NULL
if str or
count are NULL.
Examples
--------
SELECT QUOTE(REPEAT('MariaDB ',4));
+------------------------------------+
| QUOTE(REPEAT('MariaDB ',4)) |
+------------------------------------+
| 'MariaDB MariaDB MariaDB MariaDB ' |
+------------------------------------+
URL: https://mariadb.com/kb/en/repeat-function/https://mariadb.com/kb/en/repeat-function/ r 4+ % REPLACE FunctionSyntax
------
REPLACE(str,from_str,to_str)
Description
-----------
Returns the string str with all occurrences of the string
from_str
replaced by the string to_str. REPLACE() performs a
case-sensitive
match when searching for from_str.
Examples
--------
SELECT REPLACE('www.mariadb.org', 'w', 'Ww');
+---------------------------------------+
| REPLACE('www.mariadb.org', 'w', 'Ww') |
+---------------------------------------+
| WwWwWw.mariadb.org |
+---------------------------------------+
URL: https://mariadb.com/kb/en/replace-function/https://mariadb.com/kb/en/replace-function/ s P" % REVERSESyntax
------
REVERSE(str)
Description
-----------
Returns the string str with the order of the characters
reversed.
Examples
--------
SELECT REVERSE('desserts');
+---------------------+
| REVERSE('desserts') |
+---------------------+
| stressed |
+---------------------+
URL: https://mariadb.com/kb/en/reverse/https://mariadb.com/kb/en/reverse/ t c % RIGHTSyntax
------
RIGHT(str,len)
Description
-----------
Returns the rightmost len characters from the string str, or
NULL if
any argument is NULL.
Examples
--------
SELECT RIGHT('MariaDB', 2);
+---------------------+
| RIGHT('MariaDB', 2) |
+---------------------+
| DB |
+---------------------+
URL: https://mariadb.com/kb/en/right/https://mariadb.com/kb/en/right/ �y��}�VUQ�� � � �z @ �! SIGNALSyntax
------
SIGNAL error_condition
[SET error_property
[, error_property] ...]
error_condition:
SQLSTATE [VALUE] 'sqlstate_value'
| condition_name
error_property:
error_property_name =
error_property_name:
CLASS_ORIGIN
| SUBCLASS_ORIGIN
| MESSAGE_TEXT
| MYSQL_ERRNO
| CONSTRAINT_CATALOG
| CONSTRAINT_SCHEMA
| CONSTRAINT_NAME
| CATALOG_NAME
| SCHEMA_NAME
| TABLE_NAME
| COLUMN_NAME
| CURSOR_NAME
SIGNAL empties the diagnostics area and produces a custom
error. This statement can be used anywhere, but is generally
useful when used inside a stored program. When the error is
produced, it can be caught by a HANDLER. If not, the current
stored program, or the current statement, will terminate
with the specified error.
Sometimes an error HANDLER just needs to SIGNAL the same
error it received, optionally with some changes. Usually the
RESIGNAL statement is the most convenient way to do this.
error_condition can be an SQLSTATE value or a named error
condition defined via DECLARE CONDITION. SQLSTATE must be a
constant string consisting of five characters. These codes
are standard to ODBC and ANSI SQL. For customized errors,
the recommended SQLSTATE is '45000'. For a list of
SQLSTATE values used by MariaDB, see the MariaDB Error Codes
page. The SQLSTATE can be read via the API method
mysql_sqlstate( ).
To specify error properties user-defined variables and local
variables can be used, as well as character set conversions
(but you can't set a collation).
The error properties, their type and their default values
are explained in the diagnostics area page.
Errors
If the SQLSTATE is not valid, the following error like this
will be produced:
ERROR 1407 (42000): Bad SQLSTATE: '123456'
If a property is specified more than once, an error like
this will be produced:
ERROR 1641 (42000): Duplicate condition information item
'MESSAGE_TEXT'
If you specify a condition name which is not declared, an
error like this will be produced:
ERROR 1319 (42000): Undefined CONDITION: cond_name
If MYSQL_ERRNO is out of range, you will get an error like
this:
ERROR 1231 (42000): Variable 'MYSQL_ERRNO' can't be set
to the value of '0'
Examples
--------
Here's what happens if SIGNAL is used in the client to
generate errors:
SIGNAL SQLSTATE '01000';
Query OK, 0 rows affected, 1 warning (0.00 sec)
SHOW WARNINGS;
+---------+------+------------------------------------------+
| Level | Code | Message |
+---------+------+------------------------------------------+
| Warning | 1642 | Unhandled user-defined warning condition
|
+---------+------+------------------------------------------+
1 row in set (0.06 sec)
SIGNAL SQLSTATE '02000';
ERROR 1643 (02000): Unhandled user-defined not found
condition
How to specify MYSQL_ERRNO and MESSAGE_TEXT properties:
SIGNAL SQLSTATE '45000' SET MYSQL_ERRNO=30001,
MESSAGE_TEXT='H
ello, world!';
ERROR 30001 (45000): Hello, world!
The following code shows how to use user variables, local
variables and character set conversion with SIGNAL:
CREATE PROCEDURE test_error(x INT)
BEGIN
DECLARE errno SMALLINT UNSIGNED DEFAULT 31001;
SET @errmsg = 'Hello, world!';
IF x = 1 THEN
SIGNAL SQLSTATE '45000' SET
MYSQL_ERRNO = errno,
MESSAGE_TEXT = @errmsg;
ELSE
SIGNAL SQLSTATE '45000' SET
MYSQL_ERRNO = errno,
MESSAGE_TEXT = _utf8'Hello, world!';
END IF;
END;
How to use named error conditions:
CREATE PROCEDURE test_error(n INT)
BEGIN
DECLARE `too_big` CONDITION FOR SQLSTATE '45000';
IF n > 10 THEN
SIGNAL `too_big`;
END IF;
END;
In this example, we'll define a HANDLER for an error code.
When the error occurs, we SIGNAL a more informative error
which makes sense for our procedure:
CREATE PROCEDURE test_error()
BEGIN
DECLARE EXIT HANDLER
FOR 1146
BEGIN
SIGNAL SQLSTATE '45000' SET
MESSAGE_TEXT = 'Temporary tables not found; did you call
init() procedure?';
END;
-- this will produce a 1146 error
SELECT `c` FROM `temptab`;
END;
URL: https://mariadb.com/kb/en/signal/https://mariadb.com/kb/en/signal/ E
e% LINESTRINGSyntax
------
LineString(pt1,pt2,...)
Description
-----------
Constructs a WKB LineString value from a number of WKB Point
arguments. If any argument is not a WKB Point, the return
value is
NULL. If the number of Point arguments is less than two, the
return value is NULL.
Examples
--------
SET @ls = 'LineString(1 1,2 2,3 3)';
SELECT AsText(EndPoint(GeomFromText(@ls)));
+-------------------------------------+
| AsText(EndPoint(GeomFromText(@ls))) |
+-------------------------------------+
| POINT(3 3) |
+-------------------------------------+
CREATE TABLE gis_line (g LINESTRING);
INSERT INTO gis_line VALUES
(LineFromText('LINESTRING(0 0,0 10,10 0)')),
(LineStringFromText('LINESTRING(10 10,20 10,20 20,10 20,10
10)')),
(LineStringFromWKB(AsWKB(LineString(Point(10, 10),
Point(40, 10)))));
URL: https://mariadb.com/kb/en/linestring/https://mariadb.com/kb/en/linestring/ x �& % SOUNDS LIKESyntax
------
expr1 SOUNDS LIKE expr2
Description
-----------
This is the same as SOUNDEX(expr1) = SOUNDEX(expr2).
Example
SELECT givenname, surname FROM users WHERE givenname SOUNDS
LIKE "robert";
+-----------+---------+
| givenname | surname |
+-----------+---------+
| Roberto | Castro |
+-----------+---------+
URL: https://mariadb.com/kb/en/sounds-like/https://mariadb.com/kb/en/sounds-like/ y > % SPACESyntax
------
SPACE(N)
Description
-----------
Returns a string consisting of N space characters. If N is
NULL, returns NULL.
Examples
--------
SELECT QUOTE(SPACE(6));
+-----------------+
| QUOTE(SPACE(6)) |
+-----------------+
| ' ' |
+-----------------+
URL: https://mariadb.com/kb/en/space/https://mariadb.com/kb/en/space/ z �! % STRCMPSyntax
------
STRCMP(expr1,expr2)
Description
-----------
STRCMP() returns 0 if the strings are the same, -1 if the
first
argument is smaller than the second according to the current
sort order,
and 1 otherwise.
Examples
--------
SELECT STRCMP('text', 'text2');
+-------------------------+
| STRCMP('text', 'text2') |
+-------------------------+
| -1 |
+-------------------------+
SELECT STRCMP('text2', 'text');
+-------------------------+
| STRCMP('text2', 'text') |
+-------------------------+
| 1 |
+-------------------------+
SELECT STRCMP('text', 'text');
+------------------------+
| STRCMP('text', 'text') |
+------------------------+
| 0 |
+------------------------+
URL: https://mariadb.com/kb/en/strcmp/https://mariadb.com/kb/en/strcmp/ { x ! % SUBSTRDescription
-----------
SUBSTR() is a synonym for SUBSTRING().
URL: https://mariadb.com/kb/en/substr/https://mariadb.com/kb/en/substr/ � � % UCASESyntax
------
UCASE(str)
Description
-----------
UCASE() is a synonym for UPPER().
URL: https://mariadb.com/kb/en/ucase/https://mariadb.com/kb/en/ucase/ � � % UPPERSyntax
------
UPPER(str)
Description
-----------
Returns the string str with all characters changed to
uppercase
according to the current character set mapping. The default
is latin1
(cp1252 West European).
SELECT UPPER(surname), givenname FROM users ORDER BY
surname;
+----------------+------------+
| UPPER(surname) | givenname |
+----------------+------------+
| ABEL | Jacinto |
| CASTRO | Robert |
| COSTA | Phestos |
| MOSCHELLA | Hippolytos |
+----------------+------------+
UPPER() is ineffective when applied to binary strings
(BINARY,
VARBINARY, BLOB). The description of
LOWER() shows how to
perform lettercase conversion of binary strings.
URL: https://mariadb.com/kb/en/upper/https://mariadb.com/kb/en/upper/ a�� �� � fq��� ��0E � K l" POLYGONSyntax
------
Polygon(ls1,ls2,...)
Description
-----------
Constructs a WKB Polygon value from a number of WKB
LineString
arguments. If any argument does not represent the WKB of a
LinearRing (that is,
not a closed and simple LineString) the return value is
NULL.
Note that according to the OpenGIS standard, a POLYGON
should have exactly one ExteriorRing and all other rings
should lie within that ExteriorRing and thus be the
InteriorRings. Practically, however, some systems, including
MariaDB's, permit polygons to have several
'ExteriorRings'. In the case of there being multiple,
non-overlapping exterior rings ST_NUMINTERIORRINGS() will
return 1.
Examples
--------
SET @g = ST_GEOMFROMTEXT('POLYGON((1 1,1 5,4 9,6 9,9 3,7
2,1 1))');
CREATE TABLE gis_polygon (g POLYGON);
INSERT INTO gis_polygon VALUES
(PolygonFromText('POLYGON((10 10,20 10,20 20,10 20,10
10))')),
(PolyFromText('POLYGON((0 0,50 0,50 50,0 50,0 0), (10
10,20 10,20 20,10 20,10 10))')),
(PolyFromWKB(AsWKB(Polygon(LineString(Point(0, 0),
Point(30, 0), Point(30, 30), Point(0, 0))))));
Non-overlapping 'polygon':
SELECT ST_NumInteriorRings(ST_PolyFromText('POLYGON((0 0,10
0,10 10,0 10,0 0),
(-1 -1,-5 -1,-5 -5,-1 -5,-1 -1))')) AS NumInteriorRings;
+------------------+
| NumInteriorRings |
+------------------+
| 1 |
+------------------+
URL: https://mariadb.com/kb/en/polygon/https://mariadb.com/kb/en/polygon/ L �$ ST_BUFFERSyntax
------
ST_BUFFER(g1,r)
BUFFER(g1,r)
Description
-----------
Returns a geometry that represents all points whose distance
from geometry g1 is less than or equal to distance, or
radius, r.
Uses for this function could include creating for example a
new geometry representing a buffer zone around an island.
BUFFER() is a synonym.
Examples
--------
Determining whether a point is within a buffer zone:
SET @g1 = ST_GEOMFROMTEXT('POLYGON((10 10, 10 20, 20 20, 20
10, 10 10))');
SET @g2 = ST_GEOMFROMTEXT('POINT(8 8)');
SELECT ST_WITHIN(@g2,ST_BUFFER(@g1,5));
+---------------------------------+
| ST_WITHIN(@g2,ST_BUFFER(@g1,5)) |
+---------------------------------+
| 1 |
+---------------------------------+
SELECT ST_WITHIN(@g2,ST_BUFFER(@g1,1));
+---------------------------------+
| ST_WITHIN(@g2,ST_BUFFER(@g1,1)) |
+---------------------------------+
| 0 |
+---------------------------------+
URL: https://mariadb.com/kb/en/st_buffer/https://mariadb.com/kb/en/st_buffer/ M
'( ST_CONVEXHULLST_ConvexHull() was introduced in MariaDB 10.1.2
Syntax
------
ST_ConvexHull(g)
ConvexHull(g)
Description
-----------
Given a geometry, returns a geometry that is the minimum
convex geometry enclosing all geometries within the set.
Returns NULL if the geometry value is NULL or an empty
value.
ST_ConvexHull() and ConvexHull() are synonyms.
Examples
--------
The ConvexHull of a single point is simply the single point:
SET @g = ST_GEOMFROMTEXT('Point(0 0)');
SELECT ST_ASTEXT(ST_CONVEXHULL(@g));
+------------------------------+
| ST_ASTEXT(ST_CONVEXHULL(@g)) |
+------------------------------+
| POINT(0 0) |
+------------------------------+
SET @g = ST_GEOMFROMTEXT('MultiPoint(0 0, 1 2, 2 3)');
SELECT ST_ASTEXT(ST_CONVEXHULL(@g));
+------------------------------+
| ST_ASTEXT(ST_CONVEXHULL(@g)) |
+------------------------------+
| POLYGON((0 0,1 2,2 3,0 0)) |
+------------------------------+
SET @g = ST_GEOMFROMTEXT('MultiPoint( 1 1, 2 2, 5 3, 7 2, 9
3, 8 4, 6 6, 6 9, 4 9, 1 5 )');
SELECT ST_ASTEXT(ST_CONVEXHULL(@g));
+----------------------------------------+
| ST_ASTEXT(ST_CONVEXHULL(@g)) |
+----------------------------------------+
| POLYGON((1 1,1 5,4 9,6 9,9 3,7 2,1 1)) |
+----------------------------------------+
URL: https://mariadb.com/kb/en/st_convexhull/https://mariadb.com/kb/en/st_convexhull/ P �+ ST_SYMDIFFERENCESyntax
------
ST_SYMDIFFERENCE(g1,g2)
Description
-----------
Returns a geometry that represents the portions of geometry
g1 and geometry g2 that don't intersect.
Examples
--------
SET @g1 = ST_GEOMFROMTEXT('LINESTRING(10 20, 10 40)');
SET @g2 = ST_GEOMFROMTEXT('LINESTRING(10 15, 10 25)');
SELECT ASTEXT(ST_SYMDIFFERENCE(@g1,@g2));
+----------------------------------------------+
| ASTEXT(ST_SYMDIFFERENCE(@g1,@g2)) |
+----------------------------------------------+
| MULTILINESTRING((10 15,10 20),(10 25,10 40)) |
+----------------------------------------------+
SET @g2 = ST_GeomFromText('LINESTRING(10 20, 10 41)');
SELECT ASTEXT(ST_SYMDIFFERENCE(@g1,@g2));
+-----------------------------------+
| ASTEXT(ST_SYMDIFFERENCE(@g1,@g2)) |
+-----------------------------------+
| LINESTRING(10 40,10 41) |
+-----------------------------------+
URL: https://mariadb.com/kb/en/st_symdifference/https://mariadb.com/kb/en/st_symdifference/ Q \# ST_UNIONSyntax
------
ST_UNION(g1,g2)
Description
-----------
Returns a geometry that is the union of the geometry g1 and
geometry g2.
Examples
--------
SET @g1 = GEOMFROMTEXT('POINT (0 2)');
SET @g2 = GEOMFROMTEXT('POINT (2 0)');
SELECT ASTEXT(ST_UNION(@g1,@g2));
+---------------------------+
| ASTEXT(ST_UNION(@g1,@g2)) |
+---------------------------+
| MULTIPOINT(2 0,0 2) |
+---------------------------+
SET @g1 = GEOMFROMTEXT('POLYGON((0 0,0 3,3 3,3 0,0 0))');
SET @g2 = GEOMFROMTEXT('POLYGON((2 2,4 2,4 4,2 4,2 2))');
SELECT ASTEXT(ST_UNION(@g1,@g2));
+------------------------------------------------+
| ASTEXT(ST_UNION(@g1,@g2)) |
+------------------------------------------------+
| POLYGON((0 0,0 3,2 3,2 4,4 4,4 2,3 2,3 0,0 0)) |
+------------------------------------------------+
URL: https://mariadb.com/kb/en/st_union/https://mariadb.com/kb/en/st_union/ � c. ' ALTER LOGFILE GROUPSyntax
------
ALTER LOGFILE GROUP logfile_group
ADD UNDOFILE 'file_name'
[INITIAL_SIZE [=] size]
[WAIT]
ENGINE [=] engine_name
The ALTER LOGFILE GROUP statement is not supported by
MariaDB. It was originally inherited from MySQL NDB Cluster.
See MDEV-19295 for more information.
URL: https://mariadb.com/kb/en/alter-logfile-group/https://mariadb.com/kb/en/alter-logfile-group/ � �' ' ALTER SERVERSyntax
------
ALTER SERVER server_name
OPTIONS (option [, option] ...)
Description
-----------
Alters the server information for server_name, adjusting the
specified
options as per the CREATE SERVER command. The corresponding
fields in the mysql.servers table are updated accordingly.
This statement requires the SUPER privilege.
Examples
--------
ALTER SERVER s OPTIONS (USER 'sally');
URL: https://mariadb.com/kb/en/alter-server/https://mariadb.com/kb/en/alter-server/�� @� � �� Hl& ' ALTER TABLE � ]+ ' ALTER TABLESPACEThe ALTER TABLESPACE statement is not supported by MariaDB.
It was originally inherited from MySQL NDB Cluster. In MySQL
5.7 and later, the statement is also supported for InnoDB.
However, MariaDB has chosen not to include that specific
feature. See MDEV-19294 for more information.
URL: https://mariadb.com/kb/en/alter-tablespace/https://mariadb.com/kb/en/alter-tablespace/�� @� � �� S(* ' CREATE FUNCTION�� @ �� � + ' CREATE PROCEDURE�� @� � �� �' ' CREATE TABLE � 0 Y - & 3 ��Q/ U����(�� j� � �JY �\ R �' BACKUP STAGEBACKUP STAGE commands are a set of commands to make it
possible to make an efficient external backup tool.
The BACKUP STAGE command was introduced in MariaDB 10.4.1.
Syntax
------
BACKUP STAGE [START | FLUSH | BLOCK_DDL | BLOCK_COMMIT | END
]
In the following text, a transactional table means InnoDB or
"InnoDB-like engine with redo log that can lock redo purges
and can be copied without locks by an outside process".
In the text we refer to mariabackup as the backup tool to
use. However the description should work for any tools that
support BACKUP STAGEs.
Goals with BACKUP STAGE Commands
To be able to do a majority of the backup with the minimum
possible server locks. Especially for transactional tables
(InnoDB, MyRocks etc) there is only need for a very short
block of new commits while copying statistics and log
tables.
DDL are only needed to be blocked for a very short duration
of the backup while mariabackup is copying the tables
affected by DDL during the initial part of the backup.
Most non transactional tables (those that are not in use)
will be copied during BACKUP STAGE START. The exceptions are
system statistic and log tables that are not blocked during
the backup until BLOCK_COMMIT.
Should work efficiently with backup tools that use disk
snapshots.
Should work as efficiently as possible for all table types
that store data on the local disks.
As little copying as possible under higher level
stages/locks. For example, .frm (dictionary) and .trn
(trigger) files should be copying while copying the table
data.
BACKUP STAGE Commands
BACKUP STAGE START
Things Done by STAGE START
Blocks purge of redo files for storage engines that needs
this (Aria)
Start logging of DDL commands into 'datadir'/ddl.log. This
may take a short time as the command has to wait until there
all now active DDL commands.
mariabackup Under START
mariabackup can, under START:
Copy all transactional tables, aria_log_control, aria_log.#
and
other engines redo logs.
Call BACKUP STAGE FLUSH while copying the last set of files.
To copy InnoDB tables, mariabackup has to start to watch the
InnoDB backup redo log and copy all changes to the backup to
be able to run the redos later on in the final backup.
BACKUP STAGE FLUSH
Things Done by STAGE FLUSH
FLUSH all changes for inactive non-transactional tables,
except for statistics and log tables.
Close all tables that are not in use, to ensure they are
marked as closed for the backup.
BLOCK all new write locks for all non transactional tables
(except statistics and log tables). The command will not
wait for tables that are in use by read-only transactions.
DDLs don't have to be blocked at this stage as they can't
cause the table to be in an inconsistent state. This is true
also for non-transactional tables.
mariabackup under STAGE_FLUSH
mariabackup can, under STAGE FLUSH:
Copy all non-transactional tables that are not in use. This
list of used tables can be found with SHOW OPEN TABLES
Copy all new changes to the aria_log.# tables
At this point data for all old tables should have been
copied (except for some system tables).
BACKUP STAGE BLOCK_DDL
Things Done by BLOCK_DDL
Wait for all statements using write locked non-transactional
tables to end.
Blocks CREATE TABLE, DROP TABLE, TRUNCATE TABLE, and RENAME
TABLE.
Blocks also start off a new ALTER TABLE and the final rename
phase of ALTER TABLE. Running ALTER TABLES are not blocked.
mariabackup under BLOCK_DDL
mariabackup can, under BLOCK_DDL:
Copy the non-transactional tables that were in use during
STAGE FLUSH
Copy new tables created before BLOCK DDL. The file names can
be read from ddl.log. The log also allows the backup to
execute renames of files for which RENAME TABLE was done
instead of copying them.
Add markers to backup stream of tables that were dropped
during the earlier BACKUP STAGEs.
Copy changes to system log tables (this is easy as these are
append only)
Copy changes to aria_log.# tables (this is easy as these are
append only)
BACKUP STAGE BLOCK_COMMIT
Things Done by BLOCK_COMMIT
Lock the binary log and commit/rollback to ensure that no
changes are committed to any tables. If there are active
commits or data to be copied to the binary log this will be
allowed to finish.
This doesn't lock temporary tables that are not used by
replication. However these will be blocked when it's time
to write to the binary log.
Lock system log tables and statistics tables, flush them and
mark them closed.
When the BLOCK_COMMIT's stages return, this is the 'backup
time'. Everything committed will be in the backup and
everything not committed will roll back.
Transactional engines will continue to do changes to the
redo log during the BLOCK COMMIT stage, but this is not
important as all of these will roll back later as the
changes will not be committed.
mariabackup Under BLOCK_COMMIT
mariabackup can, under BLOCK_COMMIT:
Copy the last changes to the redo files for InnoDB and Aria
(aria_log.#), and the part of the binary log that was not
copied before.
MyRocks files can also be hard linked to the backup
directory
End of system log tables (slow_log and general_log) and all
statistics tables (table_stats, column_stats and
index_stats) should also be copied.
BACKUP STAGE END
Things Done by END
End DDL logging
Free resources
mariabackup After END
mariabackup can, after END:
Copy MyRocks tables
Using BACKUP STAGE With Disk Snapshots
A tool that is using disk snapshots for copying MariaDB
files should do
BACKUP STAGE START
BACKUP STAGE BLOCK_COMMIT
disk snapshot
BACKUP STAGE END
The above ensures that all non-transactional tables are
properly flushed to disk before the snapshot is done.
Using BACKUP STAGEs is also more efficient than using FLUSH
TABLES WITH READ LOCK as the above set of commands will not
block or be blocked by write operations to transactional
tables.
Note that when the backup is completed, one should delete
all files with the "#sql" prefix, as these are files used
by concurrent running ALTER TABLE. Note that InnoDB will on
server restart automatically delete any tables with the
"#sql" prefix.
Privileges
BACKUP STAGE requires the RELOAD privilege.
Other Things
Only one connection can run BACKUP STAGE START. If a second
connection tries, it will wait until the first one has
executed BACKUP STAGE END.
If the user skips a BACKUP STAGE, all intermediate backup
stages will automatically be run. This will allow us to add
new BACKUP STAGEs in the future with even more precise locks
without causing problems for tools using an earlier version
of BACKUP STAGEs
While opening files for a table, mariabackup should use
BACKUP LOCK to ensure that all files for a table are from
the same generation, that is, created at the same time.
One can use the max_statement_time or lock_wait_timeout
variables to ensure that a BACKUP STAGE command doesn't
block the server too long.
DDL logging will only be available in MariaDB Enterprise
server 10.2, 10.3 and 10.4.
URL: https://mariadb.com/kb/en/backup-stage/https://mariadb.com/kb/en/backup-stage/ � _, ' CREATE TABLESPACEThe CREATE TABLESPACE statement is not supported by MariaDB.
It was originally inherited from MySQL NDB Cluster. In MySQL
5.7 and later, the statement is also supported for InnoDB.
However, MariaDB has chosen not to include that specific
feature. See MDEV-19294 for more information.
URL: https://mariadb.com/kb/en/create-tablespace/https://mariadb.com/kb/en/create-tablespace/ �� �<]r�
�� S e& BACKUP LOCKThe BACKUP LOCK command was introduced in MariaDB 10.4.2.
BACKUP LOCK blocks a table from DDL statements. This is
mainly intended to be used by tools like mariabackup that
need to ensure there are no DDLs on a table while the table
files are opened. For example, for an Aria table that stores
data in 3 files with extensions .frm, .MAI and .MAD.
Normal read/write operations can continue as normal.
Syntax
------
To lock a table:
BACKUP LOCK table_name
To unlock a table:
BACKUP UNLOCK
Usage in a Backup Tool
BACKUP LOCK [database.]table_name;
- Open all files related to a table (for example, t.frm,
t.MAI and t.MYD)
BACKUP UNLOCK;
- Copy data
- Close files
This ensures that all files are from the same generation,
that is created at the same time by the MariaDB server.
Privileges
BACKUP LOCK requires the RELOAD privilege.
Notes
The idea is that the BACKUP LOCK should be held for as short
a time as possible by the backup tool. The time to take an
uncontested lock is very short! One can easily do 50,000
locks/unlocks per second on low end hardware.
One should use different connections for BACKUP STAGE
commands and BACKUP LOCK.
Implementation
Internally, BACKUP LOCK is implemented by taking an
MDLSHARED_HIGH_PRIO MDL lock on the table object, which
protects the table from any DDL operations.
URL: https://mariadb.com/kb/en/backup-lock/https://mariadb.com/kb/en/backup-lock/ U �& CACHE INDEXSyntax
------
CACHE INDEX
tbl_index_list [, tbl_index_list] ...
IN key_cache_name
tbl_index_list:
tbl_name [[INDEX|KEY] (index_name[, index_name] ...)]
Description
-----------
The CACHE INDEX statement assigns table indexes to a
specific key
cache. It is used only for MyISAM tables.
A default key cache exists and cannot be destroyed. To
create more key caches, the key_buffer_size server system
variable.
The associations between tables indexes and key caches are
lost on server restart. To recreate them automatically, it
is necessary to configure caches in a configuration file and
include some CACHE INDEX (and optionally LOAD INDEX)
statements in the init file.
Examples
--------
The following statement assigns indexes from the tables t1,
t2, and t3
to the key cache named hot_cache:
CACHE INDEX t1, t2, t3 IN hot_cache;
+---------+--------------------+----------+----------+
| Table | Op | Msg_type | Msg_text |
+---------+--------------------+----------+----------+
| test.t1 | assign_to_keycache | status | OK |
| test.t2 | assign_to_keycache | status | OK |
| test.t3 | assign_to_keycache | status | OK |
+---------+--------------------+----------+----------+
Implementation (for MyISAM)
Normally CACHE INDEX should not take a long time to execute.
Internally it's implemented the following way:
Find the right key cache (under
LOCK_global_system_variables)
Open the table with a TL_READ_NO_INSERT lock.
Flush the original key cache for the given file (under key
cache lock)
Flush the new key cache for the given file (safety)
Move the file to the new key cache (under file share lock)
The only possible long operations are getting the locks for
the table and flushing the original key cache, if there were
many key blocks for the file in it.
We plan to also add CACHE INDEX for Aria tables if there is
a need for this.
URL: https://mariadb.com/kb/en/cache-index/https://mariadb.com/kb/en/cache-index/ X �2 FLUSH TABLES FOR EXPORTFLUSH TABLES ... FOR EXPORT was introduced in MariaDB
10.0.8.
Syntax
------
FLUSH TABLES table_name [, table_name] FOR EXPORT
Description
-----------
FLUSH TABLES ... FOR EXPORT flushes changes to the specified
tables to disk so that binary copies can be made while the
server is still running. This works for Archive, Aria, CSV,
InnoDB, MyISAM, MERGE, and XtraDB tables.
The table is read locked until one has issued UNLOCK TABLES.
If a storage engine does not support FLUSH TABLES FOR
EXPORT, a 1031 error (SQLSTATE 'HY000') is produced.
If FLUSH TABLES ... FOR EXPORT is in effect in the session,
the following statements will produce an error if attempted:
FLUSH TABLES WITH READ LOCK
FLUSH TABLES ... WITH READ LOCK
FLUSH TABLES ... FOR EXPORT
Any statement trying to update any table
If any of the following statements is in effect in the
session, attempting FLUSH TABLES ... FOR EXPORT will
produce an error.
FLUSH TABLES ... WITH READ LOCK
FLUSH TABLES ... FOR EXPORT
LOCK TABLES ... READ
LOCK TABLES ... WRITE
FLUSH FOR EXPORT is not written to the binary log.
This statement requires the RELOAD and the LOCK TABLES
privileges.
If one of the specified tables cannot be locked, none of the
tables will be locked.
If a table does not exist, an error like the following will
be produced:
ERROR 1146 (42S02): Table 'test.xxx' doesn't exist
If a table is a view, an error like the following will be
produced:
ERROR 1347 (HY000): 'test.v' is not BASE TABLE
Example
FLUSH TABLES test.t1 FOR EXPORT;
# Copy files related to the table (see below)
UNLOCK TABLES;
For a full description, please see copying MariaDB tables.
URL: https://mariadb.com/kb/en/flush-tables-for-export/https://mariadb.com/kb/en/flush-tables-for-export/�� @ �� 8& ' CREATE VIEW � ' ' DROP PACKAGEOracle-style packages were introduced in MariaDB 10.3.5.
Syntax
------
DROP PACKAGE [IF EXISTS] [ db_name . ] package_name
Description
-----------
The DROP PACKAGE statement can be used when Oracle SQL_MODE
is set.
The DROP PACKAGE statement drops a stored package entirely:
Drops the package specification (earlier created using the
CREATE PACKAGE statement).
Drops the package implementation, if the implementation was
already created using the CREATE PACKAGE BODY statement.
URL: https://mariadb.com/kb/en/drop-package/https://mariadb.com/kb/en/drop-package/ � u, ' DROP PACKAGE BODYOracle-style packages were introduced in MariaDB 10.3.5.
Syntax
------
DROP PACKAGE BODY [IF EXISTS] [ db_name . ] package_name
Description
-----------
The DROP PACKAGE BODY statement can be used when Oracle
SQL_MODE is set.
The DROP PACKAGE BODY statement drops the package body (i.e
the implementation), previously created using the CREATE
PACKAGE BODY statement.
Note, DROP PACKAGE BODY drops only the package
implementation, but does not drop the package specification.
Use DROP PACKAGE to drop the package entirely (i.e. both
implementation and specification).
URL: https://mariadb.com/kb/en/drop-package-body/https://mariadb.com/kb/en/drop-package-body/ � [* ' DROP TABLESPACEThe DROP TABLESPACE statement is not supported by MariaDB.
It was originally inherited from MySQL NDB Cluster. In MySQL
5.7 and later, the statement is also supported for InnoDB.
However, MariaDB has chosen not to include that specific
feature. See MDEV-19294 for more information.
URL: https://mariadb.com/kb/en/drop-tablespace/https://mariadb.com/kb/en/drop-tablespace/�� @ �e �� 1LA, ' Generated (Virtual and Persistent/Stored) Columns � t " ( LASTVALLASTVAL is a synonym for PREVIOUS VALUE for sequence_name.
URL: https://mariadb.com/kb/en/lastval/https://mariadb.com/kb/en/lastval/ � p " ( NEXTVALNEXTVAL is a synonym for NEXT VALUE for sequence_name.
URL: https://mariadb.com/kb/en/nextval/https://mariadb.com/kb/en/nextval/ Z � �� ZU �����Wy( o
�� �� \ Syntax
------
FLUSH [NO_WRITE_TO_BINLOG | LOCAL]
flush_option [, flush_option] ...
or when flushing tables:
FLUSH [NO_WRITE_TO_BINLOG | LOCAL] TABLES [table_list]
[table_flush_option]
where table_list is a list of tables separated by , (comma).
Description
-----------
The FLUSH statement clears or reloads various internal
caches used by
MariaDB. To execute FLUSH, you must have the RELOAD
privilege. See GRANT.
The RESET statement is similar to FLUSH. See
RESET.
You cannot issue a FLUSH statement from within a stored
function or a trigger. Doing so within a stored procedure is
permitted, as long as it is not called by a stored function
or trigger. See Stored Routine Limitations, Stored Function
Limitations and Trigger Limitations.
If a listed table is a view, an error like the following
will be produced:
ERROR 1347 (HY000): 'test.v' is not BASE TABLE
By default, FLUSH statements are written to the binary log
and will be replicated. The NO_WRITE_TO_BINLOG keyword
(LOCAL is an alias) will ensure the statement is not written
to the binary log.
The different flush options are:
Option | Description |
CHANGED_PAGE_BITMAPS | Internal command used for backup
purposes. See the Information Schema CHANGED_PAGE_BITMAPS
Table. |
CLIENT_STATISTICS | Reset client statistics (see SHOW
CLIENT_STATISTICS). |
DES_KEY_FILE | Reloads the DES key file (Specified with the
--des-key-file startup option). |
HOSTS | Flush the hostname cache (used for converting ip to
host names and for unblocking blocked hosts. See
max_connect_errors) |
INDEX_STATISTICS | Reset index statistics (see SHOW
INDEX_STATISTICS). |
[ERROR | ENGINE | GENERAL | SLOW | BINARY | RELAY] LOGS |
Close and reopen the specified log type, or all log types if
none are specified. FLUSH RELAY LOGS [connection-name] can
be used to flush the relay logs for a specific connection.
Only one connection can be specified per FLUSH command. See
Multi-source replication. FLUSH ENGINE LOGS will delete all
unneeded Aria redo logs. Since MariaDB 10.1.30 and MariaDB
10.2.11, FLUSH BINARY LOGS
DELETE_DOMAIN_ID=(list-of-domains) can be used to discard
obsolete GTID domains from the server's binary log state.
In order for this to be successful, no event group from the
listed GTID domains can be present in existing binary log
files. If some still exist, then they must be purged prior
to executing this command. If the command completes
successfully, then it also rotates the binary log. |
MASTER | Deprecated option, use RESET MASTER instead. |
PRIVILEGES | Reload all privileges from the privilege tables
in the mysql database. If the server is started with
--skip-grant-table option, this will activate the privilege
tables again. |
QUERY CACHE | Defragment the query cache to better utilize
its memory. If you want to reset the query cache, you can do
it with RESET QUERY CACHE. |
QUERY_RESPONSE_TIME | See the QUERY_RESPONSE_TIME plugin. |
SLAVE | Deprecated option, use RESET SLAVE instead. |
SSL | Used to dynamically reinitialize the server's TLS
context by reloading the files defined by several TLS system
variables. See FLUSH SSL for more information. This command
was first added in MariaDB 10.4.1. |
STATUS | Resets all server status variables that can be
reset to 0. Not all global status variables support this, so
not all global values are reset. See FLUSH STATUS for more
information. |
TABLE | Close tables given as options or all open tables if
no table list was used. From MariaDB 10.4.1, using without
any table list will only close tables not in use, and tables
not locked by the FLUSH TABLES connection. If there are no
locked tables, FLUSH TABLES will be instant and will not
cause any waits, as it no longer waits for tables in use.
When a table list is provided, from MariaDB 10.4.1, the
server will wait for the end of any transactions that are
using the tables. Previously, FLUSH TABLES only waited for
the statements to complete. |
TABLES | Same as FLUSH TABLE. |
TABLES ... FOR EXPORT | For InnoDB tables, flushes table
changes to disk to permit binary table copies while the
server is running. Introduced in MariaDB 10.0.8. See FLUSH
TABLES ... FOR EXPORT for more. |
TABLES WITH READ LOCK | Closes all open tables. New tables
are only allowed to be opened with read locks until an
UNLOCK TABLES is given. |
TABLES WITH READ LOCK AND DISABLE CHECKPOINT | As TABLES
WITH READ LOCK but also disable all checkpoint writes by
transactional table engines. This is useful when doing a
disk snapshot of all tables. |
TABLE_STATISTICS | Reset table statistics (see SHOW
TABLE_STATISTICS). |
USER_RESOURCES | Resets all per hour user resources. This
enables clients that have exhausted their resources to
connect again. |
USER_STATISTICS | Reset user statistics (see SHOW
USER_STATISTICS). |
You can also use the mysqladmin client to flush things. Use
mysqladmin --help to examine what flush commands it
supports.
FLUSH STATUS
Server status variables can be reset by executing the
following:
FLUSH STATUS;
Global Status Variables that Support FLUSH STATUS
Not all global status variables support being reset by FLUSH
STATUS. Currently, the following status variables are reset
by FLUSH STATUS:
Aborted_clients
Aborted_connects
Aria_pagecache_blocks_not_flushed
Aria_pagecache_blocks_unused
Aria_pagecache_blocks_used
Binlog_cache_disk_use
Binlog_cache_use
Binlog_stmt_cache_disk_use
Binlog_stmt_cache_use
Connection_errors_accept
Connection_errors_internal
Connection_errors_max_connections
Connection_errors_peer_address
Connection_errors_select
Connection_errors_tcpwrap
Created_tmp_files
Delayed_errors
Delayed_writes
Feature_check_constraint
Feature_delay_key_write
Max_used_connections
Opened_plugin_libraries
Performance_schema_accounts_lost
Performance_schema_cond_instances_lost
Performance_schema_digest_lost
Performance_schema_file_handles_lost
Performance_schema_file_instances_lost
Performance_schema_hosts_lost
Performance_schema_locker_lost
Performance_schema_mutex_instances_lost
Performance_schema_rwlock_instances_lost
Performance_schema_session_connect_attrs_lost
Performance_schema_socket_instances_lost
Performance_schema_stage_classes_lost
Performance_schema_statement_classes_lost
Performance_schema_table_handles_lost
Performance_schema_table_instances_lost
Performance_schema_thread_instances_lost
Performance_schema_users_lost
Qcache_hits
Qcache_inserts
Qcache_lowmem_prunes
Qcache_not_cached
Rpl_semi_sync_master_no_times
Rpl_semi_sync_master_no_tx
Rpl_semi_sync_master_timefunc_failures
Rpl_semi_sync_master_wait_pos_backtraverse
Rpl_semi_sync_master_yes_tx
Rpl_transactions_multi_engine
Server_audit_writes_failed
Slave_retried_transactions
Slow_launch_threads
Ssl_accept_renegotiates
Ssl_accepts
Ssl_callback_cache_hits
Ssl_client_connects
Ssl_connect_renegotiates
Ssl_ctx_verify_depth
Ssl_ctx_verify_mode
Ssl_finished_accepts
Ssl_finished_connects
Ssl_session_cache_hits
Ssl_session_cache_misses
Ssl_session_cache_overflows
Ssl_session_cache_size
Ssl_session_cache_timeouts
Ssl_sessions_reused
Ssl_used_session_cache_entries
Subquery_cache_hit
Subquery_cache_miss
Table_locks_immediate
Table_locks_waited
Tc_log_max_pages_used
Tc_log_page_waits
Transactions_gtid_foreign_engine
Transactions_multi_engine
FLUSH SSL
The FLUSH SSL command was first added in MariaDB 10.4.
In MariaDB 10.4 and later, the FLUSH SSL command can be used
to dynamically reinitialize the server's TLS context. This
is most useful if you need to replace a certificate that is
about to expire without restarting the server.
This operation is performed by reloading the files defined
by the following TLS system variables:
ssl_cert
ssl_key
ssl_ca
ssl_capath
ssl_crl
ssl_crlpath
These TLS system variables are not dynamic, so their values
can not be changed without restarting the server.
If you want to dynamically reinitialize the server's TLS
context, then you need to change the certificate and key
files at the relevant paths defined by these TLS system
variables, without actually changing the values of the
variables. See MDEV-19341 for more information.
Reducing Memory Usage 8A� �$ Y �' HELP CommandSyntax
------
HELP search_string
Description
-----------
The HELP command can be used in any MariaDB client, such as
the mysql command-line client, to get basic syntax help and
a short description for most commands and functions.
If you provide an argument to the HELP command, the mysql
client uses it as a search string to access server-side
help. The proper operation of this command requires that the
help tables in the mysql database be initialized with help
topic information.
If there is no match for the search string, the search
fails. Use help contents to see a list of the help
categories:
HELP contents
You asked for help about help category: "Contents"
For more information, type 'help ', where is one of the
following
categories:
Account Management
Administration
Compound Statements
Data Definition
Data Manipulation
Data Types
Functions
Functions and Modifiers for Use with GROUP BY
Geographic Features
Help Metadata
Language Structure
Plugins
Procedures
Sequences
Table Maintenance
Transactions
User-Defined Functions
Utility
If a search string matches multiple items, MariaDB shows a
list of matching topics:
HELP drop
Many help items for your request exist.
To make a more specific request, please type 'help ',
where is one of the following
topics:
ALTER TABLE
DROP DATABASE
DROP EVENT
DROP FUNCTION
DROP FUNCTION UDF
DROP INDEX
DROP PACKAGE
DROP PACKAGE BODY
DROP PROCEDURE
DROP ROLE
DROP SEQUENCE
DROP SERVER
DROP TABLE
DROP TRIGGER
DROP USER
DROP VIEW
Then you can enter a topic as the search string to see the
help entry for that topic.
The help is provided with the MariaDB server and makes use
of four help tables found in the mysql database:
help_relation, help_topic, help_category and help_keyword.
These tables are populated by the mysql_install_db or
fill_help_table.sql scripts which, until MariaDB 10.4.7,
contain data generated from an old version of MySQL.
URL: https://mariadb.com/kb/en/help-command/https://mariadb.com/kb/en/help-command/ Z X
B KILL [CONNECTION | QUERY]Syntax
------
KILL [HARD | SOFT] [CONNECTION | QUERY [ID] ] [thread_id |
USER user_name | query_id]
MariaDB 5.3.2
The options HARD | SOFT and USER username were introduced in
MariaDB 5.3.2
MariaDB 10.0.5
KILL QUERY ID query_id, which permits killing a query by
query id rather than thread id, was introduced in MariaDB
10.0.5.
Description
-----------
Each connection to mysqld runs in a separate thread. You can
see which threads
are running with the SHOW PROCESSLIST statement and kill a
thread with the KILL thread_id statement.
KILL allows the optional CONNECTION or
QUERY modifier:
KILL CONNECTION is the same as KILL with no
modifier: It terminates the connection associated with the
given thread or query id.
KILL QUERY terminates the statement that the connection
thread_id is
currently executing, but leaves the connection itself
intact.
KILL QUERY ID (introduced in MariaDB 10.0.5) terminates the
query by query_id, leaving the connection intact.
If a connection is terminated that has an active
transaction, the transaction will be rolled back. If only a
query is killed, the current transaction will stay active.
See also idle_transaction_timeout.
If you have the PROCESS privilege, you can see all threads.
If
you have the SUPER privilege, you can kill all threads and
statements. Otherwise, you can see and kill only your own
threads and
statements.
Killing queries that repair or create indexes on MyISAM and
Aria tables may result in corrupted tables. Use the SOFT
option to avoid this!
The HARD option (default) kills a command as soon as
possible. If you use
SOFT, then critical operations that may leave a table in an
inconsistent state will not be interrupted. Such operations
include REPAIR and INDEX creation for MyISAM and Aria tables
(REPAIR TABLE, OPTIMIZE TABLE).
KILL ... USER username will kill all connections/queries for
a
given user. USER can be specified one of the following ways:
username (Kill without regard to hostname)
username@hostname
CURRENT_USER or CURRENT_USER()
If you specify a thread id and that thread does not exist,
you get the following error:
ERROR 1094 (HY000): Unknown thread id:
If you specify a query id that doesn't exist, you get the
following error:
ERROR 1957 (HY000): Unknown query id:
However, if you specify a user name, no error is issued for
non-connected (or even non-existing) users. To check if the
connection/query has been killed, you can use the
ROW_COUNT() function.
A client whose connection is killed receives the following
error:
ERROR 1317 (70100): Query execution was interrupted
To obtain a list of existing sessions, use the SHOW
PROCESSLIST statement or query the Information Schema
PROCESSLIST table.
Note: You cannot use KILL with the Embedded MySQL Server
library because the embedded server merely runs inside the
threads of the host
application. It does not create any connection threads of
its own.
Note: You can also use
mysqladmin kill thread_id [,thread_id...]
to kill connections. To get a list of running queries,
use mysqladmin processlist. See mysqladmin.
Percona Toolkit contains a program, pt-kill that can be used
to automatically kill connections that match certain
criteria. For example, it can be used to terminate idle
connections, or connections that have been busy for more
than 60 seconds.
URL:
https://mariadb.com/kb/en/data-manipulation-kill-connection-query/https://mariadb.com/kb/en/data-manipulation-kill-connection-query/ �
G% ) JSON_ARRAYJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_ARRAY([value[, value2] ...])
Description
-----------
Returns a JSON array containing the listed values. The list
can be empty.
Example
SELECT Json_Array(56, 3.1416, 'My name is "Foo"', NULL);
+--------------------------------------------------+
| Json_Array(56, 3.1416, 'My name is "Foo"', NULL) |
+--------------------------------------------------+
| [56, 3.1416, "My name is \"Foo\"", null] |
+--------------------------------------------------+
URL: https://mariadb.com/kb/en/json_array/https://mariadb.com/kb/en/json_array/ � ' ) JSON_COMPACTThis function was added in MariaDB 10.2.4.
Syntax
------
JSON_COMPACT(json_doc)
Description
-----------
Removes all unnecessary spaces so the json document is as
short as possible.
Example
SET @j = '{ "A": 1, "B": [2, 3]}';
SELECT JSON_COMPACT(@j), @j;
+-------------------+------------------------+
| JSON_COMPACT(@j) | @j |
+-------------------+------------------------+
| {"A":1,"B":[2,3]} | { "A": 1, "B": [2, 3]} |
+-------------------+------------------------+
URL: https://mariadb.com/kb/en/json_compact/https://mariadb.com/kb/en/json_compact/ �
�( ) JSON_DETAILEDThis function was added in MariaDB 10.2.4.
Syntax
------
JSON_DETAILED(json_doc[, tab_size])
Description
-----------
Represents JSON in the most understandable way emphasizing
nested structures.
Example
SET @j = '{ "A":1,"B":[2,3]}';
SELECT @j;
+--------------------+
| @j |
+--------------------+
| { "A":1,"B":[2,3]} |
+--------------------+
SELECT JSON_DETAILED(@j);
+------------------------------------------------------------+
| JSON_DETAILED(@j) |
+------------------------------------------------------------+
| {
"A": 1,
"B":
[
2,
3
]
} |
+------------------------------------------------------------+
URL: https://mariadb.com/kb/en/json_detailed/https://mariadb.com/kb/en/json_detailed/ ��l^��&�
���& �� \ � RESETSyntax
------
RESET reset_option [, reset_option] ...
Description
-----------
The RESET statement is used to clear the state of various
server
operations. You must have the RELOAD privilege to execute
RESET.
RESET acts as a stronger version of the FLUSH statement.
The different RESET options are:
Option | Description |
SLAVE ["connection_name"] [ALL] | Deletes all relay logs
from the slave and reset the replication position in the
master binary log. |
MASTER | Deletes all old binary logs, makes the binary index
file (--log-bin-index) empty and creates a new binary log
file. This is useful when you want to reset the master to an
initial state. If you want to just delete old, not used
binary logs, you should use the PURGE BINARY LOGS command. |
QUERY CACHE | Removes all queries from the query cache. See
also FLUSH QUERY CACHE. |
URL: https://mariadb.com/kb/en/reset/https://mariadb.com/kb/en/reset/ ] � SETSyntax
------
SET variable_assignment [, variable_assignment] ...
variable_assignment:
user_var_name = expr
| [GLOBAL | SESSION] system_var_name = expr
| [@@global. | @@session. | @@]system_var_name = expr
One can also set a user variable in any expression with this
syntax:
user_var_name:= expr
Description
-----------
The SET statement assigns values to different types of
variables that affect the operation of the server or your
client. Older
versions of MySQL employed SET OPTION, but this syntax was
deprecated in favor of SET without OPTION, and was removed
in MariaDB 10.0.
Changing a system variable by using the SET statement does
not make the change permanently. To do so, the change must
be made in a configuration file.
For setting variables on a per-query basis (from MariaDB
10.1.2), see SET STATEMENT.
See SHOW VARIABLES for documentation on viewing server
system variables.
See Server System Variables for a list of all the system
variables.
GLOBAL / SESSION
When setting a system variable, the scope can be specified
as either GLOBAL or SESSION.
A global variable change affects all new sessions. It does
not affect any currently open sessions, including the one
that made the change.
A session variable change affects the current session only.
If the variable has a session value, not specifying either
GLOBAL or SESSION will be the same as specifying SESSION. If
the variable only has a global value, not specifying GLOBAL
or SESSION will apply to the change to the global value.
DEFAULT
Setting a global variable to DEFAULT will restore it to the
server default, and setting a session variable to DEFAULT
will restore it to the current global value.
Examples
--------
innodb_sync_spin_loops is a global variable.
skip_parallel_replication is a session variable.
max_error_count is both global and session.
SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM
INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE
VARIABLE_NAME LIKE 'max_error_count' OR
VARIABLE_NAME LIKE 'skip_parallel_replication' OR
VARIABLE_NAME LIKE 'innodb_sync_spin_loops';
+---------------------------+---------------+--------------+
| VARIABLE_NAME | SESSION_VALUE | GLOBAL_VALUE |
+---------------------------+---------------+--------------+
| MAX_ERROR_COUNT | 64 | 64 |
| SKIP_PARALLEL_REPLICATION | OFF | NULL |
| INNODB_SYNC_SPIN_LOOPS | NULL | 30 |
+---------------------------+---------------+--------------+
Setting the session values:
SET max_error_count=128;
Query OK, 0 rows affected (0.000 sec)
SET skip_parallel_replication=ON;
Query OK, 0 rows affected (0.000 sec)
SET innodb_sync_spin_loops=60;
ERROR 1229 (HY000): Variable 'innodb_sync_spin_loops' is a
GLOBAL variable
and should be set with SET GLOBAL
SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM
INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE
VARIABLE_NAME LIKE 'max_error_count' OR
VARIABLE_NAME LIKE 'skip_parallel_replication' OR
VARIABLE_NAME LIKE 'innodb_sync_spin_loops';
+---------------------------+---------------+--------------+
| VARIABLE_NAME | SESSION_VALUE | GLOBAL_VALUE |
+---------------------------+---------------+--------------+
| MAX_ERROR_COUNT | 128 | 64 |
| SKIP_PARALLEL_REPLICATION | ON | NULL |
| INNODB_SYNC_SPIN_LOOPS | NULL | 30 |
+---------------------------+---------------+--------------+
Setting the global values:
SET GLOBAL max_error_count=256;
SET GLOBAL skip_parallel_replication=ON;
ERROR 1228 (HY000): Variable 'skip_parallel_replication'
is a SESSION variable
and can't be used with SET GLOBAL
SET GLOBAL innodb_sync_spin_loops=120;
SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM
INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE
VARIABLE_NAME LIKE 'max_error_count' OR
VARIABLE_NAME LIKE 'skip_parallel_replication' OR
VARIABLE_NAME LIKE 'innodb_sync_spin_loops';
+---------------------------+---------------+--------------+
| VARIABLE_NAME | SESSION_VALUE | GLOBAL_VALUE |
+---------------------------+---------------+--------------+
| MAX_ERROR_COUNT | 128 | 256 |
| SKIP_PARALLEL_REPLICATION | ON | NULL |
| INNODB_SYNC_SPIN_LOOPS | NULL | 120 |
+---------------------------+---------------+--------------+
SHOW VARIABLES will by default return the session value
unless the variable is global only.
SHOW VARIABLES LIKE 'max_error_count';
+-----------------+-------+
| Variable_name | Value |
+-----------------+-------+
| max_error_count | 128 |
+-----------------+-------+
SHOW VARIABLES LIKE 'skip_parallel_replication';
+---------------------------+-------+
| Variable_name | Value |
+---------------------------+-------+
| skip_parallel_replication | ON |
+---------------------------+-------+
SHOW VARIABLES LIKE 'innodb_sync_spin_loops';
+------------------------+-------+
| Variable_name | Value |
+------------------------+-------+
| innodb_sync_spin_loops | 120 |
+------------------------+-------+
Using the inplace syntax:
SELECT (@a:=1);
+---------+
| (@a:=1) |
+---------+
| 1 |
+---------+
SELECT @a;
+------+
| @a |
+------+
| 1 |
+------+
URL: https://mariadb.com/kb/en/set/https://mariadb.com/kb/en/set/ �
% ) JSON_LOOSEThis function was added in MariaDB 10.2.4.
Syntax
------
JSON_LOOSE(json_doc)
Description
-----------
Adds spaces to a JSON document to make it look more
readable.
Example
SET @j = '{ "A":1,"B":[2,3]}';
SELECT JSON_LOOSE(@j), @j;
+-----------------------+--------------------+
| JSON_LOOSE(@j) | @j |
+-----------------------+--------------------+
| {"A": 1, "B": [2, 3]} | { "A":1,"B":[2,3]} |
+-----------------------+--------------------+
URL: https://mariadb.com/kb/en/json_loose/https://mariadb.com/kb/en/json_loose/ � x& ) JSON_OBJECTJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_OBJECT([key, value[, key, value] ...])
Description
-----------
Returns a JSON object containing the given key/value pairs.
The key/value list can be empty.
An error will occur if there are an odd number of arguments,
or any key name is NULL.
Example
SELECT JSON_OBJECT("id", 1, "name", "Monty");
+---------------------------------------+
| JSON_OBJECT("id", 1, "name", "Monty") |
+---------------------------------------+
| {"id": 1, "name": "Monty"} |
+---------------------------------------+
URL: https://mariadb.com/kb/en/json_object/https://mariadb.com/kb/en/json_object/ >��?�, �>W� �� ^
,% About SHOWSHOW has many forms that provide information about
databases, tables, columns, or status information about the
server. These include:
SHOW AUTHORS
SHOW CHARACTER SET [like_or_where]
SHOW COLLATION [like_or_where]
SHOW [FULL] COLUMNS FROM tbl_name [FROM db_name]
[like_or_where]
SHOW CONTRIBUTORS
SHOW CREATE DATABASE db_name
SHOW CREATE EVENT event_name
SHOW CREATE PACKAGE package_name
SHOW CREATE PACKAGE BODY package_name
SHOW CREATE PROCEDURE proc_name
SHOW CREATE TABLE tbl_name
SHOW CREATE TRIGGER trigger_name
SHOW CREATE VIEW view_name
SHOW DATABASES [like_or_where]
SHOW ENGINE engine_name {STATUS | MUTEX}
SHOW [STORAGE] ENGINES
SHOW ERRORS [LIMIT [offset,] row_count]
SHOW [FULL] EVENTS
SHOW FUNCTION CODE func_name
SHOW FUNCTION STATUS [like_or_where]
SHOW GRANTS FOR user
SHOW INDEX FROM tbl_name [FROM db_name]
SHOW INNODB STATUS
SHOW OPEN TABLES [FROM db_name] [like_or_where]
SHOW PLUGINS
SHOW PROCEDURE CODE proc_name
SHOW PROCEDURE STATUS [like_or_where]
SHOW PRIVILEGES
SHOW [FULL] PROCESSLIST
SHOW PROFILE [types] [FOR QUERY n] [OFFSET n] [LIMIT n]
SHOW PROFILES
SHOW [GLOBAL | SESSION] STATUS [like_or_where]
SHOW TABLE STATUS [FROM db_name] [like_or_where]
SHOW TABLES [FROM db_name] [like_or_where]
SHOW TRIGGERS [FROM db_name] [like_or_where]
SHOW [GLOBAL | SESSION] VARIABLES [like_or_where]
SHOW WARNINGS [LIMIT [offset,] row_count]
like_or_where:
LIKE 'pattern'
| WHERE expr
If the syntax for a given SHOW statement includes a
LIKE 'pattern' part, 'pattern' is a
string that can contain the SQL "%" and
"_" wildcard characters. The pattern is useful for
restricting statement output to matching values.
Several SHOW statements also accept a
WHERE clause that provides more flexibility in specifying
which rows to display. See Extended Show.
URL: https://mariadb.com/kb/en/about-show/https://mariadb.com/kb/en/about-show/ _ ' SHOW AUTHORSSyntax
------
SHOW AUTHORS
Description
-----------
The SHOW AUTHORS statement displays information about the
people who work on MariaDB. For each author, it displays
Name, Location, and
Comment values. All columns are encoded as latin1.
In MariaDB 5.5 this is in somewhat random order.
In MariaDB 10.0.5 and later you have:
First the active people in MariaDB are listed.
Then the active people in MySQL.
Last the people that has contributed to MariaDB/MySQL in the
past.
The order is somewhat related to importance of the
contribution given to the MariaDB project, but this is not
100% accurate. There is still room for improvements and
debate...
Example
SHOW AUTHORS;
+--------------------------------+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------+
| Name | Location | Comment |
+--------------------------------+---------------------------------------+-----------------------------------------------------------------------------------------------------------------------------------------+
| Michael (Monty) Widenius | Tusby, Finland | Lead developer
and main author |
| Sergei Golubchik | Kerpen, Germany | Architect, Full-text
search, precision math, plugin framework, merges etc |
| Igor Babaev | Bellevue, USA | Optimizer, keycache, core
work |
| Sergey Petrunia | St. Petersburg, Russia | Optimizer |
| Oleksandr Byelkin | Lugansk, Ukraine | Query Cache (4.0),
Subqueries (4.1), Views (5.0) |
| Timour Katchaounov | Sofia , Bulgaria | Optimizer |
| Kristian Nielsen | Copenhagen, Denmark | Replication,
Async client prototocol, General buildbot stuff |
| Alexander (Bar) Barkov | Izhevsk, Russia | Unicode and
character sets |
| Alexey Botchkov (Holyfoot) | Izhevsk, Russia | GIS
extensions, embedded server, precision math |
| Daniel Bartholomew | Raleigh, USA | MariaDB documentation
|
| Colin Charles | Selangor, Malesia | MariaDB documentation,
talks at a LOT of conferences |
| Sergey Vojtovich | Izhevsk, Russia | initial
implementation of plugin architecture, maintained native
storage engines (MyISAM, MEMORY, ARCHIVE, etc), rewrite of
table cache |
| Vladislav Vaintroub | Mannheim, Germany | MariaDB Java
connector, new thread pool, Windows optimizations |
| Elena Stepanova | Sankt Petersburg, Russia | QA, test
cases |
| Georg Richter | Heidelberg, Germany | New LGPL C
connector, PHP connector |
| Jan Lindström | Ylämylly, Finland | Working on InnoDB |
| Lixun Peng | Hangzhou, China | Multi Source replication |
| Percona | CA, USA | XtraDB, microslow patches, extensions
to slow log
...
See Also
SHOW CONTRIBUTORS. This list all members and sponsors of the
MariaDB Foundation and other sponsors.
URL: https://mariadb.com/kb/en/show-authors/https://mariadb.com/kb/en/show-authors/ ` �+ SHOW BINARY LOGSSyntax
------
SHOW BINARY LOGS
SHOW MASTER LOGS
Description
-----------
Lists the binary log files on the server. This statement is
used as part of the
procedure described in
PURGE BINARY LOGS, that shows how to
determine which logs can be purged.
Examples
--------
SHOW BINARY LOGS;
+--------------------+-----------+
| Log_name | File_size |
+--------------------+-----------+
| mariadb-bin.000001 | 19039 |
| mariadb-bin.000002 | 717389 |
| mariadb-bin.000003 | 300 |
| mariadb-bin.000004 | 333 |
| mariadb-bin.000005 | 899 |
| mariadb-bin.000006 | 125 |
| mariadb-bin.000007 | 18907 |
| mariadb-bin.000008 | 19530 |
| mariadb-bin.000009 | 151 |
| mariadb-bin.000010 | 151 |
| mariadb-bin.000011 | 125 |
| mariadb-bin.000012 | 151 |
| mariadb-bin.000013 | 151 |
| mariadb-bin.000014 | 125 |
| mariadb-bin.000015 | 151 |
| mariadb-bin.000016 | 314 |
+--------------------+-----------+
URL: https://mariadb.com/kb/en/show-binary-logs/https://mariadb.com/kb/en/show-binary-logs/ � O# ) JSON_SETJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_SET(json_doc, path, val[, path, val] ...)
Description
-----------
Updates or inserts data into a JSON document, returning the
result, or NULL if any of the arguments are NULL or the
optional path fails to find an object.
An error will occur if the JSON document is invalid, the
path is invalid or if the path contains a * or wildcard.
JSON_SET can update or insert data, while JSON_REPLACE can
only update, and JSON_INSERT only insert.
Examples
--------
URL: https://mariadb.com/kb/en/json_set/https://mariadb.com/kb/en/json_set/ � 'RJ * Aggregate Functions as Window FunctionsWindow functions were first introduced in MariaDB 10.2.0.
It is possible to use aggregate functions as window
functions. An aggregate function used as a window function
must have the OVER clause. For example, here's COUNT() used
as a window function:
select COUNT(*) over (order by column) from table;
MariaDB currently allows these aggregate functions to be
used as window functions:
AVG
BIT_AND
BIT_OR
BIT_XOR
COUNT
MAX
MIN
STD
STDDEV
STDDEV_POP
STDDEV_SAMP
SUM
VAR_POP
VAR_SAMP
VARIANCE
URL:
https://mariadb.com/kb/en/library/aggregate-functions-as-window-functions/https://mariadb.com/kb/en/library/aggregate-functions-as-window-functions/ � �$ * CUME_DISTThe CUME_DIST() function was first introduced with window
functions in MariaDB 10.2.0.
Syntax
------
CUME_DIST() OVER (
[ PARTITION BY partition_expression ]
[ ORDER BY order_list ]
)
Description
-----------
CUME_DIST() is a window function that returns the cumulative
distribution of a given row. The following formula is used
to calculate the value:
(number of rows
URL: https://mariadb.com/kb/en/cume_dist/https://mariadb.com/kb/en/cume_dist/ , �[����
uT i�(Q� �R a �- SHOW BINLOG EVENTSSyntax
------
SHOW BINLOG EVENTS
[IN 'log_name'] [FROM pos] [LIMIT [offset,] row_count]
Description
-----------
Shows the events in the binary log. If you do not specify
'log_name',
the first binary log is displayed.
Example
SHOW BINLOG EVENTS IN 'mysql_sandbox10019-bin.000002';
+-------------------------------+-----+-------------------+-----------+-------------+------------------------------------------------+
| Log_name | Pos | Event_type | Server_id | End_log_pos |
Info |
+-------------------------------+-----+-------------------+-----------+-------------+------------------------------------------------+
| mysql_sandbox10019-bin.000002 | 4 | Format_desc | 1 | 248
| Server ver: 10.0.19-MariaDB-log, Binlog ver: 4 |
| mysql_sandbox10019-bin.000002 | 248 | Gtid_list | 1 | 273
| [] |
| mysql_sandbox10019-bin.000002 | 273 | Binlog_checkpoint |
1 | 325 | mysql_sandbox10019-bin.000002 |
| mysql_sandbox10019-bin.000002 | 325 | Gtid | 1 | 363 |
GTID 0-1-1 |
| mysql_sandbox10019-bin.000002 | 363 | Query | 1 | 446 |
CREATE DATABASE blog |
| mysql_sandbox10019-bin.000002 | 446 | Gtid | 1 | 484 |
GTID 0-1-2 |
| mysql_sandbox10019-bin.000002 | 484 | Query | 1 | 571 |
use `blog`; CREATE TABLE bb (id INT) |
+-------------------------------+-----+-------------------+-----------+-------------+------------------------------------------------+
URL: https://mariadb.com/kb/en/show-binlog-events/https://mariadb.com/kb/en/show-binlog-events/ b s- SHOW CHARACTER SETSyntax
------
SHOW CHARACTER SET
[LIKE 'pattern' | WHERE expr]
Description
-----------
The SHOW CHARACTER SET statement shows all available
character sets. The LIKE clause, if present on its own,
indicates which character
set names to match. The WHERE and LIKE clauses can be given
to select rows using more general conditions, as discussed
in Extended SHOW.
The same information can be queried from the
information_schema.CHARACTER_SETS table.
See Setting Character Sets and Collations for details on
specifying the character set at the server, database, table
and column levels.
Examples
--------
SHOW CHARACTER SET LIKE 'latin%';
+---------+-----------------------------+-------------------+--------+
| Charset | Description | Default collation | Maxlen |
+---------+-----------------------------+-------------------+--------+
| latin1 | cp1252 West European | latin1_swedish_ci | 1 |
| latin2 | ISO 8859-2 Central European | latin2_general_ci |
1 |
| latin5 | ISO 8859-9 Turkish | latin5_turkish_ci | 1 |
| latin7 | ISO 8859-13 Baltic | latin7_general_ci | 1 |
+---------+-----------------------------+-------------------+--------+
SHOW CHARACTER SET WHERE Maxlen LIKE '2';
+---------+---------------------------+-------------------+--------+
| Charset | Description | Default collation | Maxlen |
+---------+---------------------------+-------------------+--------+
| big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 |
| sjis | Shift-JIS Japanese | sjis_japanese_ci | 2 |
| euckr | EUC-KR Korean | euckr_korean_ci | 2 |
| gb2312 | GB2312 Simplified Chinese | gb2312_chinese_ci | 2
|
| gbk | GBK Simplified Chinese | gbk_chinese_ci | 2 |
| ucs2 | UCS-2 Unicode | ucs2_general_ci | 2 |
| cp932 | SJIS for Windows Japanese | cp932_japanese_ci | 2
|
+---------+---------------------------+-------------------+--------+
URL: https://mariadb.com/kb/en/show-character-set/https://mariadb.com/kb/en/show-character-set/ c 1 SHOW CLIENT_STATISTICSMariaDB 5.2 introduced the User Statistics feature.
Syntax
------
SHOW CLIENT_STATISTICS
Description
-----------
The SHOW CLIENT_STATISTICS statement was introduced in
MariaDB 5.2 as part of the User Statistics feature. It was
removed as a separate statement in MariaDB 10.1.1, but
effectively replaced by the generic SHOW
information_schema_table statement. The
information_schema.CLIENT_STATISTICS table holds statistics
about client connections.
The userstat system variable must be set to 1 to activate
this feature. See the User Statistics and
information_schema.CLIENT_STATISTICS articles for more
information.
Example
From MariaDB 10.0:
SHOW CLIENT_STATISTICS\G
*************************** 1. row
***************************
Client: localhost
Total_connections: 35
Concurrent_connections: 0
Connected_time: 708
Busy_time: 2.5557979999999985
Cpu_time: 0.04123740000000002
Bytes_received: 3883
Bytes_sent: 21595
Binlog_bytes_written: 0
Rows_read: 18
Rows_sent: 115
Rows_deleted: 0
Rows_inserted: 0
Rows_updated: 0
Select_commands: 70
Update_commands: 0
Other_commands: 0
Commit_transactions: 1
Rollback_transactions: 0
Denied_connections: 0
Lost_connections: 0
Access_denied: 0
Empty_queries: 35
URL: https://mariadb.com/kb/en/show-client-statistics/https://mariadb.com/kb/en/show-client-statistics/ d 9
) SHOW COLLATIONSyntax
------
SHOW COLLATION
[LIKE 'pattern' | WHERE expr]
Description
-----------
The output from SHOW COLLATION includes all available
collations. The LIKE clause, if present on its own,
indicates which collation names to match. The WHERE and LIKE
clauses can be given to select rows using more general
conditions, as discussed in Extended SHOW.
The same information can be queried from the
information_schema.COLLATIONS table.
See Setting Character Sets and Collations for details on
specifying the collation at the server, database, table and
column levels.
Examples
--------
SHOW COLLATION LIKE 'latin1%';
+-------------------+---------+----+---------+----------+---------+
| Collation | Charset | Id | Default | Compiled | Sortlen |
+-------------------+---------+----+---------+----------+---------+
| latin1_german1_ci | latin1 | 5 | | Yes | 1 |
| latin1_swedish_ci | latin1 | 8 | Yes | Yes | 1 |
| latin1_danish_ci | latin1 | 15 | | Yes | 1 |
| latin1_german2_ci | latin1 | 31 | | Yes | 2 |
| latin1_bin | latin1 | 47 | | Yes | 1 |
| latin1_general_ci | latin1 | 48 | | Yes | 1 |
| latin1_general_cs | latin1 | 49 | | Yes | 1 |
| latin1_spanish_ci | latin1 | 94 | | Yes | 1 |
+-------------------+---------+----+---------+----------+---------+
SHOW COLLATION WHERE Sortlen LIKE '8' AND Charset LIKE
'utf8';
+--------------------+---------+-----+---------+----------+---------+
| Collation | Charset | Id | Default | Compiled | Sortlen |
+--------------------+---------+-----+---------+----------+---------+
| utf8_unicode_ci | utf8 | 192 | | Yes | 8 |
| utf8_icelandic_ci | utf8 | 193 | | Yes | 8 |
| utf8_latvian_ci | utf8 | 194 | | Yes | 8 |
| utf8_romanian_ci | utf8 | 195 | | Yes | 8 |
| utf8_slovenian_ci | utf8 | 196 | | Yes | 8 |
| utf8_polish_ci | utf8 | 197 | | Yes | 8 |
| utf8_estonian_ci | utf8 | 198 | | Yes | 8 |
| utf8_spanish_ci | utf8 | 199 | | Yes | 8 |
| utf8_swedish_ci | utf8 | 200 | | Yes | 8 |
| utf8_turkish_ci | utf8 | 201 | | Yes | 8 |
| utf8_czech_ci | utf8 | 202 | | Yes | 8 |
| utf8_danish_ci | utf8 | 203 | | Yes | 8 |
| utf8_lithuanian_ci | utf8 | 204 | | Yes | 8 |
| utf8_slovak_ci | utf8 | 205 | | Yes | 8 |
| utf8_spanish2_ci | utf8 | 206 | | Yes | 8 |
| utf8_roman_ci | utf8 | 207 | | Yes | 8 |
| utf8_persian_ci | utf8 | 208 | | Yes | 8 |
| utf8_esperanto_ci | utf8 | 209 | | Yes | 8 |
| utf8_hungarian_ci | utf8 | 210 | | Yes | 8 |
| utf8_sinhala_ci | utf8 | 211 | | Yes | 8 |
| utf8_croatian_ci | utf8 | 213 | | Yes | 8 |
+--------------------+---------+-----+---------+----------+---------+
URL: https://mariadb.com/kb/en/show-collation/https://mariadb.com/kb/en/show-collation/ ~
�
r�� �� $� �� e �' SHOW COLUMNSSyntax
------
SHOW [FULL] {COLUMNS | FIELDS} FROM tbl_name [FROM db_name]
[LIKE 'pattern' | WHERE expr]
Description
-----------
SHOW COLUMNS displays information about the columns in a
given table. It also works for views. The LIKE clause, if
present on its own, indicates which column names to match.
The WHERE and LIKE clauses can be given to select rows using
more general conditions, as discussed in Extended SHOW.
If the data types differ from what you expect them to be
based on a
CREATE TABLE statement, note that MariaDB sometimes changes
data types when you create or alter a table. The conditions
under which this
occurs are described in the Silent Column Changes article.
The FULL keyword causes the output to include the column
collation and comments, as well as the privileges you have
for each column.
You can use db_name.tbl_name as an alternative to the
tbl_name FROM db_name syntax. In other words, these two
statements are equivalent:
SHOW COLUMNS FROM mytable FROM mydb;
SHOW COLUMNS FROM mydb.mytable;
SHOW COLUMNS displays the following values for each table
column:
Field indicates the column name.
Type indicates the column data type.
Collation indicates the collation for non-binary string
columns, or
NULL for other columns. This value is displayed only if you
use the
FULL keyword.
The Null field contains YES if NULL values can be stored in
the column,
NO if not.
The Key field indicates whether the column is indexed:
If Key is empty, the column either is not indexed or is
indexed only as a
secondary column in a multiple-column, non-unique index.
If Key is PRI, the column is a PRIMARY KEY or
is one of the columns in a multiple-column PRIMARY KEY.
If Key is UNI, the column is the first column of a
unique-valued
index that cannot contain NULL values.
If Key is MUL, multiple occurrences of a given value are
allowed
within the column. The column is the first column of a
non-unique index or a
unique-valued index that can contain NULL values.
If more than one of the Key values applies to a given column
of a
table, Key displays the one with the highest priority, in
the order
PRI, UNI, MUL.
A UNIQUE index may be displayed as PRI if
it cannot contain NULL values and there is no
PRIMARY KEY in the table. A UNIQUE index
may display as MUL if several columns form a composite
UNIQUE index; although the combination of the columns is
unique, each column can still hold multiple occurrences of a
given value.
The Default field indicates the default value that is
assigned to the
column.
The Extra field contains any additional information that is
available about a given column.
Value | Description |
AUTO_INCREMENT | The column was created with the
AUTO_INCREMENT keyword. |
PERSISTENT | The column was created with the PERSISTENT
keyword. (New in 5.3) |
VIRTUAL | The column was created with the VIRTUAL keyword.
(New in 5.3) |
on update CURRENT_TIMESTAMP | The column is a TIMESTAMP
column that is automatically updated on INSERT and UPDATE. |
Privileges indicates the privileges you have for the column.
This
value is displayed only if you use the FULL keyword.
Comment indicates any comment the column has. This value is
displayed
only if you use the FULL keyword.
SHOW FIELDS is a synonym for
SHOW COLUMNS. Also DESCRIBE and EXPLAIN can be used as
shortcuts.
You can also list a table's columns with:
mysqlshow db_name tbl_name
See the mysqlshow command for more details.
The DESCRIBE statement provides information similar to SHOW
COLUMNS. The information_schema.COLUMNS table provides
similar, but more complete, information.
The SHOW CREATE TABLE, SHOW TABLE STATUS, and SHOW INDEX
statements also provide information about tables.
Examples
--------
SHOW COLUMNS FROM city;
+------------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+----------+------+-----+---------+----------------+
| Id | int(11) | NO | PRI | NULL | auto_increment |
| Name | char(35) | NO | | | |
| Country | char(3) | NO | UNI | | |
| District | char(20) | YES | MUL | | |
| Population | int(11) | NO | | 0 | |
+------------+----------+------+-----+---------+----------------+
SHOW COLUMNS FROM employees WHERE Type LIKE 'Varchar%';
+---------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------------+-------------+------+-----+---------+-------+
| first_name | varchar(30) | NO | MUL | NULL | |
| last_name | varchar(40) | NO | | NULL | |
| position | varchar(25) | NO | | NULL | |
| home_address | varchar(50) | NO | | NULL | |
| home_phone | varchar(12) | NO | | NULL | |
| employee_code | varchar(25) | NO | UNI | NULL | |
+---------------+-------------+------+-----+---------+-------+
URL: https://mariadb.com/kb/en/show-columns/https://mariadb.com/kb/en/show-columns/ � �$ * NTH_VALUEThe NTH_VALUE() function was first introduced with other
window functions in MariaDB 10.2.
Syntax
------
NTH_VALUE (expr[, num_row]) OVER (
[ PARTITION BY partition_expression ]
[ ORDER BY order_list ]
)
Description
-----------
The NTH_VALUE function returns the value evaluated at row
number num_row of the window frame, starting from 1, or NULL
if the row does not exist.
URL: https://mariadb.com/kb/en/nth_value/https://mariadb.com/kb/en/nth_value/ � �7 + SPIDER_FLUSH_TABLE_MON_CACHESyntax
------
SPIDER_FLUSH_TABLE_MON_CACHE()
Description
-----------
A UDF installed with the Spider Storage Engine, this
function is used for refreshing monitoring server
information. It returns a value of 1.
Examples
--------
SELECT SPIDER_FLUSH_TABLE_MON_CACHE();
+--------------------------------+
| SPIDER_FLUSH_TABLE_MON_CACHE() |
+--------------------------------+
| 1 |
+--------------------------------+
URL: https://mariadb.com/kb/en/spider_flush_table_mon_cache/https://mariadb.com/kb/en/spider_flush_table_mon_cache/ � �' , COLUMN_CHECKThe COLUMN_CHECK function was added in MariaDB 10.0.1.
Syntax
------
COLUMN_CHECK(dyncol_blob);
Description
-----------
Check if dyncol_blob is a valid packed dynamic columns blob.
Return value of 1 means the blob is valid, return value of 0
means it is not.
Rationale:
Normally, one works with valid dynamic column blobs.
Functions like COLUMN_CREATE, COLUMN_ADD, COLUMN_DELETE
always return valid dynamic column blobs. However, if a
dynamic column blob is accidentally truncated, or transcoded
from one character set to another, it will be corrupted.
This function can be used to check if a value in a blob
field is a valid dynamic column blob.
URL: https://mariadb.com/kb/en/column_check/https://mariadb.com/kb/en/column_check/ �
�( , COLUMN_DELETEThe Dynamic columns feature was introduced in MariaDB 5.3.
Syntax
------
COLUMN_DELETE(dyncol_blob, column_nr, column_nr...);
COLUMN_DELETE(dyncol_blob, column_name, column_name...);
Description
-----------
Deletes a dynamic column with the specified name. Multiple
names can be given. The return value is a dynamic column
blob after the modification.
URL: https://mariadb.com/kb/en/column_delete/https://mariadb.com/kb/en/column_delete/ �
�( , COLUMN_EXISTSThe Dynamic columns feature was introduced in MariaDB 5.3.
Syntax
------
COLUMN_EXISTS(dyncol_blob, column_nr);
COLUMN_EXISTS(dyncol_blob, column_name);
Description
-----------
Checks if a column with name column_name exists in
dyncol_blob. If yes, return 1, otherwise return 0. See
dynamic columns for more information.
URL: https://mariadb.com/kb/en/column_exists/https://mariadb.com/kb/en/column_exists/ � ����8SB� 6 �E f �
, SHOW CONTRIBUTORSSyntax
------
SHOW CONTRIBUTORS
Description
-----------
The SHOW CONTRIBUTORS statement displays information about
the companies and people who financially contribute to
MariaDB. For each contributor, it displays Name, Location,
and Comment values. All columns are encoded as latin1.
In MariaDB 5.5 this is in somewhat random order, and the
feature was deprecated.
In MariaDB 10.0.5 it was un-deprecated, and since then
displays all members and sponsors of the MariaDB Foundation
as well as other financial contributors.
Example
SHOW CONTRIBUTORS;
+---------------------+-------------------------------+-------------------------------------------------------------+
| Name | Location | Comment |
+---------------------+-------------------------------+-------------------------------------------------------------+
| Booking.com | https://www.booking.com | Founding member,
Platinum Sponsor of the MariaDB Foundation |
| Alibaba Cloud | https://www.alibabacloud.com/ | Platinum
Sponsor of the MariaDB Foundation |
| Tencent Cloud | https://cloud.tencent.com | Platinum
Sponsor of the MariaDB Foundation |
| Microsoft | https://microsoft.com/ | Platinum Sponsor of
the MariaDB Foundation |
| MariaDB Corporation | https://mariadb.com | Founding
member, Platinum Sponsor of the MariaDB Foundation |
| Visma | https://visma.com | Gold Sponsor of the MariaDB
Foundation |
| DBS | https://dbs.com | Gold Sponsor of the MariaDB
Foundation |
| IBM | https://www.ibm.com | Gold Sponsor of the MariaDB
Foundation |
| Tencent Games | http://game.qq.com/ | Gold Sponsor of the
MariaDB Foundation |
| Nexedi | https://www.nexedi.com | Silver Sponsor of the
MariaDB Foundation |
| Acronis | https://www.acronis.com | Silver Sponsor of the
MariaDB Foundation |
| Verkkokauppa.com | https://www.verkkokauppa.com | Bronze
Sponsor of the MariaDB Foundation |
| Virtuozzo | https://virtuozzo.com | Bronze Sponsor of the
MariaDB Foundation |
| Tencent Game DBA | http://tencentdba.com/about | Bronze
Sponsor of the MariaDB Foundation |
| Tencent TDSQL | http://tdsql.org | Bronze Sponsor of the
MariaDB Foundation |
| Percona | https://www.percona.com/ | Bronze Sponsor of the
MariaDB Foundation |
| Google | USA | Sponsoring encryption, parallel replication
and GTID |
| Facebook | USA | Sponsoring non-blocking API, LIMIT ROWS
EXAMINED etc |
| Ronald Bradford | Brisbane, Australia | EFF contribution
for UC2006 Auction |
| Sheeri Kritzer | Boston, Mass. USA | EFF contribution for
UC2006 Auction |
| Mark Shuttleworth | London, UK. | EFF contribution for
UC2006 Auction |
+---------------------+-------------------------------+-------------------------------------------------------------+
URL: https://mariadb.com/kb/en/show-contributors/https://mariadb.com/kb/en/show-contributors/ g / SHOW CREATE DATABASESyntax
------
SHOW CREATE {DATABASE | SCHEMA} db_name
Description
-----------
Shows the CREATE DATABASE statement that
creates the given database. SHOW CREATE SCHEMA is a synonym
for SHOW CREATE DATABASE. SHOW CREATE DATABASE quotes
database names according to the value of the
sql_quote_show_create server system variable.
Examples
--------
SHOW CREATE DATABASE test;
+----------+-----------------------------------------------------------------+
| Database | Create Database |
+----------+-----------------------------------------------------------------+
| test | CREATE DATABASE `test` /*!40100 DEFAULT CHARACTER
SET latin1 */ |
+----------+-----------------------------------------------------------------+
SHOW CREATE SCHEMA test;
+----------+-----------------------------------------------------------------+
| Database | Create Database |
+----------+-----------------------------------------------------------------+
| test | CREATE DATABASE `test` /*!40100 DEFAULT CHARACTER
SET latin1 */ |
+----------+-----------------------------------------------------------------+
With sql_quote_show_create off:
SHOW CREATE DATABASE test;
+----------+---------------------------------------------------------------+
| Database | Create Database |
+----------+---------------------------------------------------------------+
| test | CREATE DATABASE test /*!40100 DEFAULT CHARACTER SET
latin1 */ |
+----------+---------------------------------------------------------------+
URL: https://mariadb.com/kb/en/show-create-database/https://mariadb.com/kb/en/show-create-database/ h �, SHOW CREATE EVENTSyntax
------
SHOW CREATE EVENT event_name
Description
-----------
This statement displays the CREATE EVENT
statement needed to re-create a given event, as well as the
SQL_MODE that was used when the trigger has been created and
the character set used by the connection.. To find out which
events are present, use SHOW EVENTS.
The output of this statement is unreliably affected by the
sql_quote_show_create server system variable - see
http://bugs.mysql.com/bug.php?id=12719
The information_schema.EVENTS table provides similar, but
more complete, information.
Examples
--------
SHOW CREATE EVENT test.e_daily\G
*************************** 1. row
***************************
Event: e_daily
sql_mode:
time_zone: SYSTEM
Create Event: CREATE EVENT `e_daily`
ON SCHEDULE EVERY 1 DAY
STARTS CURRENT_TIMESTAMP + INTERVAL 6 HOUR
ON COMPLETION NOT PRESERVE
ENABLE
COMMENT 'Saves total number of sessions then
clears the table each day'
DO BEGIN
INSERT INTO site_activity.totals (time, total)
SELECT CURRENT_TIMESTAMP, COUNT(*)
FROM site_activity.sessions;
DELETE FROM site_activity.sessions;
END
character_set_client: latin1
collation_connection: latin1_swedish_ci
Database Collation: latin1_swedish_ci
URL: https://mariadb.com/kb/en/show-create-event/https://mariadb.com/kb/en/show-create-event/ � �& , COLUMN_LISTThe Dynamic columns feature was introduced in MariaDB 5.3.
Syntax
------
COLUMN_LIST(dyncol_blob);
Description
-----------
Since MariaDB 10.0.1, this function returns a
comma-separated list of column names. The names are quoted
with backticks.
Before MariaDB 10.0.1, it returned a comma-separated list of
column numbers, not names.
See dynamic columns for more information.
URL: https://mariadb.com/kb/en/column_list/https://mariadb.com/kb/en/column_list/ ��aJ X �
�<?� �5 i / SHOW CREATE FUNCTIONSyntax
------
SHOW CREATE FUNCTION func_name
Description
-----------
This statement is similar to
SHOW CREATE PROCEDURE but for
stored functions.
The output of this statement is unreliably affected by the
sql_quote_show_create server system variable - see
http://bugs.mysql.com/bug.php?id=12719
Example
MariaDB [test]> SHOW CREATE FUNCTION VatCents\G
*************************** 1. row
***************************
Function: VatCents
sql_mode:
Create Function: CREATE DEFINER=`root`@`localhost` FUNCTION
`VatCents`(price DECIMAL(10,2)) RETURNS int(11)
DETERMINISTIC
BEGIN
DECLARE x INT;
SET x = price * 114;
RETURN x;
END
character_set_client: utf8
collation_connection: utf8_general_ci
Database Collation: latin1_swedish_ci
URL: https://mariadb.com/kb/en/show-create-function/https://mariadb.com/kb/en/show-create-function/ j �. SHOW CREATE PACKAGEOracle-style packages were introduced in MariaDB 10.3.5.
Syntax
------
SHOW CREATE PACKAGE [ db_name . ] package_name
Description
-----------
The SHOW CREATE PACKAGE statement can be used when Oracle
SQL_MODE is set.
Shows the CREATE statement that creates the given package
specification.
Examples
--------
SHOW CREATE PACKAGE employee_tools\G
*************************** 1. row
***************************
Package: employee_tools
sql_mode:
PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,ORACLE,NO_KEY_OPTIONS,NO_TABLE_OPTIONS,NO_FIELD_OPTIONS,NO_AUTO_CREATE_USER
Create Package: CREATE DEFINER="root"@"localhost"
PACKAGE "employee_tools" AS
FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2);
PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2));
PROCEDURE raiseSalaryStd(eid INT);
PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2));
END
character_set_client: utf8
collation_connection: utf8_general_ci
Database Collation: latin1_swedish_ci
URL: https://mariadb.com/kb/en/show-create-package/https://mariadb.com/kb/en/show-create-package/ k 03 SHOW CREATE PACKAGE BODYOracle-style packages were introduced in MariaDB 10.3.5.
Syntax
------
SHOW CREATE PACKAGE BODY [ db_name . ] package_name
Description
-----------
The SHOW CREATE PACKAGE BODY statement can be used when
Oracle SQL_MODE is set.
Shows the CREATE statement that creates the given package
body (i.e. the implementation).
Examples
--------
SHOW CREATE PACKAGE BODY employee_tools\G
*************************** 1. row
***************************
Package body: employee_tools
sql_mode:
PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,ORACLE,NO_KEY_OPTIONS,NO_TABLE_OPTIONS,NO_FIELD_OPTIONS,NO_AUTO_CREATE_USER
Create Package Body: CREATE DEFINER="root"@"localhost"
PACKAGE BODY "employee_tools" AS
stdRaiseAmount DECIMAL(10,2):=500;
PROCEDURE log (eid INT, ecmnt TEXT) AS
BEGIN
INSERT INTO employee_log (id, cmnt) VALUES (eid, ecmnt);
END;
PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2)) AS
eid INT;
BEGIN
INSERT INTO employee (name, salary) VALUES (ename,
esalary);
eid:= last_insert_id();
log(eid, 'hire ' || ename);
END;
FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2) AS
nSalary DECIMAL(10,2);
BEGIN
SELECT salary INTO nSalary FROM employee WHERE id=eid;
log(eid, 'getSalary id=' || eid || ' salary=' ||
nSalary);
RETURN nSalary;
END;
PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2)) AS
BEGIN
UPDATE employee SET salary=salary+amount WHERE id=eid;
log(eid, 'raiseSalary id=' || eid || ' amount=' ||
amount);
END;
PROCEDURE raiseSalaryStd(eid INT) AS
BEGIN
raiseSalary(eid, stdRaiseAmount);
log(eid, 'raiseSalaryStd id=' || eid);
END;
BEGIN
log(0, 'Session ' || connection_id() || ' ' ||
current_user || ' started');
END
character_set_client: utf8
collation_connection: utf8_general_ci
Database Collation: latin1_swedish_ci
URL: https://mariadb.com/kb/en/show-create-package-body/https://mariadb.com/kb/en/show-create-package-body/ l 0 SHOW CREATE PROCEDURESyntax
------
SHOW CREATE PROCEDURE proc_name
Description
-----------
This statement is a MariaDB extension. It returns the exact
string that
can be used to re-create the named stored procedure, as well
as the SQL_MODE that was used when the trigger has been
created and the character set used by the connection.. A
similar
statement, SHOW CREATE FUNCTION,
displays information about stored functions.
Both statements require that you are the owner of the
routine or have the SELECT privilege on the mysql.proc
table. When neither is true, the statements display NULL for
the Create Procedure or Create Function field.
Warning Users with SELECT privileges on mysql.proc or USAGE
privileges on *.* can view the text of routines, even when
they do not have privileges for the function or procedure
itself.
The output of these statements is unreliably affected by the
sql_quote_show_create server system variable - see
http://bugs.mysql.com/bug.php?id=12719
Examples
--------
Here's a comparison of the SHOW CREATE PROCEDURE and SHOW
CREATE FUNCTION statements.
SHOW CREATE PROCEDURE test.simpleproc\G
*************************** 1. row
***************************
Procedure: simpleproc
sql_mode:
Create Procedure: CREATE PROCEDURE `simpleproc`(OUT param1
INT)
BEGIN
SELECT COUNT(*) INTO param1 FROM t;
END
character_set_client: latin1
collation_connection: latin1_swedish_ci
Database Collation: latin1_swedish_ci
SHOW CREATE FUNCTION test.hello\G
*************************** 1. row
***************************
Function: hello
sql_mode:
Create Function: CREATE FUNCTION `hello`(s CHAR(20))
RETURNS CHAR(50)
RETURN CONCAT('Hello, ',s,'!')
character_set_client: latin1
collation_connection: latin1_swedish_ci
Database Collation: latin1_swedish_ci
When the user issuing the statement does not have privileges
on the routine, attempting to CALL the procedure raises
Error 1370.
CALL test.prc1();
Error 1370 (42000): execute command denieed to user
'test_user'@'localhost' for routine 'test'.'prc1'
If the user neither has privilege to the routine nor the
SELECT privilege on mysql.proc table, it raises Error 1305,
informing them that the procedure does not exist.
SHOW CREATE TABLES test.prc1\G
Error 1305 (42000): PROCEDURE prc1 does not exist
URL: https://mariadb.com/kb/en/show-create-procedure/https://mariadb.com/kb/en/show-create-procedure/ Er ��}? q/� � m ]/ SHOW CREATE SEQUENCESequences were introduced in MariaDB 10.3.
Syntax
------
SHOW CREATE SEQUENCE sequence_name;
Description
-----------
Shows the CREATE SEQUENCE statement that created the given
sequence. The statement requires the SELECT privilege for
the table.
Example
CREATE SEQUENCE s1 START WITH 50;
SHOW CREATE SEQUENCE s1\G;
*************************** 1. row
***************************
Table: t1
Create Table: CREATE SEQUENCE `s1` start with 50 minvalue 1
maxvalue 9223372036854775806
increment by 1 cache 1000 nocycle ENGINE=Aria
Notes
If you want to see the underlying table structure used for
the SEQUENCE
you can use SHOW CREATE TABLE on the SEQUENCE. You can also
use SELECT to read the current recorded state of the
SEQUENCE:
CREATE SEQUENCE t1;
SHOW CREATE TABLE s1\G
*************************** 1. row
***************************
Table: s1
Create Table: CREATE TABLE `s1` (
`next_value` bigint(21) NOT NULL COMMENT 'next not cached
value',
`min_value` bigint(21) NOT NULL COMMENT 'min value',
`max_value` bigint(21) NOT NULL COMMENT 'max value',
`start` bigint(21) NOT NULL COMMENT 'start value',
`increment` bigint(21) NOT NULL COMMENT 'increment
value',
`cache` bigint(21) NOT NULL COMMENT 'cache size',
`cycle` tinyint(1) unsigned NOT NULL COMMENT 'cycle
state',
`round` bigint(21) NOT NULL COMMENT 'How many cycles has
been done'
) ENGINE=Aria SEQUENCE=1
SELECT * FROM s1;
+------------+-----------+---------------------+-------+-----------+-------+-------+-------+
| next_value | min_value | max_value | start | increment |
cache | cycle | round |
+------------+-----------+---------------------+-------+-----------+-------+-------+-------+
| 1 | 1 | 9223372036854775806 | 1 | 1 | 1000 | 0 | 0 |
+------------+-----------+---------------------+-------+-----------+-------+-------+-------+
URL: https://mariadb.com/kb/en/show-create-sequence/https://mariadb.com/kb/en/show-create-sequence/ n � , SHOW CREATE TABLESyntax
------
SHOW CREATE TABLE tbl_name
Description
-----------
Shows the CREATE TABLE statement that created the given
table. The statement requires the SELECT privilege for the
table. This statement also works with views and SEQUENCE.
SHOW CREATE TABLE quotes table and
column names according to the value of the
sql_quote_show_create server system variable.
MariaDB and MySQL-specific table options, column options,
and index options are not included in the output of this
statement if the NO_TABLE_OPTIONS, NO_FIELD_OPTIONS and
NO_KEY_OPTIONS SQL_MODE flags are used.
Invalid table options, column options and index options are
normally commented out (note, that it is possible to create
a table with invalid options, by altering a table of a
different engine, where these options were valid). To have
them uncommented, enable IGNORE_BAD_TABLE_OPTIONS SQL_MODE.
Remember that replaying a CREATE TABLE statement with
uncommented invalid options will fail with an error, unless
IGNORE_BAD_TABLE_OPTIONS SQL_MODE is in effect.
Note that SHOW CREATE TABLE is not meant to provide metadata
about a table. It provides information about how the table
was declared, but the real table structure could differ a
bit. For example, if an index has been declared as HASH, the
CREATE TABLE statement returned by SHOW CREATE TABLE will
declare that index as HASH; however, it is possible that the
index is in fact a BTREE, because the storage engine does
not support HASH.
MariaDB 10.2.1 permits TEXT and BLOB data types to be
assigned a DEFAULT value. As a result, from MariaDB 10.2.1,
SHOW CREATE TABLE will append a DEFAULT NULL to nullable
TEXT or BLOB fields if no specific default is provided.
From MariaDB 10.2.2, numbers are no longer quoted in the
DEFAULT clause in SHOW CREATE statement. Previously, MariaDB
quoted numbers.
Examples
--------
SHOW CREATE TABLE t\G
*************************** 1. row
***************************
Table: t
Create Table: CREATE TABLE `t` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`s` char(60) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
With sql_quote_show_create off:
SHOW CREATE TABLE t\G
*************************** 1. row
***************************
Table: t
Create Table: CREATE TABLE t (
id int(11) NOT NULL AUTO_INCREMENT,
s char(60) DEFAULT NULL,
PRIMARY KEY (id)
) ENGINE=InnoDB DEFAULT CHARSET=latin1
Unquoted numeric DEFAULTs, from MariaDB 10.2.2:
CREATE TABLE td (link TINYINT DEFAULT 1);
SHOW CREATE TABLE td\G
*************************** 1. row
***************************
Table: td
Create Table: CREATE TABLE `td` (
`link` tinyint(4) DEFAULT 1
) ENGINE=InnoDB DEFAULT CHARSET=latin1
Quoted numeric DEFAULTs, until MariaDB 10.2.1:
CREATE TABLE td (link TINYINT DEFAULT 1);
SHOW CREATE TABLE td\G
*************************** 1. row
***************************
Table: td
Create Table: CREATE TABLE `td` (
`link` tinyint(4) DEFAULT '1'
) ENGINE=InnoDB DEFAULT CHARSET=latin1
URL: https://mariadb.com/kb/en/show-create-table/https://mariadb.com/kb/en/show-create-table/ �. ���3@ �� o �. SHOW CREATE TRIGGERSyntax
------
SHOW CREATE TRIGGER trigger_name
Description
-----------
This statement shows a CREATE TRIGGER
statement that creates the given trigger, as well as the
SQL_MODE that was used when the trigger has been created and
the character set used by the connection.
The output of this statement is unreliably affected by the
sql_quote_show_create server system variable - see
http://bugs.mysql.com/bug.php?id=12719
Examples
--------
SHOW CREATE TRIGGER example\G
*************************** 1. row
***************************
Trigger: example
sql_mode:
ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,STRICT_ALL_TABLES
,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_
ENGINE_SUBSTITUTION
SQL Original Statement: CREATE DEFINER=`root`@`localhost`
TRIGGER example BEFORE
INSERT ON t FOR EACH ROW
BEGIN
SET NEW.c = NEW.c * 2;
END
character_set_client: cp850
collation_connection: cp850_general_ci
Database Collation: utf8_general_ci
Created: 2016-09-29 13:53:34.35
The Created column was added in MySQL 5.7 and MariaDB 10.2.3
as part of introducing multiple trigger events per action.
URL: https://mariadb.com/kb/en/show-create-trigger/https://mariadb.com/kb/en/show-create-trigger/ p 5+ SHOW CREATE USERSHOW CREATE USER was introduced in MariaDB 10.2.0
Syntax
------
SHOW CREATE USER user_name
Description
-----------
Shows the CREATE USER statement that created the given
user. The statement requires the SELECT privilege for the
mysql database, except for the current user.
Examples
--------
CREATE USER foo4@test require cipher 'text'
issuer 'foo_issuer' subject 'foo_subject';
SHOW CREATE USER foo4@test\G
*************************** 1. row
***************************
CREATE USER 'foo4'@'test'
REQUIRE ISSUER 'foo_issuer'
SUBJECT 'foo_subject'
CIPHER 'text'
User Password Expiry:
CREATE USER 'monty'@'localhost' PASSWORD EXPIRE INTERVAL
120 DAY;
SHOW CREATE USER 'monty'@'localhost';
+------------------------------------------------------------------+
| CREATE USER for monty@localhost |
+------------------------------------------------------------------+
| CREATE USER 'monty'@'localhost' PASSWORD EXPIRE
INTERVAL 120 DAY |
+------------------------------------------------------------------+
URL: https://mariadb.com/kb/en/show-create-user/https://mariadb.com/kb/en/show-create-user/ q �+ SHOW CREATE VIEWSyntax
------
SHOW CREATE VIEW view_name
Description
-----------
This statement shows a CREATE VIEW statement that creates
the given view, as well as the character set used by the
connection when the view was created. This statement
also works with views.
SHOW CREATE VIEW quotes table, column and stored function
names according to the value of the sql_quote_show_create
server system variable.
Examples
--------
SHOW CREATE VIEW example\G
*************************** 1. row
***************************
View: example
Create View: CREATE ALGORITHM=UNDEFINED
DEFINER=`root`@`localhost` SQL
SECURITY DEFINER VIEW `example` AS (select `t`.`id` AS
`id`,`t`.`s` AS `s` from
`t`)
character_set_client: cp850
collation_connection: cp850_general_ci
With sql_quote_show_create off:
SHOW CREATE VIEW example\G
*************************** 1. row
***************************
View: example
Create View: CREATE ALGORITHM=UNDEFINED
DEFINER=root@localhost SQL SECU
RITY DEFINER VIEW example AS (select t.id AS id,t.s AS s
from t)
character_set_client: cp850
collation_connection: cp850_general_ci
URL: https://mariadb.com/kb/en/show-create-view/https://mariadb.com/kb/en/show-create-view/ r B) SHOW DATABASESSyntax
------
SHOW {DATABASES | SCHEMAS}
[LIKE 'pattern' | WHERE expr]
Description
-----------
SHOW DATABASES lists the databases on the MariaDB server
host.
SHOW SCHEMAS is a synonym for
SHOW DATABASES. The LIKE clause, if
present on its own, indicates which database names to match.
The WHERE and LIKE clauses can be given to select rows using
more general conditions, as discussed in Extended SHOW.
You see only those databases for which you have some kind of
privilege, unless you have the global
SHOW DATABASES privilege. You
can also get this list using the mysqlshow command.
If the server was started with the --skip-show-database
option, you cannot use this statement at all unless you have
the
SHOW DATABASES privilege.
Example
SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| test |
+--------------------+
SHOW DATABASES LIKE 'm%';
+---------------+
| Database (m%) |
+---------------+
| mysql |
+---------------+
URL: https://mariadb.com/kb/en/show-databases/https://mariadb.com/kb/en/show-databases/ u ' SHOW ENGINESSyntax
------
SHOW [STORAGE] ENGINES
Description
-----------
SHOW ENGINES displays status information about the server's
storage engines. This is particularly useful for checking
whether a storage
engine is supported, or to see what the default engine is.
SHOW TABLE TYPES is a deprecated synonym.
The information_schema.ENGINES table provides the same
information.
Since storage engines are plugins, different information
about them is also shown in the information_schema.PLUGINS
table and by the SHOW PLUGINS statement.
Note that both MySQL's InnoDB and Percona's XtraDB
replacement are labeled as InnoDB. However, if XtraDB is in
use, it will be specified in the COMMENT field. See XtraDB
and InnoDB. The same applies to FederatedX.
The output consists of the following columns:
Engine indicates the engine's name.
Support indicates whether the engine is installed, and
whether it is the default engine for the current session.
Comment is a brief description.
Transactions, XA and Savepoints indicate whether
transactions, XA transactions and transaction savepoints are
supported by the engine.
Examples
--------
SHOW ENGINES\G
*************************** 1. row
***************************
Engine: InnoDB
Support: DEFAULT
Comment: Supports transactions, row-level locking, and
foreign keys
Transactions: YES
XA: YES
Savepoints: YES
*************************** 2. row
***************************
Engine: CSV
Support: YES
Comment: CSV storage engine
Transactions: NO
XA: NO
Savepoints: NO
*************************** 3. row
***************************
Engine: MyISAM
Support: YES
Comment: MyISAM storage engine
Transactions: NO
XA: NO
Savepoints: NO
*************************** 4. row
***************************
Engine: BLACKHOLE
Support: YES
Comment: /dev/null storage engine (anything you write to it
disappears)
Transactions: NO
XA: NO
Savepoints: NO
*************************** 5. row
***************************
Engine: FEDERATED
Support: YES
Comment: FederatedX pluggable storage engine
Transactions: YES
XA: NO
Savepoints: YES
*************************** 6. row
***************************
Engine: MRG_MyISAM
Support: YES
Comment: Collection of identical MyISAM tables
Transactions: NO
XA: NO
Savepoints: NO
*************************** 7. row
***************************
Engine: ARCHIVE
Support: YES
Comment: Archive storage engine
Transactions: NO
XA: NO
Savepoints: NO
*************************** 8. row
***************************
Engine: MEMORY
Support: YES
Comment: Hash based, stored in memory, useful for temporary
tables
Transactions: NO
XA: NO
Savepoints: NO
*************************** 9. row
***************************
Engine: PERFORMANCE_SCHEMA
Support: YES
Comment: Performance Schema
Transactions: NO
XA: NO
Savepoints: NO
*************************** 10. row
***************************
Engine: Aria
Support: YES
Comment: Crash-safe tables with MyISAM heritage
Transactions: NO
XA: NO
Savepoints: NO
10 rows in set (0.00 sec)
URL: https://mariadb.com/kb/en/show-engines/https://mariadb.com/kb/en/show-engines/ �I L�w ��~ �䶼n ��
s �& SHOW ENGINESyntax
------
SHOW ENGINE engine_name {STATUS | MUTEX}
Description
-----------
SHOW ENGINE displays operational information about a storage
engine. The following statements currently are supported:
SHOW ENGINE INNODB STATUS
SHOW ENGINE INNODB MUTEX
SHOW ENGINE PERFORMANCE_SCHEMA STATUS
If the Sphinx Storage Engine is installed, the following is
also supported:
SHOW ENGINE SPHINX STATUS
See SHOW ENGINE SPHINX STATUS.
Older (and now removed) synonyms were SHOW INNODB STATUS
for SHOW ENGINE INNODB STATUS and
SHOW MUTEX STATUS for
SHOW ENGINE INNODB MUTEX.
SHOW ENGINE BDB LOGS formerly displayed status information
about BDB log files. It was deprecated in MySQL 5.1.12 and
removed in MariaDB and MySQL 5.5, so now produces an error.
SHOW ENGINE INNODB STATUS
SHOW ENGINE INNODB STATUS displays extensive information
from the standard InnoDB Monitor about the state of the
InnoDB storage engine.
See SHOW ENGINE INNODB STATUS for more.
SHOW ENGINE INNODB MUTEX
SHOW ENGINE INNODB MUTEX displays InnoDB mutex statistics.
The statement displays the following output fields:
Type: Always InnoDB.
Name: The source file where the mutex is implemented, and
the line number
in the file where the mutex is created. The line number is
dependent on the MariaDB version.
Status: This field displays the following values if
UNIV_DEBUG was defined at compilation time (for example, in
include/univ.h in the InnoDB part of the source tree). Only
the os_waits value is displayed if UNIV_DEBUG was not
defined. Without UNIV_DEBUG, the information on which the
output is based is insufficient to distinguish regular
mutexes and mutexes that protect
rw-locks (which allow multiple readers or a single writer).
Consequently, the
output may appear to contain multiple rows for the same
mutex.
count indicates how many times the mutex was requested.
spin_waits indicates how many times the spinlock had to run.
spin_rounds indicates the number of spinlock rounds.
(spin_rounds divided by
spin_waits provides the average round count.)
os_waits indicates the number of operating system waits.
This occurs when
the spinlock did not work (the mutex was not locked during
the spinlock and
it was necessary to yield to the operating system and
wait).
os_yields indicates the number of times a the thread trying
to lock a mutex
gave up its timeslice and yielded to the operating system
(on the
presumption that allowing other threads to run will free
the mutex so that
it can be locked).
os_wait_times indicates the amount of time (in ms) spent in
operating system
waits, if the timed_mutexes system variable is 1 (ON). If
timed_mutexes is 0
(OFF), timing is disabled, so os_wait_times is 0.
timed_mutexes is off by
default.
Information from this statement can be used to diagnose
system problems. For
example, large values of spin_waits and spin_rounds may
indicate scalability
problems.
The information_schema.INNODB_MUTEXES table provides similar
information.
SHOW ENGINE PERFORMANCE_SCHEMA STATUS
This statement shows how much memory is used for
performance_schema tables and internal buffers.
The output contains the following fields:
Type: Always performance_schema.
Name: The name of a table, the name of an internal buffer,
or the performance_schema word, followed by a dot and an
attribute. Internal buffers names are enclosed by
parenthesis. performance_schema means that the attribute
refers to the whole database (it is a total).
Status: The value for the attribute.
The following attributes are shown, in this order, for all
tables:
row_size: The memory used for an individual record. This
value will never change.
row_count: The number of rows in the table or buffer. For
some tables, this value depends on a server system variable.
memory: For tables and performance_schema, this is the
result of row_size * row_count.
For internal buffers, the attributes are:
count
size
URL: https://mariadb.com/kb/en/show-engine/https://mariadb.com/kb/en/show-engine/ v �& SHOW ERRORSSyntax
------
SHOW ERRORS [LIMIT [offset,] row_count]
SHOW ERRORS [LIMIT row_count OFFSET offset]
SHOW COUNT(*) ERRORS
Description
-----------
This statement is similar to SHOW WARNINGS, except that
instead of
displaying errors, warnings, and notes, it displays only
errors.
The LIMIT clause has the same syntax as for the
SELECT statement.
The SHOW COUNT(*) ERRORS statement displays the number of
errors. You can also retrieve this number from the
error_count variable.
SHOW COUNT(*) ERRORS;
SELECT @@error_count;
The value of error_count might be greater than the number of
messages displayed by SHOW WARNINGS if the max_error_count
system variable is set so low that not all messages are
stored.
For a list of MariaDB error codes, see MariaDB Error Codes.
Examples
--------
SELECT f();
ERROR 1305 (42000): FUNCTION f does not exist
SHOW COUNT(*) ERRORS;
+-----------------------+
| @@session.error_count |
+-----------------------+
| 1 |
+-----------------------+
SHOW ERRORS;
+-------+------+---------------------------+
| Level | Code | Message |
+-------+------+---------------------------+
| Error | 1305 | FUNCTION f does not exist |
+-------+------+---------------------------+
URL: https://mariadb.com/kb/en/show-errors/https://mariadb.com/kb/en/show-errors/ �9 ��3t� �R t ?4 SHOW ENGINE INNODB STATUSSHOW ENGINE INNODB STATUS is a specific form of the SHOW
ENGINE statement that displays the InnoDB Monitor output,
which is extensive InnoDB information which can be useful in
diagnosing problems.
The following sections are displayed
Status: Shows the timestamp, monitor name and the number of
seconds, or the elapsed time between the current time and
the time the InnoDB Monitor output was last displayed. The
per-second averages are based upon this time.
BACKGROUND THREAD: srv_master_thread lines show work
performed by the main background thread.
SEMAPHORES: Threads waiting for a semaphore and stats on how
the number of times threads have needed a spin or a wait on
a mutex or rw-lock semaphore. If this number of threads is
large, there may be I/O or contention issues. Reducing the
size of the innodb_thread_concurrency system variable may
help if contention is related to thread scheduling. Spin
rounds per wait shows the number of spinlock rounds per OS
wait for a mutex.
LATEST FOREIGN KEY ERROR: Only shown if there has been a
foreign key constraint error, it displays the failed
statement and information about the constraint and the
related tables.
LATEST DETECTED DEADLOCK: Only shown if there has been a
deadlock, it displays the transactions involved in the
deadlock and the statements being executed, held and
required locked and the transaction rolled back to.
TRANSACTIONS: The output of this section can help identify
lock contention, as well as reasons for the deadlocks.
FILE I/O: InnoDB thread information as well as pending I/O
operations and I/O performance statistics.
INSERT BUFFER AND ADAPTIVE HASH INDEX: InnoDB insert buffer
and adaptive hash index status information, including the
number of each type of operation performed, and adaptive
hash index performance.
LOG: InnoDB log information, including current log sequence
number, how far the log has been flushed to disk, the
position at which InnoDB last took a checkpoint, pending
writes and write performance statistics.
BUFFER POOL AND MEMORY: Information on buffer pool pages
read and written, which allows you to see the number of data
file I/O operations performed by your queries. See InnoDB
Buffer Pool for more. Similar information is also available
from the INFORMATION_SCHEMA.INNODB_BUFFER_POOL_STATS table.
ROW OPERATIONS:Information about the main thread, including
the number and performance rate for each type of row
operation.
If the innodb_status_output_locks system variable is set to
1, extended lock information will be displayed.
Example output:
=====================================
2016-09-12 04:42:15 7f226145fb00 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 29 seconds
-----------------
BACKGROUND THREAD
-----------------
srv_master_thread loops: 0 srv_active, 0 srv_shutdown, 527
srv_idle
srv_master_thread log flush and writes: 527
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 4
OS WAIT ARRAY INFO: signal count 4
Mutex spin waits 2, rounds 60, OS waits 2
RW-shared spins 2, rounds 60, OS waits 2
RW-excl spins 0, rounds 0, OS waits 0
Spin rounds per wait: 30.00 mutex, 30.00 RW-shared, 0.00
RW-excl
------------
TRANSACTIONS
------------
Trx id counter 2308
Purge done for trx's n:o < 0 undo n:o < 0 state: running
but idle
History list length 0
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0, not started
MySQL thread id 3, OS thread handle 0x7f226145fb00, query id
4 localhost root init
SHOW ENGINE INNODB STATUS
--------
FILE I/O
--------
I/O thread 0 state: waiting for completed aio requests
(insert buffer thread)
I/O thread 1 state: waiting for completed aio requests (log
thread)
I/O thread 2 state: waiting for completed aio requests (read
thread)
I/O thread 3 state: waiting for completed aio requests (read
thread)
I/O thread 4 state: waiting for completed aio requests (read
thread)
I/O thread 5 state: waiting for completed aio requests (read
thread)
I/O thread 6 state: waiting for completed aio requests
(write thread)
I/O thread 7 state: waiting for completed aio requests
(write thread)
I/O thread 8 state: waiting for completed aio requests
(write thread)
I/O thread 9 state: waiting for completed aio requests
(write thread)
Pending normal aio reads: 0 [0, 0, 0, 0] , aio writes: 0 [0,
0, 0, 0] ,
ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0
Pending flushes (fsync) log: 0; buffer pool: 0
172 OS file reads, 5 OS file writes, 5 OS fsyncs
0.00 reads/s, 0 avg bytes/read, 0.00 writes/s, 0.00 fsyncs/s
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 0, seg size 2, 0 merges
merged operations:
insert 0, delete mark 0, delete 0
discarded operations:
insert 0, delete mark 0, delete 0
0.00 hash searches/s, 0.00 non-hash searches/s
---
LOG
---
Log sequence number 1616829
Log flushed up to 1616829
Pages flushed up to 1616829
Last checkpoint at 1616829
Max checkpoint age 80826164
Checkpoint age target 78300347
Modified age 0
Checkpoint age 0
0 pending log writes, 0 pending chkp writes
8 log i/o's done, 0.00 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total memory allocated 140771328; in additional pool
allocated 0
Total memory allocated by read views 88
Internal hash tables (constant factor + variable factor)
Adaptive hash index 2217568 (2213368 + 4200)
Page hash 139112 (buffer pool 0 only)
Dictionary cache 630703 (554768 + 75935)
File system 817648 (812272 + 5376)
Lock system 333232 (332872 + 360)
Recovery system 0 (0 + 0)
Dictionary memory allocated 75935
Buffer pool size 8191
Buffer pool size, bytes 134201344
Free buffers 8037
Database pages 154
Old database pages 0
Modified db pages 0
Percent of dirty pages(LRU & free pages): 0.000
Max dirty pages percent: 75.000
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 0, not young 0
0.00 youngs/s, 0.00 non-youngs/s
Pages read 154, created 0, written 1
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
No buffer pool page gets since the last printout
Pages read ahead 0.00/s, evicted without access 0.00/s,
Random read ahead 0.00/s
LRU len: 154, unzip_LRU len: 0
I/O sum[0]:cur[0], unzip sum[0]:cur[0]
--------------
ROW OPERATIONS
--------------
0 queries inside InnoDB, 0 queries in queue
0 read views open inside InnoDB
0 RW transactions active inside InnoDB
0 RO transactions active inside InnoDB
0 out of 1000 descriptors used
Main thread process no. 3337, id 139784957703936, state:
sleeping
Number of rows inserted 0, updated 0, deleted 0, read 0
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s
Number of system rows inserted 0, updated 0, deleted 0, read
0
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s
----------------------------
END OF INNODB MONITOR OUTPUT
============================
URL: https://mariadb.com/kb/en/show-engine-innodb-status/https://mariadb.com/kb/en/show-engine-innodb-status/ ��F� �� w q& SHOW EVENTSSyntax
------
SHOW EVENTS [{FROM | IN} schema_name]
[LIKE 'pattern' | WHERE expr]
Description
-----------
Shows information about Event Manager events (created with
CREATE EVENT). Requires the EVENT privilege. Without any
arguments, SHOW EVENTS lists all of the events in the
current schema:
SELECT CURRENT_USER(), SCHEMA();
+----------------+----------+
| CURRENT_USER() | SCHEMA() |
+----------------+----------+
| jon@ghidora | myschema |
+----------------+----------+
SHOW EVENTS\G
*************************** 1. row
***************************
Db: myschema
Name: e_daily
Definer: jon@ghidora
Time zone: SYSTEM
Type: RECURRING
Execute at: NULL
Interval value: 10
Interval field: SECOND
Starts: 2006-02-09 10:41:23
Ends: NULL
Status: ENABLED
Originator: 0
character_set_client: latin1
collation_connection: latin1_swedish_ci
Database Collation: latin1_swedish_ci
To see the event action, use SHOW CREATE EVENT instead, or
look at the information_schema.EVENTS table.
To see events for a specific schema, use the FROM clause.
For example, to see events for the test schema, use the
following statement:
SHOW EVENTS FROM test;
The LIKE clause, if present, indicates which event names to
match. The WHERE clause can be given to select rows using
more general conditions, as discussed in Extended Show.
URL: https://mariadb.com/kb/en/show-events/https://mariadb.com/kb/en/show-events/ x ' SHOW EXPLAINThe SHOW EXPLAIN command is a new feature in MariaDB 10.0.0.
Command description
The SHOW EXPLAIN command allows one to get an EXPLAIN (that
is, a
description of a query plan) of a query running in a certain
thread.
The syntax is:
SHOW EXPLAIN FOR ;
which will produce an EXPLAIN output for the query that
thread number thread_id is running. The thread id can be
obtained with SHOW PROCESSLIST.
SHOW EXPLAIN FOR 1;
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
| id | select_type | table | type | possible_keys | key |
key_len | ref | rows | Extra |
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
| 1 | SIMPLE | tbl | index | NULL | a | 5 | NULL | 1000107 |
Using index |
+------+-------------+-------+-------+---------------+------+---------+------+---------+-------------+
1 row in set, 1 warning (0.00 sec)
The output is always accompanied with a warning which shows
the query the
target thread is running (this shows what the EXPLAIN is
for):
SHOW WARNINGS;
+-------+------+------------------------+
| Level | Code | Message |
+-------+------+------------------------+
| Note | 1003 | select sum(a) from tbl |
+-------+------+------------------------+
1 row in set (0.00 sec)
Possible errors
The output can be only produced if the target thread is
currently running a
query, which has a ready query plan. If this is not the
case, the output will
be:
SHOW EXPLAIN FOR 2;
ERROR 1932 (HY000): Target is not running an EXPLAINable
command
You will get this error when:
the target thread is not running a command for which one can
run EXPLAIN
the target thread is running a command for which one can run
EXPLAIN, but
there is no query plan yet (for example, tables are open and
locks are
acquired before the query plan is produced)
Differences between SHOW EXPLAIN and EXPLAIN outputs
Background
In MySQL, EXPLAIN execution takes a slightly different route
from the way
the real query (typically the SELECT) is optimized. This is
unfortunate,
and has caused a number of bugs in EXPLAIN. (For example,
see
MDEV-326, MDEV-410, and
lp:1013343.
lp:992942 is not directly
about EXPLAIN, but it also would not have existed if MySQL
didn't try to delete
parts of a query plan in the middle of the query)
SHOW EXPLAIN examines a running SELECT, and hence its output
may be
slightly different from what EXPLAIN SELECT would produce.
We did our best
to make sure that either the difference is negligible, or
SHOW EXPLAIN's
output is closer to reality than EXPLAIN's output.
List of recorded differences
SHOW EXPLAIN may have Extra='no matching row in const
table', where EXPLAIN would produce Extra='Impossible
WHERE ...'
For queries with subqueries, SHOW EXPLAIN may print
select_type==PRIMARY where regular EXPLAIN used to print
select_type==SIMPLE, or vice versa.
Required permissions
Running SHOW EXPLAIN requires the same permissions as
running SHOW PROCESSLIST would.
URL: https://mariadb.com/kb/en/show-explain/https://mariadb.com/kb/en/show-explain/ z �/ SHOW FUNCTION STATUSSyntax
------
SHOW FUNCTION STATUS
[LIKE 'pattern' | WHERE expr]
Description
-----------
This statement is similar to
SHOW PROCEDURE STATUS but for
stored functions.
The LIKE clause, if present on its own, indicates which
function names to match.
The WHERE and LIKE clauses can be given to select rows using
more general conditions, as discussed in Extended SHOW.
The information_schema.ROUTINES table contains more detailed
information.
Examples
--------
Showing all stored functions:
SHOW FUNCTION STATUS\G
*************************** 1. row
***************************
Db: test
Name: VatCents
Type: FUNCTION
Definer: root@localhost
Modified: 2013-06-01 12:40:31
Created: 2013-06-01 12:40:31
Security_type: DEFINER
Comment:
character_set_client: utf8
collation_connection: utf8_general_ci
Database Collation: latin1_swedish_ci
Stored functions whose name starts with 'V':
SHOW FUNCTION STATUS LIKE 'V%' \G
*************************** 1. row
***************************
Db: test
Name: VatCents
Type: FUNCTION
Definer: root@localhost
Modified: 2013-06-01 12:40:31
Created: 2013-06-01 12:40:31
Security_type: DEFINER
Comment:
character_set_client: utf8
collation_connection: utf8_general_ci
Database Collation: latin1_swedish_ci
Stored functions with a security type of 'DEFINER':
SHOW FUNCTION STATUS WHERE Security_type LIKE 'DEFINER'
\G
*************************** 1. row
***************************
Db: test
Name: VatCents
Type: FUNCTION
Definer: root@localhost
Modified: 2013-06-01 12:40:31
Created: 2013-06-01 12:40:31
Security_type: DEFINER
Comment:
character_set_client: utf8
collation_connection: utf8_general_ci
Database Collation: latin1_swedish_ci
URL: https://mariadb.com/kb/en/show-function-status/https://mariadb.com/kb/en/show-function-status/ �K�B �`�� �� { �& SHOW GRANTSUsers
Syntax
------
SHOW GRANTS [FOR user]
Description
-----------
This statement lists the GRANT statement or
statements that must be issued to duplicate the privileges
that are granted to
a MariaDB user account. The account is named using the same
format as for the
GRANT statement; for example,
'jeffrey'@'localhost'. If you specify only the user name
part
of the account name, a host name part of '%' is used. For
additional information about specifying account names, see
GRANT.
SHOW GRANTS FOR 'root'@'localhost';
+---------------------------------------------------------------------+
| Grants for root@localhost |
+---------------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH
GRANT OPTION |
+---------------------------------------------------------------------+
To list the privileges granted to the account that you are
using to
connect to the server, you can use any of the following
statements:
SHOW GRANTS;
SHOW GRANTS FOR CURRENT_USER;
SHOW GRANTS FOR CURRENT_USER();
If SHOW GRANTS FOR CURRENT_USER (or any
of the equivalent syntaxes) is used in DEFINER context (such
as within a stored procedure that is defined with
SQL SECURITY DEFINER), the grants displayed are those of
the
definer and not the invoker.
Note that the DELETE HISTORY privilege, introduced in
MariaDB 10.3.4, is displayed as DELETE VERSIONING ROWS when
running SHOW GRANTS (MDEV-17655).
Roles
Roles were introduced in MariaDB 10.0.5.
Syntax
------
SHOW GRANTS [FOR role]
Description
-----------
From MariaDB 10.0.5, SHOW GRANTS can also be used to view
the privileges granted to a role.
Example
SHOW GRANTS FOR journalist;
+------------------------------------------+
| Grants for journalist |
+------------------------------------------+
| GRANT USAGE ON *.* TO 'journalist' |
| GRANT DELETE ON `test`.* TO 'journalist' |
+------------------------------------------+
URL: https://mariadb.com/kb/en/show-grants/https://mariadb.com/kb/en/show-grants/ |
�% SHOW INDEXSyntax
------
SHOW {INDEX | INDEXES | KEYS}
FROM tbl_name [FROM db_name]
[WHERE expr]
Description
-----------
SHOW INDEX returns table index information. The format
resembles that of the SQLStatistics call in ODBC.
You can use db_name.tbl_name as an alternative to the
tbl_name FROM db_name syntax. These two statements are
equivalent:
SHOW INDEX FROM mytable FROM mydb;
SHOW INDEX FROM mydb.mytable;
SHOW KEYS and SHOW INDEXES are synonyms for SHOW INDEX.
You can also list a table's indexes with the following
command:
mysqlshow -k db_name tbl_name
See mysqlshow for more details.
The information_schema.STATISTICS table stores similar
information.
The following fields are returned by SHOW INDEX.
Field | Description |
Table | Table name |
Non_unique | 1 if the index permits duplicate values, 0 if
values must be unique. |
Key_name | Index name. The primary key is always named
PRIMARY. |
Seq_in_index | The column's sequence in the index,
beginning with 1. |
Column_name | Column name. |
Collation | Either A, if the column is sorted in ascending
order in the index, or NULL if it's not sorted. |
Cardinality | Estimated number of unique values in the
index. The cardinality statistics are calculated at various
times, and can help the optimizer make improved decisions. |
Sub_part | NULL if the entire column is included in the
index, or the number of included characters if not. |
Packed | NULL if the index is not packed, otherwise how the
index is packed. |
Null | NULL if NULL values are permitted in the column, an
empty string if NULL's are not permitted. |
Index_type | The index type, which can be BTREE, FULLTEXT,
HASH or RTREE. See Storage Engine Index Types. |
Comment | Other information, such as whether the index is
disabled. |
Index_comment | Contents of the COMMENT attribute when the
index was created. |
The WHERE and LIKE clauses can be given to select rows using
more general conditions, as discussed in Extended SHOW.
Examples
--------
CREATE TABLE IF NOT EXISTS `employees_example` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`first_name` varchar(30) NOT NULL,
`last_name` varchar(40) NOT NULL,
`position` varchar(25) NOT NULL,
`home_address` varchar(50) NOT NULL,
`home_phone` varchar(12) NOT NULL,
`employee_code` varchar(25) NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `employee_code` (`employee_code`),
KEY `first_name` (`first_name`,`last_name`)
) ENGINE=Aria;
INSERT INTO `employees_example` (`first_name`, `last_name`,
`position`, `home_address`, `home_phone`, `employee_code`)
VALUES
('Mustapha', 'Mond', 'Chief Executive Officer', '692
Promiscuous Plaza', '326-555-3492', 'MM1'),
('Henry', 'Foster', 'Store Manager', '314 Savage
Circle', '326-555-3847', 'HF1'),
('Bernard', 'Marx', 'Cashier', '1240 Ambient
Avenue', '326-555-8456', 'BM1'),
('Lenina', 'Crowne', 'Cashier', '281 Bumblepuppy
Boulevard', '328-555-2349', 'LC1'),
('Fanny', 'Crowne', 'Restocker', '1023 Bokanovsky
Lane', '326-555-6329', 'FC1'),
('Helmholtz', 'Watson', 'Janitor', '944 Soma
Court', '329-555-2478', 'HW1');
SHOW INDEXES FROM employees_example;
+-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name
| Collation | Cardinality | Sub_part | Packed | Null |
Index_type | Comment | Index_comment |
+-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| employees_example | 0 | PRIMARY | 1 | id | A | 7 | NULL |
NULL | | BTREE | | |
| employees_example | 0 | employee_code | 1 | employee_code
| A | 7 | NULL | NULL | | BTREE | | |
| employees_example | 1 | first_name | 1 | first_name | A |
NULL | NULL | NULL | | BTREE | | |
| employees_example | 1 | first_name | 2 | last_name | A |
NULL | NULL | NULL | | BTREE | | |
+-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
URL: https://mariadb.com/kb/en/show-index/https://mariadb.com/kb/en/show-index/ � 8�&l �
} ' SHOW LOCALESSHOW LOCALES was introduced as part of the Information
Schema plugin extension in MariaDB 10.1.1.
SHOW LOCALES is used to return locales information as part
of the Locales plugin. While the information_schema.LOCALES
table has 8 columns, the SHOW LOCALES statement will only
display 4 of them:
Example
SHOW LOCALES;
+-----+-------+-------------------------------------+------------------------+
| Id | Name | Description | Error_Message_Language |
+-----+-------+-------------------------------------+------------------------+
| 0 | en_US | English - United States | english |
| 1 | en_GB | English - United Kingdom | english |
| 2 | ja_JP | Japanese - Japan | japanese |
| 3 | sv_SE | Swedish - Sweden | swedish |
...
URL: https://mariadb.com/kb/en/show-locales/https://mariadb.com/kb/en/show-locales/ ~ F- SHOW MASTER STATUSSyntax
------
SHOW MASTER STATUS
Description
-----------
Provides status information about the binary log files of
the master.
This statement requires the SUPER or the REPLICATION_CLIENT
privilege.
To see information about the current GTIDs in the binary
log, use the
gtid_binlog_pos variable.
Example
SHOW MASTER STATUS;
+--------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+--------------------+----------+--------------+------------------+
| mariadb-bin.000016 | 475 | | |
+--------------------+----------+--------------+------------------+
SELECT @@global.gtid_binlog_pos;
+--------------------------+
| @@global.gtid_binlog_pos |
+--------------------------+
| 0-1-2 |
+--------------------------+
URL: https://mariadb.com/kb/en/show-master-status/https://mariadb.com/kb/en/show-master-status/ o+ SHOW OPEN TABLESSyntax
------
SHOW OPEN TABLES [FROM db_name]
[LIKE 'pattern' | WHERE expr]
Description
-----------
SHOW OPEN TABLES lists the non-TEMPORARY
tables that are currently open in the table cache. See
http://dev.mysql.com/doc/refman/5.1/en/table-cache.html.
The FROM and LIKE clauses may be used.
The FROM
clause, if present, restricts the tables shown to those
present in the
db_name database.
The LIKE clause, if
present on its own, indicates which table names to match.
The WHERE and LIKE clauses can be given to select rows using
more general conditions, as discussed in Extended SHOW.
The following information is returned:
Column | Description |
Database | Database name. |
Name | Table name. |
In_use | Number of table instances being used. |
Name_locked | 1 if the table is name-locked, e.g. if it is
being dropped or renamed, otherwise 0. |
Before MariaDB 5.5, each use of, for example, LOCK TABLE ...
WRITE would increment In_use for that table. With the
implementation of the metadata locking improvements in
MariaDB 5.5, LOCK TABLE... WRITE acquires a strong MDL lock,
and concurrent connections will wait on this MDL lock, so
any subsequent LOCK TABLE... WRITE will not increment
In_use.
Example
SHOW OPEN TABLES;
+----------+---------------------------+--------+-------------+
| Database | Table | In_use | Name_locked |
+----------+---------------------------+--------+-------------+
...
| test | xjson | 0 | 0 |
| test | jauthor | 0 | 0 |
| test | locks | 1 | 0 |
...
+----------+---------------------------+--------+-------------+
URL: https://mariadb.com/kb/en/show-open-tables/https://mariadb.com/kb/en/show-open-tables/ � �3 SHOW PACKAGE BODY STATUSOracle-style packages were introduced in MariaDB 10.3.5.
Syntax
------
SHOW PACKAGE BODY STATUS
[LIKE 'pattern' | WHERE expr]
Description
-----------
The SHOW PACKAGE BODY STATUS statement returns
characteristics of stored package bodies (implementations),
such as the database, name, type, creator, creation and
modification dates, and character set information. A similar
statement, SHOW PACKAGE STATUS, displays information about
stored package specifications.
The LIKE clause, if present, indicates which package names
to match. The WHERE and LIKE clauses can be given to select
rows using more general conditions, as discussed in Extended
SHOW.
The ROUTINES table in the INFORMATION_SCHEMA database
contains more detailed information.
Examples
--------
SHOW PACKAGE BODY STATUS LIKE 'pkg1'\G
*************************** 1. row
***************************
Db: test
Name: pkg1
Type: PACKAGE BODY
Definer: root@localhost
Modified: 2018-02-27 14:44:14
Created: 2018-02-27 14:44:14
Security_type: DEFINER
Comment: This is my first package body
character_set_client: utf8
collation_connection: utf8_general_ci
Database Collation: latin1_swedish_ci
URL: https://mariadb.com/kb/en/show-package-body-status/https://mariadb.com/kb/en/show-package-body-status/ � �. SHOW PACKAGE STATUSOracle-style packages were introduced in MariaDB 10.3.5.
Syntax
------
SHOW PACKAGE STATUS
[LIKE 'pattern' | WHERE expr]
Description
-----------
The SHOW PACKAGE STATUS statement returns characteristics of
stored package specifications, such as the database, name,
type, creator, creation and modification dates, and
character set information. A similar statement, SHOW PACKAGE
BODY STATUS, displays information about stored package
bodies (i.e. implementations).
The LIKE clause, if present, indicates which package names
to match. The WHERE and LIKE clauses can be given to select
rows using more general conditions, as discussed in Extended
SHOW.
The ROUTINES table in the INFORMATION_SCHEMA database
contains more detailed information.
Examples
--------
SHOW PACKAGE STATUS LIKE 'pkg1'\G
*************************** 1. row
***************************
Db: test
Name: pkg1
Type: PACKAGE
Definer: root@localhost
Modified: 2018-02-27 14:38:15
Created: 2018-02-27 14:38:15
Security_type: DEFINER
Comment: This is my first package
character_set_client: utf8
collation_connection: utf8_general_ci
Database Collation: latin1_swedish_ci
URL: https://mariadb.com/kb/en/show-package-status/https://mariadb.com/kb/en/show-package-status/ � �
'��`� T�)ĵ �- � �' SHOW PLUGINSSyntax
------
SHOW PLUGINS;
Description
-----------
SHOW PLUGINS displays information about installed plugins.
The Library column indicates the plugin library - if it is
NULL, the plugin is built-in and cannot be uninstalled.
The PLUGINS table in the information_schema database
contains more detailed information.
For specific information about storage engines (a particular
type of plugin), see the information_schema.ENGINES table
and the SHOW ENGINES statement.
Examples
--------
SHOW PLUGINS;
+----------------------------+----------+--------------------+-------------+---------+
| Name | Status | Type | Library | License |
+----------------------------+----------+--------------------+-------------+---------+
| binlog | ACTIVE | STORAGE ENGINE | NULL | GPL |
| mysql_native_password | ACTIVE | AUTHENTICATION | NULL |
GPL |
| mysql_old_password | ACTIVE | AUTHENTICATION | NULL | GPL
|
| MRG_MyISAM | ACTIVE | STORAGE ENGINE | NULL | GPL |
| MyISAM | ACTIVE | STORAGE ENGINE | NULL | GPL |
| CSV | ACTIVE | STORAGE ENGINE | NULL | GPL |
| MEMORY | ACTIVE | STORAGE ENGINE | NULL | GPL |
| FEDERATED | ACTIVE | STORAGE ENGINE | NULL | GPL |
| PERFORMANCE_SCHEMA | ACTIVE | STORAGE ENGINE | NULL | GPL
|
| Aria | ACTIVE | STORAGE ENGINE | NULL | GPL |
| InnoDB | ACTIVE | STORAGE ENGINE | NULL | GPL |
| INNODB_TRX | ACTIVE | INFORMATION SCHEMA | NULL | GPL |
...
| INNODB_SYS_FOREIGN | ACTIVE | INFORMATION SCHEMA | NULL |
GPL |
| INNODB_SYS_FOREIGN_COLS | ACTIVE | INFORMATION SCHEMA |
NULL | GPL |
| SPHINX | ACTIVE | STORAGE ENGINE | NULL | GPL |
| ARCHIVE | ACTIVE | STORAGE ENGINE | NULL | GPL |
| BLACKHOLE | ACTIVE | STORAGE ENGINE | NULL | GPL |
| FEEDBACK | DISABLED | INFORMATION SCHEMA | NULL | GPL |
| partition | ACTIVE | STORAGE ENGINE | NULL | GPL |
| pam | ACTIVE | AUTHENTICATION | auth_pam.so | GPL |
+----------------------------+----------+--------------------+-------------+---------+
URL: https://mariadb.com/kb/en/show-plugins/https://mariadb.com/kb/en/show-plugins/ � �. SHOW PLUGINS SONAMEMariaDB 10.0.2
SHOW PLUGINS SONAME was introduced in MariaDB 10.0.2
Syntax
------
SHOW PLUGINS SONAME { library | LIKE 'pattern' | WHERE
expr };
Description
-----------
SHOW PLUGINS SONAME displays information about compiled-in
and all server plugins in the plugin_dir directory,
including plugins that haven't been installed.
Examples
--------
SHOW PLUGINS SONAME 'ha_example.so';
+----------+---------------+----------------+---------------+---------+
| Name | Status | Type | Library | License |
+----------+---------------+----------------+---------------+---------+
| EXAMPLE | NOT INSTALLED | STORAGE ENGINE | ha_example.so |
GPL |
| UNUSABLE | NOT INSTALLED | DAEMON | ha_example.so | GPL |
+----------+---------------+----------------+---------------+---------+
There is also a corresponding information_schema table,
called ALL_PLUGINS, which contains more complete
information.
URL: https://mariadb.com/kb/en/show-plugins-soname/https://mariadb.com/kb/en/show-plugins-soname/ � a * SHOW PRIVILEGESSyntax
------
SHOW PRIVILEGES
Description
-----------
SHOW PRIVILEGES shows the list of system privileges that
the MariaDB server supports. The exact list of privileges
depends on the version of your server.
Note that the Delete history privilege displays as Delete
versioning rows (MDEV-20382).
Examples
--------
SHOW PRIVILEGES;
+-------------------------+---------------------------------------+-------------------------------------------------------+
| Privilege | Context | Comment |
+-------------------------+---------------------------------------+-------------------------------------------------------+
| Alter | Tables | To alter the table |
| Alter routine | Functions,Procedures | To alter or drop
stored functions/procedures |
| Create | Databases,Tables,Indexes | To create new
databases and tables |
| Create routine | Databases | To use CREATE
FUNCTION/PROCEDURE |
| Create temporary tables | Databases | To use CREATE
TEMPORARY TABLE |
| Create view | Tables | To create new views |
| Create user | Server Admin | To create new users |
| Delete | Tables | To delete existing rows |
| Delete versioning rows | Tables | To delete versioning
table historical rows |
| Drop | Databases,Tables | To drop databases, tables, and
views |
| Event | Server Admin | To create, alter, drop and execute
events |
| Execute | Functions,Procedures | To execute stored
routines |
| File | File access on server | To read and write files on
the server |
| Grant option | Databases,Tables,Functions,Procedures | To
give to other users those privileges you possess |
| Index | Tables | To create or drop indexes |
| Insert | Tables | To insert data into tables |
| Lock tables | Databases | To use LOCK TABLES (together
with SELECT privilege) |
| Process | Server Admin | To view the plain text of
currently executing queries |
| Proxy | Server Admin | To make proxy user possible |
| References | Databases,Tables | To have references on
tables |
| Reload | Server Admin | To reload or refresh tables, logs
and privileges |
| Replication client | Server Admin | To ask where the slave
or master servers are |
| Replication slave | Server Admin | To read binary log
events from the master |
| Select | Tables | To retrieve rows from table |
| Show databases | Server Admin | To see all databases with
SHOW DATABASES |
| Show view | Tables | To see views with SHOW CREATE VIEW |
| Shutdown | Server Admin | To shut down the server |
| Super | Server Admin | To use KILL thread, SET GLOBAL,
CHANGE MASTER, etc. |
| Trigger | Tables | To use triggers |
| Create tablespace | Server Admin | To create/alter/drop
tablespaces |
| Update | Tables | To update existing rows |
| Usage | Server Admin | No privileges - allow connect only
|
+-------------------------+---------------------------------------+-------------------------------------------------------+
URL: https://mariadb.com/kb/en/show-privileges/https://mariadb.com/kb/en/show-privileges/ � � �� ��
� �. SHOW PROCEDURE CODESyntax
------
SHOW PROCEDURE CODE proc_name
Description
-----------
This statement is a MariaDB extension that is available only
for servers that
have been built with debugging support. It displays a
representation of the
internal implementation of the named stored procedure. A
similar statement,
SHOW FUNCTION CODE, displays
information about stored functions.
Both statements require that you be the owner of the routine
or have
SELECT access to the mysql.proc table.
If the named routine is available, each statement produces a
result
set. Each row in the result set corresponds to one
"instruction" in
the routine. The first column is Pos, which is an ordinal
number
beginning with 0. The second column is Instruction, which
contains an
SQL statement (usually changed from the original source), or
a
directive which has meaning only to the stored-routine
handler.
Examples
--------
DELIMITER //
CREATE PROCEDURE p1 ()
BEGIN
DECLARE fanta INT DEFAULT 55;
DROP TABLE t2;
LOOP
INSERT INTO t3 VALUES (fanta);
END LOOP;
END//
Query OK, 0 rows affected (0.00 sec)
SHOW PROCEDURE CODE p1//
+-----+----------------------------------------+
| Pos | Instruction |
+-----+----------------------------------------+
| 0 | set fanta@0 55 |
| 1 | stmt 9 "DROP TABLE t2" |
| 2 | stmt 5 "INSERT INTO t3 VALUES (fanta)" |
| 3 | jump 2 |
+-----+----------------------------------------+
URL: https://mariadb.com/kb/en/show-procedure-code/https://mariadb.com/kb/en/show-procedure-code/ � \0 SHOW PROCEDURE STATUSSyntax
------
SHOW PROCEDURE STATUS
[LIKE 'pattern' | WHERE expr]
Description
-----------
This statement is a MariaDB extension. It returns
characteristics of a stored
procedure, such as the database, name, type, creator,
creation and modification
dates, and character set information. A similar statement,
SHOW FUNCTION STATUS, displays
information about stored functions.
The LIKE clause, if present, indicates which procedure or
function names to match. The WHERE and LIKE clauses can be
given to select rows using more general conditions, as
discussed in Extended SHOW.
The ROUTINES table in the INFORMATION_SCHEMA database
contains more detailed information.
Examples
--------
SHOW PROCEDURE STATUS LIKE 'p1'\G
*************************** 1. row
***************************
Db: test
Name: p1
Type: PROCEDURE
Definer: root@localhost
Modified: 2010-08-23 13:23:03
Created: 2010-08-23 13:23:03
Security_type: DEFINER
Comment:
character_set_client: latin1
collation_connection: latin1_swedish_ci
Database Collation: latin1_swedish_ci
URL: https://mariadb.com/kb/en/show-procedure-status/https://mariadb.com/kb/en/show-procedure-status/ � q/ SHOW RELAYLOG EVENTSSyntax
------
SHOW RELAYLOG ['connection_name'] EVENTS
[IN 'log_name'] [FROM pos] [LIMIT [offset,] row_count]
Description
-----------
On replication slaves this command shows the events in the
relay log. If 'log_name' is not specified, the first relay
log is shown.
Syntax for the LIMIT clause is the same as for SELECT ...
LIMIT.
Using the LIMIT clause is highly recommended because the
SHOW RELAYLOG EVENTS command returns the complete contents
of the relay log, which can be quite large.
This command does not return events related to setting user
and system variables. If you need those, use mysqlbinlog.
On the replication master, this command does nothing.
connection_name
connection_name was added as part of multi-source
replication added in MariaDB 10.0.1
If there is only one nameless master, or the default master
(as specified by the default_master_connection system
variable) is intended, connection_name can be omitted. If
provided, the SHOW RELAYLOG statement will apply to the
specified master. connection_name is case-insensitive.
URL: https://mariadb.com/kb/en/show-relaylog-events/https://mariadb.com/kb/en/show-relaylog-events/ � ^+ SHOW SLAVE HOSTSSyntax
------
SHOW SLAVE HOSTS
Description
-----------
This command is run on the master and displays a list of
replication slaves that are currently registered with it.
Only slaves started with the --report-host=host_name option
are visible in this list.
The list is displayed on any server (not just the master
server). The output
looks like this:
SHOW SLAVE HOSTS;
+------------+-----------+------+-----------+
| Server_id | Host | Port | Master_id |
+------------+-----------+------+-----------+
| 192168010 | iconnect2 | 3306 | 192168011 |
| 1921680101 | athena | 3306 | 192168011 |
+------------+-----------+------+-----------+
Server_id: The unique server ID of the slave server, as
configured in the server's option file, or on the command
line with --server-id=value.
Host: The host name of the slave server, as configured in
the server's option file, or on the command line with
--report-host=host_name. Note that this can differ from the
machine name as configured in the operating system.
Port: The port the slave server is listening on.
Master_id: The unique server ID of the master server that
the slave server is replicating from.
Some MariaDB and MySQL versions report another variable,
rpl_recovery_rank. This
variable was never used, and was eventually removed in
MariaDB 10.1.2 and MySQL 5.6.
URL: https://mariadb.com/kb/en/show-slave-hosts/https://mariadb.com/kb/en/show-slave-hosts/ x��
�� �T/ �� � �+ SHOW PROCESSLISTSyntax
------
SHOW [FULL] PROCESSLIST
Description
-----------
SHOW PROCESSLIST shows you which threads are running. You
can also get this information from the
information_schema.PROCESSLIST table or the mysqladmin
processlist command. If you have the
PROCESS privilege, you can see all threads.
Otherwise, you can see only your own threads (that is,
threads associated with
the MariaDB account that you are using). If you do not use
the
FULL keyword, only the first 100 characters of each
statement are shown in the Info field.
The columns shown in SHOW PROCESSLIST
are:
Name | Description | Introduced |
ID | The client's process ID. | |
USER | The username associated with the process. | |
HOST | The host the client is connected to. | |
DB | The default database of the process (NULL if no
default). | |
COMMAND | The command type. See Thread Command Values. | |
TIME | The amount of time, in seconds, the process has been
in its current state. For a slave SQL thread before MariaDB
10.1, this is the time in seconds between the last
replicated event's timestamp and the slave machine's real
time. | |
STATE | See Thread States. | |
INFO | The statement being executed. | |
PROGRESS | The total progress of the process (0-100%) (see
Progress Reporting). | MariaDB 5.3 |
See TIME_MS column in information_schema.PROCESSLIST for
differences in the TIME column between MariaDB and MySQL.
The information_schema.PROCESSLIST table contains the
following additional columns:
Name | Description | Introduced |
TIME_MS | The amount of time, in milliseconds, the process
has been in its current state. | MariaDB 5.1 |
STAGE | The stage the process is currently in. |
MariaDB 5.3 |
MAX_STAGE | The maximum number of stages. | MariaDB 5.3 |
PROGRESS | The progress of the process within the current
stage (0-100%). | MariaDB 5.3 |
MEMORY_USED | The amount of memory used by the process. |
MariaDB 10.0.1 |
EXAMINED_ROWS | The number of rows the process has examined.
| MariaDB 10.0.1 |
QUERY_ID | Query ID. | MariaDB 10.0.5 |
Note that the PROGRESS field from the information schema,
and the PROGRESS field from SHOW PROCESSLIST display
different results. SHOW PROCESSLIST shows the total
progress, while the information schema shows the progress
for the current stage only.
Threads can be killed using their thread_id, or, since
MariaDB 10.0.5, their query_id, with the KILL statement.
Since queries on this table are locking, if the
performance_schema is enabled, you may want to query the
THREADS table instead.
Examples
--------
From MariaDB 5.1.x
SHOW FULL PROCESSLIST;
+---------+-------+-----------+------+---------+------+-------+-----------------------+
| Id | User | Host | db | Command | Time | State | Info |
+---------+-------+-----------+------+---------+------+-------+-----------------------+
| 1988880 | dbart | localhost | NULL | Query | 0 | NULL |
SHOW FULL PROCESSLIST |
+---------+-------+-----------+------+---------+------+-------+-----------------------+
SELECT * FROM information_schema.processlist;
+---------+-------+-----------+------+---------+------+-----------+----------------------------------------------+---------+
| ID | USER | HOST | DB | COMMAND | TIME | STATE | INFO |
TIME_MS |
+---------+-------+-----------+------+---------+------+-----------+----------------------------------------------+---------+
| 1988880 | dbart | localhost | NULL | Query | 0 | executing
| SELECT * FROM information_schema.processlist | 0.444 |
+---------+-------+-----------+------+---------+------+-----------+----------------------------------------------+---------+
From MariaDB 5.5.x
SHOW FULL PROCESSLIST;
+-----+------+-----------+------+---------+------+-------+-----------------------+----------+
| Id | User | Host | db | Command | Time | State | Info |
Progress |
+-----+------+-----------+------+---------+------+-------+-----------------------+----------+
| 126 | root | localhost | NULL | Query | 0 | NULL | SHOW
FULL PROCESSLIST | 0.000 |
+-----+------+-----------+------+---------+------+-------+-----------------------+----------+
SELECT * FROM information_schema.processlist;
+-----+--------+-----------+------+---------+------+-----------+----------------------------------------------+---------+-------+-----------+----------+
| ID | USER | HOST | DB | COMMAND | TIME | STATE | INFO |
TIME_MS | STAGE | MAX_STAGE | PROGRESS |
+-----+--------+-----------+------+---------+------+-----------+----------------------------------------------+---------+-------+-----------+----------+
| 126 | root | localhost | NULL | Query | 0 | executing |
SELECT * FROM information_schema.processlist | 344.718 | 0 |
0 | 0.000 |
+-----+--------+-----------+------+---------+------+-----------+----------------------------------------------+---------+-------+-----------+----------+
From MariaDB 10.0.x
SHOW PROCESSLIST;
+----+-----------------+-----------+------+---------+------+------------------------+------------------+----------+
| Id | User | Host | db | Command | Time | State | Info |
Progress |
+----+-----------------+-----------+------+---------+------+------------------------+------------------+----------+
| 2 | event_scheduler | localhost | NULL | Daemon | 2693 |
Waiting on empty queue | NULL | 0.000 |
| 4 | root | localhost | NULL | Query | 0 | Table lock |
SHOW PROCESSLIST | 0.000 |
+----+-----------------+-----------+------+---------+------+------------------------+------------------+----------+
URL: https://mariadb.com/kb/en/show-processlist/https://mariadb.com/kb/en/show-processlist/ *<`fi �q � �' SHOW PROFILESyntax
------
SHOW PROFILE [type [, type] ... ]
[FOR QUERY n]
[LIMIT row_count [OFFSET offset]]
type:
ALL
| BLOCK IO
| CONTEXT SWITCHES
| CPU
| IPC
| MEMORY
| PAGE FAULTS
| SOURCE
| SWAPS
Description
-----------
The SHOW PROFILE and
SHOW PROFILES statements display profiling
information that indicates resource usage for statements
executed during the
course of the current session.
Profiling is controlled by the profiling session variable,
which has a default value of 0 (OFF). Profiling is enabled
by setting profiling to 1 or ON:
SET profiling = 1;
SHOW PROFILES displays a list of the most recent statements
sent to the master. The size of the list is controlled by
the
profiling_history_size session variable, which has a default
value of 15. The maximum value is 100. Setting the value to
0 has the practical effect of disabling profiling.
All statements are profiled except SHOW PROFILES and
SHOW PROFILE, so you will find neither of those statements
in the profile list. Malformed statements are profiled. For
example,
SHOW PROFILING is an illegal statement, and a syntax error
occurs if you try to execute it, but it will show up in the
profiling list.
SHOW PROFILE displays detailed information about a single
statement. Without the FOR QUERY n clause, the output
pertains to the most recently executed statement. If
FOR QUERY n is included,
SHOW PROFILE displays information for statement n. The
values of n correspond to
the Query_ID values displayed by SHOW PROFILES.
The LIMIT row_count clause may be given to limit the
output to row_count rows. If LIMIT is given,
OFFSET offset may be added to begin the output offset
rows into the full set of rows.
By default, SHOW PROFILE displays Status and Duration
columns. The Status values are like the State values
displayed by
SHOW PROCESSLIST,
although there might be some minor differences in
interpretation for
the two statements for some status values (see
http://dev.mysql.com/doc/refman/5.6/en/thread-information.html).
Optional type values may be specified to display specific
additional
types of information:
ALL displays all information
BLOCK IO displays counts for block input and output
operations
CONTEXT SWITCHES displays counts for voluntary and
involuntary context switches
CPU displays user and system CPU usage times
IPC displays counts for messages sent and received
MEMORY is not currently implemented
PAGE FAULTS displays counts for major and minor page faults
SOURCE displays the names of functions from the source code,
together with the name and line number of the file in which
the function occurs
SWAPS displays swap counts
Profiling is enabled per session. When a session ends, its
profiling information is lost.
The information_schema.PROFILING table contains similar
information.
Examples
--------
SELECT @@profiling;
+-------------+
| @@profiling |
+-------------+
| 0 |
+-------------+
SET profiling = 1;
USE test;
DROP TABLE IF EXISTS t1;
CREATE TABLE T1 (id INT);
SHOW PROFILES;
+----------+------------+--------------------------+
| Query_ID | Duration | Query |
+----------+------------+--------------------------+
| 1 | 0.00009200 | SELECT DATABASE() |
| 2 | 0.00023800 | show databases |
| 3 | 0.00018900 | show tables |
| 4 | 0.00014700 | DROP TABLE IF EXISTS t1 |
| 5 | 0.24476900 | CREATE TABLE T1 (id INT) |
+----------+------------+--------------------------+
SHOW PROFILE;
+----------------------+----------+
| Status | Duration |
+----------------------+----------+
| starting | 0.000042 |
| checking permissions | 0.000044 |
| creating table | 0.244645 |
| After create | 0.000013 |
| query end | 0.000003 |
| freeing items | 0.000016 |
| logging slow query | 0.000003 |
| cleaning up | 0.000003 |
+----------------------+----------+
SHOW PROFILE FOR QUERY 4;
+--------------------+----------+
| Status | Duration |
+--------------------+----------+
| starting | 0.000126 |
| query end | 0.000004 |
| freeing items | 0.000012 |
| logging slow query | 0.000003 |
| cleaning up | 0.000002 |
+--------------------+----------+
SHOW PROFILE CPU FOR QUERY 5;
+----------------------+----------+----------+------------+
| Status | Duration | CPU_user | CPU_system |
+----------------------+----------+----------+------------+
| starting | 0.000042 | 0.000000 | 0.000000 |
| checking permissions | 0.000044 | 0.000000 | 0.000000 |
| creating table | 0.244645 | 0.000000 | 0.000000 |
| After create | 0.000013 | 0.000000 | 0.000000 |
| query end | 0.000003 | 0.000000 | 0.000000 |
| freeing items | 0.000016 | 0.000000 | 0.000000 |
| logging slow query | 0.000003 | 0.000000 | 0.000000 |
| cleaning up | 0.000003 | 0.000000 | 0.000000 |
+----------------------+----------+----------+------------+
URL: https://mariadb.com/kb/en/show-profile/https://mariadb.com/kb/en/show-profile/ � , SHOW TABLE STATUSSyntax
------
SHOW TABLE STATUS [{FROM | IN} db_name]
[LIKE 'pattern' | WHERE expr]
Description
-----------
SHOW TABLE STATUS works like
SHOW TABLES, but provides more extensive information about
each non-TEMPORARY table.
The LIKE clause, if present on its own, indicates which
table names to
match. The WHERE and LIKE clauses can be given to select
rows using more general conditions, as discussed in Extended
SHOW.
The following information is returned:
Column | Description |
Name | Table name. |
Engine | Table storage engine. |
Version | Version number from the table's .frm file. |
Row_format | Row format (see InnoDB, Aria and MyISAM row
formats). |
Rows | Number of rows in the table. Some engines, such as
XtraDB and InnoDB may store an estimate. |
Avg_row_length | Average row length in the table. |
Data_length | For InnoDB/XtraDB, the index size, in pages,
multiplied by the page size. For Aria and MyISAM, length of
the data file, in bytes. For MEMORY, the approximate
allocated memory. |
Max_data_length | Maximum length of the data file, ie the
total number of bytes that could be stored in the table. Not
used in XtraDB and InnoDB. |
Index_length | Length of the index file. |
Data_free | Bytes allocated but unused. For InnoDB tables in
a shared tablespace, the free space of the shared tablespace
with small safety margin. An estimate in the case of
partitioned tables - see the PARTITIONS table. |
Auto_increment | Next AUTO_INCREMENT value. |
Create_time | Time the table was created. |
Update_time | Time the table was last updated. On Windows,
the timestamp is not updated on update, so MyISAM values
will be inaccurate. In InnoDB, if shared tablespaces are
used, will be NULL, while buffering can also delay the
update, so the value will differ from the actual time of the
last UPDATE, INSERT or DELETE. |
Check_time | Time the table was last checked. Not kept by
all storage engines, in which case will be NULL. |
Collation | Character set and collation. |
Checksum | Live checksum value, if any. |
Create_options | Extra CREATE TABLE options. |
Comment | Table comment provided when MariaDB created the
table. |
Similar information can be found in the
information_schema.TABLES table as well as by using
mysqlshow:
mysqlshow --status db_name
Example
show table status\G
*************************** 1. row
***************************
Name: bus_routes
Engine: InnoDB
Version: 10
Row_format: Dynamic
Rows: 5
Avg_row_length: 3276
Data_length: 16384
Max_data_length: 0
Index_length: 0
Data_free: 0
Auto_increment: NULL
Create_time: 2017-05-24 11:17:46
Update_time: NULL
Check_time: NULL
Collation: latin1_swedish_ci
Checksum: NULL
Create_options:
Comment:
URL: https://mariadb.com/kb/en/show-table-status/https://mariadb.com/kb/en/show-table-status/ "a �82S Syntax
------
SHOW SLAVE ["connection_name"] STATUS
or
SHOW ALL SLAVES STATUS
Description
-----------
This statement is to be run on a slave and provides status
information on essential parameters of the replication slave
threads.
This statement requires the SUPER or the REPLICATION_CLIENT
privilege.
Multi-source
MariaDB 10.0 introduced the FULL and "connection_name"
options to
allow you to connect to many masters at the same time.
ALL SLAVES gives you a list of all connections to the
master.
The rows will be sorted according to Connection_name.
If you specify a connection_name, you only get the
information about that
connection. If connection_name is not used, then the name
set by default_master_connection is used. If the connection
name doesn't exist you will get an error:
There is no master connection for 'xxx'.
Column descriptions
Name | Description | Added |
Connection_name | Name of the master connection. Returned
with SHOW ALL SLAVES STATUS only. | MariaDB 10.0 |
Slave_SQL_State | State of SQL thread. Returned with SHOW
ALL SLAVES STATUS only. See Slave SQL Thread States. |
MariaDB 10.0 |
Slave_IO_State | State of I/O thread. See Slave I/O Thread
States. | MariaDB 10.0 |
Master_host | Master host that the slave is connected to. |
|
Master_user | Account user name being used to connect to the
master. | |
Master_port | The port being used to connect to the master.
| |
Connect_Retry | Time in seconds between retries to connect.
The default is 60. The CHANGE MASTER TO statement can set
this. The master-retry-count option determines the maximum
number of reconnection attempts. | |
Master_Log_File | Name of the master binary log file that
the I/O thread is currently reading from. | |
Read_Master_Log_Pos | Position up to which the I/O thread
has read in the current master binary log file. | |
Relay_Log_File | Name of the relay log file that the SQL
thread is currently processing. | |
Relay_Log_Pos | Position up to which the SQL thread has
finished processing in the current relay log file. | |
Relay_Master_Log_File | Name of the master binary log file
that contains the most recent event executed by the SQL
thread. | |
Slave_IO_Running | Whether the slave I/O thread is running
and connected (Yes), running but not connected to a master
(Connecting) or not running (No). | |
Slave_SQL_Running | Whether or not the SQL thread is
running. | |
Replicate_Do_DB | Databases specified for replicating with
the replicate_do_db option. | |
Replicate_Ignore_DB | Databases specified for ignoring with
the replicate_ignore_db option. | |
Replicate_Do_Table | Tables specified for replicating with
the replicate_do_table option. | |
Replicate_Ignore_Table | Tables specified for ignoring with
the replicate_ignore_table option. | |
Replicate_Wild_Do_Table | Tables specified for replicating
with the replicate_wild_do_table option. | |
Replicate_Wild_Ignore_Table | Tables specified for ignoring
with the replicate_wild_ignore_table option. | |
Last_Errno | Alias for Last_SQL_Errno (see below) | |
Last Error | Alias for Last_SQL_Error (see below) | |
Skip_Counter | Number of events that a slave skips from the
master, as recorded in the sql_slave_skip_counter system
variable. | |
Exec_Master_Log_Pos | Position up to which the SQL thread
has processed in the current master binary log file. Can be
used to start a new slave from a current slave with the
CHANGE MASTER TO ... MASTER_LOG_POS option. | |
Relay_Log_Space | Total size of all relay log files
combined. | |
Until_Condition | | |
Until_Log_File | The MASTER_LOG_FILE value of the START
SLAVE UNTIL condition. | |
Until_Log_Pos | The MASTER_LOG_POS value of the START SLAVE
UNTIL condition. | |
Master_SSL_Allowed | Whether an SSL connection is permitted
(Yes), not permitted (No) or permitted but without the slave
having SSL support enabled (Ignored) | |
Master_SSL_CA_File | The MASTER_SSL_CA option of the CHANGE
MASTER TO statement. | |
Master_SSL_CA_Path | The MASTER_SSL_CAPATH option of the
CHANGE MASTER TO statement. | |
Master_SSL_Cert | The MASTER_SSL_CERT option of the CHANGE
MASTER TO statement. | |
Master_SSL_Cipher | The MASTER_SSL_CIPHER option of the
CHANGE MASTER TO statement. | |
Master_SSL_Key | The MASTER_SSL_KEY option of the CHANGE
MASTER TO statement. | |
Seconds_Behind_Master | Difference between the timestamp
logged on the master for the event that the slave is
currently processing, and the current timestamp on the
slave. Zero if the slave is not currently processing an
event. From MariaDB 10.0.23 and MariaDB 10.1.9, with
parallel replication, seconds_behind_master is updated only
after transactions commit. | |
Master_SSL_Verify_Server_Cert | The
MASTER_SSL_VERIFY_SERVER_CERT option of the CHANGE MASTER TO
statement. | |
Last_IO_Errno | Error code of the most recent error that
caused the I/O thread to stop (also recorded in the slave's
error log). 0 means no error. RESET SLAVE or RESET MASTER
will reset this value. | |
Last_IO_Error | Error message of the most recent error that
caused the I/O thread to stop (also recorded in the slave's
error log). An empty string means no error. RESET SLAVE or
RESET MASTER will reset this value. | |
Last_SQL_Errno | Error code of the most recent error that
caused the SQL thread to stop (also recorded in the slave's
error log). 0 means no error. RESET SLAVE or RESET MASTER
will reset this value. | |
Last_SQL_Error | Error message of the most recent error that
caused the SQL thread to stop (also recorded in the slave's
error log). An empty string means no error. RESET SLAVE or
RESET MASTER will reset this value. | |
Replicate_Ignore_Server_Ids | List of server_ids that are
currently being ignored for replication purposes, or an
empty string for none, as specified in the IGNORE_SERVER_IDS
option of the CHANGE MASTER TO statement. | |
Master_Server_Id | The master's server_id value. | |
Master_SSL_Crl | The MASTER_SSL_CRL option of the CHANGE
MASTER TO statement. | MariaDB 10.0 |
Master_SSL_Crlpath | The MASTER_SSL_CRLPATH option of the
CHANGE MASTER TO statement. | MariaDB 10.0 |
Using_Gtid | Whether or not global transaction ID's are
being used for replication (can be No, Slave_Pos, or
Current_Pos). | MariaDB 10.0.2 |
Gtid_IO_Pos | Current global transaction ID value. | MariaDB
10.0.2 |
Retried_transactions | Number of retried transactions for
this connection. Returned with SHOW ALL SLAVES STATUS only.
| MariaDB 10.0 |
Max_relay_log_size | Max relay log size for this connection.
Returned with SHOW ALL SLAVES STATUS only. | MariaDB 10.0 |
Executed_log_entries | How many log entries the slave has
executed. Returned with SHOW ALL SLAVES STATUS only. |
MariaDB 10.0 |
Slave_received_heartbeats | How many heartbeats we have got
from the master. Returned with SHOW ALL SLAVES STATUS only.
| MariaDB 10.0 |
Slave_heartbeat_period | How often to request a heartbeat
packet from the master (in seconds). Returned with SHOW ALL
SLAVES STATUS only. | MariaDB 10.0 |
Gtid_Slave_Pos | GTID of the last event group replicated on
a slave server, for each replication domain, as stored in
the gtid_slave_pos system variable. Returned with SHOW ALL
SLAVES STATUS only. | MariaDB 10.0 |
SQL_Delay | Value specified by MASTER_DELAY in CHANGE MASTER
(or 0 if none). | MariaDB 10.2.3 |
SQL_Remaining_Delay | When the slave is delaying the
execution of an event due to MASTER_DELAY, this is the
number of seconds of delay remaining before the event will
be applied. Otherwise, the value is NULL. | MariaDB 10.2.3 |
Slave_SQL_Running_State | The state of the SQL driver
threads, same as in SHOW PROCESSLIST. When the slave is
delaying the execution of an event due to MASTER_DELAY, this
field displays: "Waiting until MASTER_DELAY seconds after
master executed event". | MariaDB 10.2.3 |
Slave_DDL_Groups | This status variable counts the
occurrence of DDL statements. This is a slave-side counter
for optimistic parallel replication. | MariaDB 10.3.7 |
Slave_Non_Trans��ћ �eactional_Groups | This status variable counts
the occurrence of non-transactional event groups. This is a
slave-side counter for optimistic parallel replication. |
MariaDB 10.3.7 |
Slave_Transactional_Groups | This status variable counts the
occurrence of transactional event groups. This is a
slave-side counter for optimistic parallel replication. |
MariaDB 10.3.7 |
Examples
--------
If you issue this statement using the mysql client,
you can use a \G statement terminator rather than a
semicolon to
obtain a more readable vertical layout.
SHOW SLAVE STATUS\G
*************************** 1. row
***************************
Slave_IO_State: Waiting for master to send event
Master_Host: db01.example.com
Master_User: replicant
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mariadb-bin.000010
Read_Master_Log_Pos: 548
Relay_Log_File: relay-bin.000004
Relay_Log_Pos: 837
Relay_Master_Log_File: mariadb-bin.000010
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 548
Relay_Log_Space: 1497
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 101
Master_SSL_Crl:
Master_SSL_Crlpath:
Using_Gtid: No
Gtid_IO_Pos:
MariaDB [(none)]> SHOW ALL SLAVES STATUS\G
*************************** 1. row
***************************
Connection_name:
Slave_SQL_State: Slave has read all relay log; waiting for
the slave I/O thread to update it
Slave_IO_State: Waiting for master to send event
Master_Host: db01.example.com
Master_User: replicant
Master_Port: 3306
Connect_Retry: 60
Master_Log_File: mariadb-bin.000010
Read_Master_Log_Pos: 3608
Relay_Log_File: relay-bin.000004
Relay_Log_Pos: 3897
Relay_Master_Log_File: mariadb-bin.000010
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 3608
Relay_Log_Space: 4557
Until_Condition: None
Until_Log_File:
Until_Log_Pos: 0
Master_SSL_Allowed: No
Master_SSL_CA_File:
Master_SSL_CA_Path:
Master_SSL_Cert:
Master_SSL_Cipher:
Master_SSL_Key:
Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
Last_IO_Errno: 0
Last_IO_Error:
Last_SQL_Errno: 0
Last_SQL_Error:
Replicate_Ignore_Server_Ids:
Master_Server_Id: 101
Master_SSL_Crl:
Master_SSL_Crlpath:
Using_Gtid: No
Gtid_IO_Pos:
Retried_transactions: 0
Max_relay_log_size: 104857600
Executed_log_entries: 40
Slave_received_heartbeats: 11
Slave_heartbeat_period: 1800.000
Gtid_Slave_Pos: 0-101-2320
You can also access some of the variables directly from
status variables:
SET @@default_master_connection="test" ;
show status like "%slave%"
Variable_name Value
Com_show_slave_hosts 0
Com_show_slave_status 0
Com_start_all_slaves 0
Com_start_slave 0
Com_stop_all_slaves 0
Com_stop_slave 0
Rpl_semi_sync_slave_status OFF
Slave_connections 0
Slave_heartbeat_period 1800.000
Slave_open_temp_tables 0
Slave_received_heartbeats 0
Slave_retried_transactions 0
Slave_running OFF
Slaves_connected 0
Slaves_running 1
URL: https://mariadb.com/kb/en/show-slave-status/https://mariadb.com/kb/en/generated-columns/ c, WcC� Syntax
------
SHOW [GLOBAL | SESSION] STATUS
[LIKE 'pattern' | WHERE expr]
Description
-----------
SHOW STATUS provides server status information. This
information also can be obtained using the mysqladmin
extended-status command, or by querying the Information
Schema GLOBAL_STATUS and SESSION_STATUS tables.
The LIKE clause, if present, indicates which variable names
to match. The WHERE clause can be given to select rows using
more general conditions.
With the GLOBAL modifier, SHOW STATUS
displays the status values for all connections to MariaDB.
With
SESSION, it displays the status values
for the current connection. If no modifier is present, the
default is
SESSION. LOCAL is a synonym for
SESSION. If you see a lot of 0 values, the reason is
probably that you have used SHOW STATUS with a new
connection instead of SHOW GLOBAL STATUS.
Some status variables have only a global value. For these,
you get the
same value for both GLOBAL and SESSION.
See Server Status Variables for a full list, scope and
description of the variables that can be viewed with SHOW
STATUS.
The LIKE clause, if present on its own, indicates which
variable name to match.
The WHERE and LIKE clauses can be given to select rows using
more general conditions, as discussed in Extended SHOW.
Examples
--------
Full output from MariaDB 10.1.17:
SHOW GLOBAL STATUS;
+--------------------------------------------------------------+----------------------------------------+
| Variable_name | Value |
+--------------------------------------------------------------+----------------------------------------+
| Aborted_clients | 0 |
| Aborted_connects | 0 |
| Access_denied_errors | 0 |
| Acl_column_grants | 0 |
| Acl_database_grants | 2 |
| Acl_function_grants | 0 |
| Acl_procedure_grants | 0 |
| Acl_proxy_users | 2 |
| Acl_role_grants | 0 |
| Acl_roles | 0 |
| Acl_table_grants | 0 |
| Acl_users | 6 |
| Aria_pagecache_blocks_not_flushed | 0 |
| Aria_pagecache_blocks_unused | 15706 |
| Aria_pagecache_blocks_used | 0 |
| Aria_pagecache_read_requests | 0 |
| Aria_pagecache_reads | 0 |
| Aria_pagecache_write_requests | 0 |
| Aria_pagecache_writes | 0 |
| Aria_transaction_log_syncs | 0 |
| Binlog_commits | 0 |
| Binlog_group_commits | 0 |
| Binlog_group_commit_trigger_count | 0 |
| Binlog_group_commit_trigger_lock_wait | 0 |
| Binlog_group_commit_trigger_timeout | 0 |
| Binlog_snapshot_file | |
| Binlog_snapshot_position | 0 |
| Binlog_bytes_written | 0 |
| Binlog_cache_disk_use | 0 |
| Binlog_cache_use | 0 |
| Binlog_stmt_cache_disk_use | 0 |
| Binlog_stmt_cache_use | 0 |
| Busy_time | 0.000000 |
| Bytes_received | 432 |
| Bytes_sent | 15183 |
| Com_admin_commands | 1 |
| Com_alter_db | 0 |
| Com_alter_db_upgrade | 0 |
| Com_alter_event | 0 |
| Com_alter_function | 0 |
| Com_alter_procedure | 0 |
| Com_alter_server | 0 |
| Com_alter_table | 0 |
| Com_alter_tablespace | 0 |
| Com_analyze | 0 |
| Com_assign_to_keycache | 0 |
| Com_begin | 0 |
| Com_binlog | 0 |
| Com_call_procedure | 0 |
| Com_change_db | 0 |
| Com_change_master | 0 |
| Com_check | 0 |
| Com_checksum | 0 |
| Com_commit | 0 |
| Com_compound_sql | 0 |
| Com_create_db | 0 |
| Com_create_event | 0 |
| Com_create_function | 0 |
| Com_create_index | 0 |
| Com_create_procedure | 0 |
| Com_create_role | 0 |
| Com_create_server | 0 |
| Com_create_table | 0 |
| Com_create_temporary_table | 0 |
| Com_create_trigger | 0 |
| Com_create_udf | 0 |
| Com_create_user | 0 |
| Com_create_view | 0 |
| Com_dealloc_sql | 0 |
| Com_delete | 0 |
| Com_delete_multi | 0 |
| Com_do | 0 |
| Com_drop_db | 0 |
| Com_drop_event | 0 |
| Com_drop_function | 0 |
| Com_drop_index | 0 |
| Com_drop_procedure | 0 |
| Com_drop_role | 0 |
| Com_drop_server | 0 |
| Com_drop_table | 0 |
| Com_drop_temporary_table | 0 |
| Com_drop_trigger | 0 |
| Com_drop_user | 0 |
| Com_drop_view | 0 |
| Com_empty_query | 0 |
| Com_execute_sql | 0 |
| Com_flush | 0 |
| Com_get_diagnostics | 0 |
| Com_grant | 0 |
| Com_grant_role | 0 |
| Com_ha_close | 0 |
| Com_ha_open | 0 |
| Com_ha_read | 0 |
| Com_help | 0 |
| Com_insert | 0 |
| Com_insert_select | 0 |
| Com_install_plugin | 0 |
| Com_kill | 0 |
| Com_load | 0 |
| Com_lock_tables | 0 |
| Com_optimize | 0 |
| Com_preload_keys | 0 |
| Com_prepare_sql | 0 |
| Com_purge | 0 |
| Com_purge_before_date | 0 |
| Com_release_savepoint | 0 |
| Com_rename_table | 0 |
| Com_rename_user | 0 |
| Com_repair | 0 |
| Com_replace | 0 |
| Com_replace_select | 0 |
| Com_reset | 0 |
| Com_resignal | 0 |
| Com_revoke | 0 |
| Com_revoke_all | 0 |
| Com_revoke_role | 0 |
| Com_rollback | 0 |
| Com_rollback_to_savepoint | 0 |
| Com_savepoint | 0 |
| Com_select | 1 |
| Com_set_option | 0 |
| Com_show_authors | 0 |
| Com_show_binlog_events | 0 |
| Com_show_binlogs | 0 |
| Com_show_charsets | 0 |
| Com_show_collations | 0 |
| Com_show_contributors | 0 |
| Com_show_create_db | 0 |
| Com_show_create_event | 0 |
| Com_show_create_func | 0 |
| Com_show_create_proc | 0 |
| Com_show_create_table | 0 |
| Com_show_create_trigger | 0 |
| Com_show_databases | 0 |
| Com_show_engine_logs | 0 |
| Com_show_engine_mutex | 0 |
| Com_show_engine_status | 0 |
| Com_show_errors | 0 |
| Com_show_events | 0 |
| Com_show_explain | 0 |
| Com_show_fields | 0 |
| Com_show_function_status | 0 |
| Com_show_generic | 0 |
| Com_show_grants | 0 |
| Com_show_keys | 0 |
| Com_show_master_status | 0 |
| Com_show_open_tables | 0 |
| Com_show_plugins | 0 |
| Com_show_privileges | 0 |
| Com_show_procedure_status | 0 |
| Com_show_processlist | 0 |
| Com_show_profile | 0 |
| Com_show_profiles | 0 |
| Com_show_relaylog_events | 0 |
| Com_show_slave_hosts | 0 |
| Com_show_slave_status | 0 |
| Com_show_status | 2 |
| Com_show_storage_engines | 0 |
| Com_show_table_status | 0 |
| Com_show_tables | 0 |
| Com_show_triggers | 0 |
| Com_show_variables | 0 |
| Com_show_warnings | 0 |
| Com_shutdown | 0 |
| Com_signal | 0 |
| Com_start_all_slaves | 0 |
| Com_start_slave | 0 |
| Com_stmt_close | 0 |
| Com_stmt_execute | 0 |
| Com_stmt_fetch | 0 |
| Com_stmt_prepare | 0 |
| Com_stmt_reprepare | 0 |
| Com_stmt_reset | 0 |
| Com_stmt_send_long_data | 0 |
| Com_stop_all_slaves | 0 |
| Com_stop_slave | 0 |
| Com_truncate | 0 |
| Com_uninstall_plugin | 0 |
| Com_unlock_tables | 0 |
| Com_update | 0 |
| Com_update_multi | 0 |
| Com_xa_commit | 0 |
| Com_xa_end | 0 |
| Com_xa_prepare | 0 |
| Com_xa_recover | 0 |
| Com_xa_rollback | 0 |
| Com_xa_start | 0 |
| Compression | OFF |
| Connection_errors_accept | 0 |
| Connection_errors_internal | 0 |
| Connection_errors_max_connections | 0 |
| Connection_errors_peer_address | 0 |
| Connection_errors_select | 0 |
| Connection_errors_tcpwrap | 0 |
| Connections | 4 |
| Cpu_time | 0.000000 |
| Created_tmp_disk_tables | 0 |
| Created_tmp_files | 6 |
| Created_tmp_tables | 2 |
| Delayed_errors | 0 |
| Delayed_insert_threads | 0 |
| Delayed_writes | 0 |
| Delete_scan | 0 |
| Empty_queries | 0 |
| Executed_events | 0 |
| Executed_triggers | 0 |
| Feature_delay_key_write | 0 |
| Feature_dynamic_columns | 0 |
| Feature_fulltext | 0 |
| Feature_gis | 0 |
| Feature_locale | 0 |
| Feature_subquery | 0 |
| Feature_timezone | 0 |
| Feature_trigger | 0 |
| Feature_xml | 0 |
| Flush_commands | 1 |
| Handler_commit | 1 |
| Handler_delete | 0 |
| Handler_discover | 0 |
| Handler_external_lock | 0 |
| Handler_icp_attempts | 0 |
| Handler_icp_match | 0 |
| Handler_mrr_init | 0 |
| Handler_mrr_key_refills | 0 |
| Handler_mrr_rowid_refills | 0 |
| Handler_prepare | 0 |
| Handler_read_first | 3 |
| Handler_read_key | 0 |
| Handler_read_last | 0 |
| Handler_read_next | 0 |
| Handler_read_prev | 0 |
| Handler_read_retry | 0 |
| Handler_read_rnd | 0 |
| Handler_read_rnd_deleted | 0 |
| Handler_read_rnd_next | 537 |
| Handler_rollback | 0 |
| Handler_savepoint | 0 |
| Handler_savepoint_rollback | 0 |
| Handler_tmp_update | 0 |
| Handler_tmp_write | 516 |
| Handler_update | 0 |
| Handler_write | 0 |
| Innodb_available_undo_logs | 128 |
| Innodb_background_log_sync | 222 |
| Innodb_buffer_pool_bytes_data | 2523136 |
| Innodb_buffer_pool_bytes_dirty | 0 |
| Innodb_buffer_pool_dump_status | Dumping buffer pool(s)
not yet started |
| Innodb_buffer_pool_load_status | L+ oading buffer pool(s)
not yet started |
| Innodb_buffer_pool_pages_data | 154 |
| Innodb_buffer_pool_pages_dirty | 0 |
| Innodb_buffer_pool_pages_flushed | 1 |
| Innodb_buffer_pool_pages_free | 8037 |
| Innodb_buffer_pool_pages_lru_flushed | 0 |
| Innodb_buffer_pool_pages_made_not_young | 0 |
| Innodb_buffer_pool_pages_made_young | 0 |
| Innodb_buffer_pool_pages_misc | 0 |
| Innodb_buffer_pool_pages_old | 0 |
| Innodb_buffer_pool_pages_total | 8191 |
| Innodb_buffer_pool_read_ahead | 0 |
| Innodb_buffer_pool_read_ahead_evicted | 0 |
| Innodb_buffer_pool_read_ahead_rnd | 0 |
| Innodb_buffer_pool_read_requests | 558 |
| Innodb_buffer_pool_reads | 155 |
| Innodb_buffer_pool_wait_free | 0 |
| Innodb_buffer_pool_write_requests | 1 |
| Innodb_checkpoint_age | 0 |
| Innodb_checkpoint_max_age | 80826164 |
| Innodb_data_fsyncs | 5 |
| Innodb_data_pending_fsyncs | 0 |
| Innodb_data_pending_reads | 0 |
| Innodb_data_pending_writes | 0 |
| Innodb_data_read | 2609664 |
| Innodb_data_reads | 172 |
| Innodb_data_writes | 5 |
| Innodb_data_written | 34304 |
| Innodb_dblwr_pages_written | 1 |
| Innodb_dblwr_writes | 1 |
| Innodb_deadlocks | 0 |
| Innodb_have_atomic_builtins | ON |
| Innodb_history_list_length | 0 |
| Innodb_ibuf_discarded_delete_marks | 0 |
| Innodb_ibuf_discarded_deletes | 0 |
| Innodb_ibuf_discarded_inserts | 0 |
| Innodb_ibuf_free_list | 0 |
| Innodb_ibuf_merged_delete_marks | 0 |
| Innodb_ibuf_merged_deletes | 0 |
| Innodb_ibuf_merged_inserts | 0 |
| Innodb_ibuf_merges | 0 |
| Innodb_ibuf_segment_size | 2 |
| Innodb_ibuf_size | 1 |
| Innodb_log_waits | 0 |
| Innodb_log_write_requests | 0 |
| Innodb_log_writes | 1 |
| Innodb_lsn_current | 1616829 |
| Innodb_lsn_flushed | 1616829 |
| Innodb_lsn_last_checkpoint | 1616829 |
| Innodb_master_thread_active_loops | 0 |
| Innodb_master_thread_idle_loops | 222 |
| Innodb_max_trx_id | 2308 |
| Innodb_mem_adaptive_hash | 2217568 |
| Innodb_mem_dictionary | 630703 |
| Innodb_mem_total | 140771328 |
| Innodb_mutex_os_waits | 1 |
| Innodb_mutex_spin_rounds | 30 |
| Innodb_mutex_spin_waits | 1 |
| Innodb_oldest_view_low_limit_trx_id | 0 |
| Innodb_os_log_fsyncs | 3 |
| Innodb_os_log_pending_fsyncs | 0 |
| Innodb_os_log_pending_writes | 0 |
| Innodb_os_log_written | 512 |
| Innodb_page_size | 16384 |
| Innodb_pages_created | 0 |
| Innodb_pages_read | 154 |
| Innodb_pages_written | 1 |
| Innodb_purge_trx_id | 0 |
| Innodb_purge_undo_no | 0 |
| Innodb_read_views_memory | 88 |
| Innodb_row_lock_current_waits | 0 |
| Innodb_row_lock_time | 0 |
| Innodb_row_lock_time_avg | 0 |
| Innodb_row_lock_time_max | 0 |
| Innodb_row_lock_waits | 0 |
| Innodb_rows_deleted | 0 |
| Innodb_rows_inserted | 0 |
| Innodb_rows_read | 0 |
| Innodb_rows_updated | 0 |
| Innodb_system_rows_deleted | 0 |
| Innodb_system_rows_inserted | 0 |
| Innodb_system_rows_read | 0 |
| Innodb_system_rows_updated | 0 |
| Innodb_s_lock_os_waits | 2 |
| Innodb_s_lock_spin_rounds | 60 |
| Innodb_s_lock_spin_waits | 2 |
| Innodb_truncated_status_writes | 0 |
| Innodb_x_lock_os_waits | 0 |
| Innodb_x_lock_spin_rounds | 0 |
| Innodb_x_lock_spin_waits | 0 |
| Innodb_page_compression_saved | 0 |
| Innodb_page_compression_trim_sect512 | 0 |
| Innodb_page_compression_trim_sect1024 | 0 |
| Innodb_page_compression_trim_sect2048 | 0 |
| Innodb_page_compression_trim_sect4096 | 0 |
| Innodb_page_compression_trim_sect8192 | 0 |
| Innodb_page_compression_trim_sect16384 | 0 |
| Innodb_page_compression_trim_sect32768 | 0 |
| Innodb_num_index_pages_written | 0 |
| Innodb_num_non_index_pages_written | 5 |
| Innodb_num_pages_page_compressed | 0 |
| Innodb_num_page_compressed_trim_op | 0 |
| Innodb_num_page_compressed_trim_op_saved | 0 |
| Innodb_num_pages_page_decompressed | 0 |
| Innodb_num_pages_page_compression_error | 0 |
| Innodb_num_pages_encrypted | 0 |
| Innodb_num_pages_decrypted | 0 |
| Innodb_have_lz4 | OFF |
| Innodb_have_lzo | OFF |
| Innodb_have_lzma | OFF |
| Innodb_have_bzip2 | OFF |
| Innodb_have_snappy | OFF |
| Innodb_defragment_compression_failures | 0 |
| Innodb_defragment_failures | 0 |
| Innodb_defragment_count | 0 |
| Innodb_onlineddl_rowlog_rows | 0 |
| Innodb_onlineddl_rowlog_pct_used | 0 |
| Innodb_onlineddl_pct_progress | 0 |
| Innodb_secondary_index_triggered_cluster_reads | 0 |
| Innodb_secondary_index_triggered_cluster_reads_avoided | 0
|
| Innodb_encryption_rotation_pages_read_from_cache | 0 |
| Innodb_encryption_rotation_pages_read_from_disk | 0 |
| Innodb_encryption_rotation_pages_modified | 0 |
| Innodb_encryption_rotation_pages_flushed | 0 |
| Innodb_encryption_rotation_estimated_iops | 0 |
| Innodb_scrub_background_page_reorganizations | 0 |
| Innodb_scrub_background_page_splits | 0 |
| Innodb_scrub_background_page_split_failures_underflow | 0
|
|
Innodb_scrub_background_page_split_failures_out_of_filespace
| 0 |
| Innodb_scrub_background_page_split_failures_missing_index
| 0 |
| Innodb_scrub_background_page_split_failures_unknown | 0 |
| Key_blocks_not_flushed | 0 |
| Key_blocks_unused | 107163 |
| Key_blocks_used | 0 |
| Key_blocks_warm | 0 |
| Key_read_requests | 0 |
| Key_reads | 0 |
| Key_write_requests | 0 |
| Key_writes | 0 |
| Last_query_cost | 0.000000 |
| Master_gtid_wait_count | 0 |
| Master_gtid_wait_time | 0 |
| Master_gtid_wait_timeouts | 0 |
| Max_statement_time_exceeded | 0 |
| Max_used_connections | 1 |
| Memory_used | 273614696 |
| Not_flushed_delayed_rows | 0 |
| Open_files | 25 |
| Open_streams | 0 |
| Open_table_definitions | 18 |
| Open_tables | 11 |
| Opened_files | 77 |
| Opened_plugin_libraries | 0 |
| Opened_table_definitions | 18 |
| Opened_tables | 18 |
| Opened_views | 0 |
| Performance_schema_accounts_lost | 0 |
| Performance_schema_cond_classes_lost | 0 |
| Performance_schema_cond_instances_lost | 0 |
| Performance_schema_digest_lost | 0 |
| Performance_schema_file_classes_lost | 0 |
| Performance_schema_file_handles_lost | 0 |
| Performance_schema_file_instances_lost | 0 |
| Performance_schema_hosts_lost | 0 |
| Performance_schema_locker_lost | 0 |
| Performance_schema_mutex_classes_lost | 0 |
| Performance_schema_mutex_instances_lost | 0 |
| Performance_schema_rwlock_classes_lost | 0 |
| Performance_schema_rwlock_instances_lost | 0 |
| Performance_schema_session_connect_attrs_lost | 0 |
| Performance_schema_socket_classes_lost | 0 |
| Performance_schema_socket_instances_lost | 0 |
| Performance_schema_stage_classes_lost | 0 |
| Performance_schema_statement_classes_lost | 0 |
| Performance_schema_table_handles_lost | 0 |
| Performance_schema_table_instances_lost | 0 |
| Performance_schema_thread_classes_lost | 0 |
| Performance_schema_thread_instances_lost | 0 |
| Performance_schema_users_lost | 0 |
| Prepared_stmt_count | 0 |
| Qcache_free_blocks | 1 |
| Qcache_free_memory | 1031336 |
| Qcache_hits | 0 |
| Qcache_inserts | 0 |
| Qcache_lowmem_prunes | 0 |
| Qcache_not_cached | 0 |
| Qcache_queries_in_cache | 0 |
| Qcache_total_blocks | 1 |
| Queries | 4 |
| Questions | 4 |
| Rows_read | 10 |
| Rows_sent | 517 |
| Rows_tmp_read | 516 |
| Rpl_status | AUTH_MASTER |
| Select_full_join | 0 |
| Select_full_range_join | 0 |
| Select_range | 0 |
| Select_range_check | 0 |
| Select_scan | 2 |
| Slave_connections | 0 |
| Slave_heartbeat_period | 0.000 |
| Slave_open_temp_tables | 0 |
| Slave_received_heartbeats | 0 |
| Slave_retried_transactions | 0 |
| Slave_running | OFF |
| Slave_skipped_errors | 0 |
| Slaves_connected | 0 |
| Slaves_running | 0 |
| Slow_launch_threads | 0 |
| Slow_queries | 0 |
| Sort_merge_passes | 0 |
| Sort_priority_queue_sorts | 0 |
| Sort_range | 0 |
| Sort_rows | 0 |
| Sort_scan | 0 |
| Ssl_accept_renegotiates | 0 |
| Ssl_accepts | 0 |
| Ssl_callback_cache_hits | 0 |
| Ssl_cipher | |
| Ssl_cipher_list | |
| Ssl_client_connects | 0 |
| Ssl_connect_renegotiates | 0 |
| Ssl_ctx_verify_depth | 0 |
| Ssl_ctx_verify_mode | 0 |
| Ssl_default_timeout | 0 |
| Ssl_finished_accepts | 0 |
| Ssl_finished_connects | 0 |
| Ssl_server_not_after | |
| Ssl_server_not_before | |
| Ssl_session_cache_hits | 0 |
| Ssl_session_cache_misses | 0 |
| Ssl_session_cache_mode | NONE |
| Ssl_session_cache_overflows | 0 |
| Ssl_session_cache_size | 0 |
| Ssl_session_cache_timeouts | 0 |
| Ssl_se�ˇ� � � /& SHOW TABLESSyntax
------
SHOW [FULL] TABLES [FROM db_name]
[LIKE 'pattern' | WHERE expr]
Description
-----------
SHOW TABLES lists the non-TEMPORARY tables, sequences and
views in a given database.
The LIKE clause, if present on its own, indicates which
table names to match. The WHERE and LIKE clauses can be
given to select rows using more general conditions, as
discussed in Extended SHOW. For example, when searching for
tables in the test database, the column name for use in the
WHERE and LIKE clauses will be Tables_in_test
The FULL modifier is supported such that SHOW FULL TABLES
displays a second output column. Values for the second
column. Table_type, are BASE TABLE for a table, VIEW for a
view and SEQUENCE for a sequence.
You can also get this information using:
mysqlshow db_name
See mysqlshow for more details.
If you have no privileges for a base table or view, it does
not show up in the output from SHOW TABLES or mysqlshow
db_name.
The information_schema.TABLES table, as well as the SHOW
TABLE STATUS statement, provide extended information about
tables.
Examples
--------
SHOW TABLES;
+----------------------+
| Tables_in_test |
+----------------------+
| animal_count |
| animals |
| are_the_mooses_loose |
| aria_test2 |
| t1 |
| view1 |
+----------------------+
Showing the tables beginning with a only.
SHOW TABLES WHERE Tables_in_test LIKE 'a%';
+----------------------+
| Tables_in_test |
+----------------------+
| animal_count |
| animals |
| are_the_mooses_loose |
| aria_test2 |
+----------------------+
Showing tables and table types:
SHOW FULL TABLES;
+----------------+------------+
| Tables_in_test | Table_type |
+----------------+------------+
| s1 | SEQUENCE |
| student | BASE TABLE |
| v1 | VIEW |
+----------------+------------+
URL: https://mariadb.com/kb/en/show-tables/https://mariadb.com/kb/en/show-tables/ � v0 SHOW TABLE_STATISTICSMariaDB 5.2 introduced the User Statistics feature.
Syntax
------
SHOW TABLE_STATISTICS
Description
-----------
The SHOW TABLE_STATISTICS statement was introduced in
MariaDB 5.2 as part of the User Statistics feature. It was
removed as a separate statement in MariaDB 10.1.1, but
effectively replaced by the generic SHOW
information_schema_table statement. The
information_schema.TABLE_STATISTICS table shows statistics
on table usage
The userstat system variable must be set to 1 to activate
this feature. See the User Statistics and
information_schema.TABLE_STATISTICS articles for more
information.
Example
From MariaDB 10.0
SHOW TABLE_STATISTICS\G
*************************** 1. row
***************************
Table_schema: mysql
Table_name: proxies_priv
Rows_read: 2
Rows_changed: 0
Rows_changed_x_#indexes: 0
*************************** 2. row
***************************
Table_schema: test
Table_name: employees_example
Rows_read: 7
Rows_changed: 0
Rows_changed_x_#indexes: 0
*************************** 3. row
***************************
Table_schema: mysql
Table_name: user
Rows_read: 16
Rows_changed: 0
Rows_changed_x_#indexes: 0
*************************** 4. row
***************************
Table_schema: mysql
Table_name: db
Rows_read: 2
Rows_changed: 0
Rows_changed_x_#indexes: 0
URL: https://mariadb.com/kb/en/show-table-statistics/https://mariadb.com/kb/en/show-table-statistics/ �
Z ( SHOW TRIGGERSSyntax
------
SHOW TRIGGERS [FROM db_name]
[LIKE 'pattern' | WHERE expr]
Description
-----------
SHOW TRIGGERS lists the triggers currently defined for
tables in a database (the default database unless a FROM
clause is given). This statement requires the
TRIGGER privilege (prior to MySQL
5.1.22, it required the SUPER privilege).
The LIKE clause, if present on its own, indicates which
table names to
match and causes the statement to display triggers for those
tables. The WHERE and LIKE clauses can be given to select
rows using more general conditions, as discussed in Extended
SHOW.
Similar information is stored in the
information_schema.TRIGGERS table.
If there are multiple triggers for the same action, then the
triggers are shown in action order.
Examples
--------
For the trigger defined at Trigger Overview:
SHOW triggers Like 'animals' \G
*************************** 1. row
***************************
Trigger: the_mooses_are_loose
Event: INSERT
Table: animals
Statement: BEGIN
IF NEW.name = 'Moose' THEN
UPDATE animal_count SET animal_count.animals =
animal_count.animals+100;
ELSE
UPDATE animal_count SET animal_count.animals =
animal_count.animals+1;
END IF;
END
Timing: AFTER
Created: 2016-09-29 13:53:34.35
sql_mode:
Definer: root@localhost
character_set_client: utf8
collation_connection: utf8_general_ci
Database Collation: latin1_swedish_ci
Listing all triggers associated with a certain table:
SHOW TRIGGERS FROM test WHERE `Table` = 'user' \G
*************************** 1. row
***************************
Trigger: user_ai
Event: INSERT
Table: user
Statement: BEGIN END
Timing: AFTER
Created: 2016-09-29 13:53:34.35
sql_mode:
Definer: root@%
character_set_client: utf8
collation_connection: utf8_general_ci
Database Collation: latin1_swedish_ci
SHOW triggers WHERE Event Like 'Insert' \G
*************************** 1. row
***************************
Trigger: the_mooses_are_loose
Event: INSERT
Table: animals
Statement: BEGIN
IF NEW.name = 'Moose' THEN
UPDATE animal_count SET animal_count.animals =
animal_count.animals+100;
ELSE
UPDATE animal_count SET animal_count.animals =
animal_count.animals+1;
END IF;
END
Timing: AFTER
Created: 2016-09-29 13:53:34.35
sql_mode:
Definer: root@localhost
character_set_client: utf8
collation_connection: utf8_general_ci
Database Collation: latin1_swedish_ci
character_set_client is the session value of the
character_set_client system variable when the trigger was
created.
collation_connection is the session value of the
collation_connection system variable when the trigger was
created.
Database Collation is the collation of the database
with which the trigger is associated.
These columns were added in MariaDB/MySQL 5.1.21.
Old triggers created before MySQL 5.7 and MariaDB 10.2.3 has
NULL in the Created column.
URL: https://mariadb.com/kb/en/show-triggers/https://mariadb.com/kb/en/show-triggers/ C
� z� n�l� �� � �/ SHOW USER_STATISTICSMariaDB 5.2 introduced the User Statistics feature.
Syntax
------
SHOW USER_STATISTICS
Description
-----------
The SHOW USER_STATISTICS statement was introduced in MariaDB
5.2 as part of the User Statistics feature. It was removed
as a separate statement in MariaDB 10.1.1, but effectively
replaced by the generic SHOW information_schema_table
statement. The information_schema.USER_STATISTICS table
holds statistics about user activity. You can use this table
to find out such things as which user is causing the most
load and which users are being abusive. You can also use
this table to measure how close to capacity the server may
be.
The userstat system variable must be set to 1 to activate
this feature. See the User Statistics and
information_schema.USER_STATISTICS table for more
information.
Example
From MariaDB 10.0:
SHOW USER_STATISTICS\G
*************************** 1. row
***************************
User: root
Total_connections: 1
Concurrent_connections: 0
Connected_time: 3297
Busy_time: 0.14113400000000006
Cpu_time: 0.017637000000000003
Bytes_received: 969
Bytes_sent: 22355
Binlog_bytes_written: 0
Rows_read: 10
Rows_sent: 67
Rows_deleted: 0
Rows_inserted: 0
Rows_updated: 0
Select_commands: 7
Update_commands: 0
Other_commands: 0
Commit_transactions: 1
Rollback_transactions: 0
Denied_connections: 0
Lost_connections: 0
Access_denied: 0
Empty_queries: 7
URL: https://mariadb.com/kb/en/show-user-statistics/https://mariadb.com/kb/en/show-user-statistics/ � �) SHOW VARIABLESSyntax
------
SHOW [GLOBAL | SESSION] VARIABLES
[LIKE 'pattern' | WHERE expr]
Description
-----------
SHOW VARIABLES shows the values of MariaDB system variables.
This
information also can be obtained using the mysqladmin
variables
command. The LIKE clause, if present, indicates which
variable names
to match. The WHERE clause can be given to select rows using
more
general conditions.
With the GLOBAL modifier, SHOW VARIABLES displays the values
that are
used for new connections to MariaDB. With SESSION, it
displays the
values that are in effect for the current connection. If no
modifier
is present, the default is SESSION. LOCAL is a synonym for
SESSION.
With a LIKE clause, the statement displays only rows for
those
variables with names that match the pattern. To obtain the
row for a
specific variable, use a LIKE clause as shown:
SHOW VARIABLES LIKE 'maria_group_commit';
SHOW SESSION VARIABLES LIKE 'maria_group_commit';
To get a list of variables whose name match a pattern, use
the "%"
wildcard character in a LIKE clause:
SHOW VARIABLES LIKE '%maria%';
SHOW GLOBAL VARIABLES LIKE '%maria%';
Wildcard characters can be used in any position within the
pattern to
be matched. Strictly speaking, because "_" is a wildcard
that matches
any single character, you should escape it as "\_" to
match it
literally. In practice, this is rarely necessary.
The WHERE and LIKE clauses can be given to select rows using
more general conditions, as discussed in Extended SHOW.
See SET for information on setting server system variables.
See Server System Variables for a list of all the variables
that can be set.
You can also see the server variables by querying the
Information Schema GLOBAL_VARIABLES and SESSION_VARIABLES
tables.
Examples
--------
SHOW VARIABLES LIKE 'aria%';
+------------------------------------------+---------------------+
| Variable_name | Value |
+------------------------------------------+---------------------+
| aria_block_size | 8192 |
| aria_checkpoint_interval | 30 |
| aria_checkpoint_log_activity | 1048576 |
| aria_force_start_after_recovery_failures | 0 |
| aria_group_commit | none |
| aria_group_commit_interval | 0 |
| aria_log_file_size | 1073741824 |
| aria_log_purge_type | immediate |
| aria_max_sort_file_size | 9223372036853727232 |
| aria_page_checksum | ON |
| aria_pagecache_age_threshold | 300 |
| aria_pagecache_buffer_size | 134217728 |
| aria_pagecache_division_limit | 100 |
| aria_recover | NORMAL |
| aria_repair_threads | 1 |
| aria_sort_buffer_size | 134217728 |
| aria_stats_method | nulls_unequal |
| aria_sync_log_dir | NEWFILE |
| aria_used_for_temp_tables | ON |
+------------------------------------------+---------------------+
SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM
INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE
VARIABLE_NAME LIKE 'max_error_count' OR
VARIABLE_NAME LIKE 'innodb_sync_spin_loops';
+---------------------------+---------------+--------------+
| VARIABLE_NAME | SESSION_VALUE | GLOBAL_VALUE |
+---------------------------+---------------+--------------+
| MAX_ERROR_COUNT | 64 | 64 |
| INNODB_SYNC_SPIN_LOOPS | NULL | 30 |
+---------------------------+---------------+--------------+
SET GLOBAL max_error_count=128;
SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE FROM
INFORMATION_SCHEMA.SYSTEM_VARIABLES WHERE
VARIABLE_NAME LIKE 'max_error_count' OR
VARIABLE_NAME LIKE 'innodb_sync_spin_loops';
+---------------------------+---------------+--------------+
| VARIABLE_NAME | SESSION_VALUE | GLOBAL_VALUE |
+---------------------------+---------------+--------------+
| MAX_ERROR_COUNT | 64 | 128 |
| INNODB_SYNC_SPIN_LOOPS | NULL | 30 |
+---------------------------+---------------+--------------+
SET GLOBAL max_error_count=128;
SHOW VARIABLES LIKE 'max_error_count';
+-----------------+-------+
| Variable_name | Value |
+-----------------+-------+
| max_error_count | 64 |
+-----------------+-------+
SHOW GLOBAL VARIABLES LIKE 'max_error_count';
+-----------------+-------+
| Variable_name | Value |
+-----------------+-------+
| max_error_count | 128 |
+-----------------+-------+
Because the following variable only has a global scope, the
global value is returned even when specifying SESSION (in
this case by default):
SHOW VARIABLES LIKE 'innodb_sync_spin_loops';
+------------------------+-------+
| Variable_name | Value |
+------------------------+-------+
| innodb_sync_spin_loops | 30 |
+------------------------+-------+
URL: https://mariadb.com/kb/en/show-variables/https://mariadb.com/kb/en/show-variables/ & �� � �
�
�
( SHOW WARNINGSSyntax
------
SHOW WARNINGS [LIMIT [offset,] row_count]
SHOW ERRORS [LIMIT row_count OFFSET offset]
SHOW COUNT(*) WARNINGS
Description
-----------
SHOW WARNINGS shows the error, warning, and note messages
that resulted from the last statement that generated
messages in the
current session. It shows nothing if the last statement used
a table
and generated no messages. (That is, a statement that uses a
table but
generates no messages clears the message list.) Statements
that do not
use tables and do not generate messages have no effect on
the message
list.
A note is different to a warning in that it only appears if
the sql_notes variable is set to 1 (the default), and is not
converted to an error if strict mode is enabled.
A related statement, SHOW ERRORS, shows only the errors.
The SHOW COUNT(*) WARNINGS statement displays the total
number of errors, warnings, and notes. You can also retrieve
this number from
the warning_count variable:
SHOW COUNT(*) WARNINGS;
SELECT @@warning_count;
The value of warning_count might be greater than the number
of messages displayed by SHOW WARNINGS if the
max_error_count system variable is set so low that not all
messages are stored.
The LIMIT clause has the same syntax as for the
SELECT statement.
SHOW WARNINGS can be used after EXPLAIN EXTENDED to see how
a query is internally rewritten by MariaDB.
If the sql_notes server variable is set to 1, Notes are
included in the output of SHOW WARNINGS; if it is set to 0,
this statement will not show (or count) Notes.
The results of SHOW WARNINGS and SHOW COUNT(*) WARNINGS are
directly sent to the client. If you need to access those
information in a stored program, you can use the GET
DIAGNOSTICS statement instead.
For a list of MariaDB error codes, see MariaDB Error Codes.
The mysql client also has a number of options related to
warnings. The \W command will show warnings after every
statement, while \w will disable this. Starting the client
with the --show-warnings option will show warnings after
every statement.
MariaDB 10.3.1 implements a stored routine error stack
trace. SHOW WARNINGS can also be used to show more
information. See the example below.
Examples
--------
SELECT 1/0;
+------+
| 1/0 |
+------+
| NULL |
+------+
SHOW COUNT(*) WARNINGS;
+-------------------------+
| @@session.warning_count |
+-------------------------+
| 1 |
+-------------------------+
SHOW WARNINGS;
+---------+------+---------------+
| Level | Code | Message |
+---------+------+---------------+
| Warning | 1365 | Division by 0 |
+---------+------+---------------+
Stack Trace
From MariaDB 10.3.1, displaying a stack trace:
DELIMITER $$
CREATE OR REPLACE PROCEDURE p1()
BEGIN
DECLARE c CURSOR FOR SELECT * FROM not_existing;
OPEN c;
CLOSE c;
END;
$$
CREATE OR REPLACE PROCEDURE p2()
BEGIN
CALL p1;
END;
$$
DELIMITER ;
CALL p2;
ERROR 1146 (42S02): Table 'test.not_existing' doesn't
exist
SHOW WARNINGS;
+-------+------+-----------------------------------------+
| Level | Code | Message |
+-------+------+-----------------------------------------+
| Error | 1146 | Table 'test.not_existing' doesn't exist
|
| Note | 4091 | At line 6 in test.p1 |
| Note | 4091 | At line 4 in test.p2 |
+-------+------+-----------------------------------------+
SHOW WARNINGS displays a stack trace, showing where the
error actually happened:
Line 4 in test.p1 is the OPEN command which actually raised
the error
Line 3 in test.p2 is the CALL statement, calling p1 from p2.
URL: https://mariadb.com/kb/en/show-warnings/https://mariadb.com/kb/en/show-warnings/ � �0 SHOW WSREP_MEMBERSHIPMariaDB 10.1.2
SHOW WSREP_MEMBERSHIP was introduced with the WSREP_INFO
plugin in MariaDB 10.1.2.
Syntax
------
SHOW WSREP_MEMBERSHIP
Description
-----------
The SHOW WSREP_MEMBERSHIP statement returns Galera node
cluster membership information. It returns the same
information as found in the
information_schema.WSREP_MEMBERSHIP table. Only users with
the SUPER privilege can access this information.
Examples
--------
SHOW WSREP_MEMBERSHIP;
+-------+--------------------------------------+----------+-----------------+
| Index | Uuid | Name | Address |
+-------+--------------------------------------+----------+-----------------+
| 0 | 19058073-8940-11e4-8570-16af7bf8fced | my_node1 |
10.0.2.15:16001 |
| 1 | 19f2b0e0-8942-11e4-9cb8-b39e8ee0b5dd | my_node3 |
10.0.2.15:16003 |
| 2 | d85e62db-8941-11e4-b1ef-4bc9980e476d | my_node2 |
10.0.2.15:16002 |
+-------+--------------------------------------+----------+-----------------+
URL: https://mariadb.com/kb/en/show-wsrep_membership/https://mariadb.com/kb/en/show-wsrep_membership/ � , SHOW WSREP_STATUSMariaDB 10.1.2
SHOW WSREP_STATUS was introduced with the WSREP_INFO plugin
in MariaDB 10.1.2.
Syntax
------
SHOW WSREP_STATUS
Description
-----------
The SHOW WSREP_STATUS statement returns Galera node and
cluster status information. It returns the same information
as found in the information_schema.WSREP_STATUS table. Only
users with the SUPER privilege can access this information.
Examples
--------
SHOW WSREP_STATUS;
+------------+-------------+----------------+--------------+
| Node_Index | Node_Status | Cluster_Status | Cluster_Size |
+------------+-------------+----------------+--------------+
| 0 | Synced | Primary | 3 |
+------------+-------------+----------------+--------------+
URL: https://mariadb.com/kb/en/show-wsrep_status/https://mariadb.com/kb/en/show-wsrep_status/ Q5J )�f� �h � v CALLSyntax
------
CALL sp_name([parameter[,...]])
CALL sp_name[()]
Description
-----------
The CALL statement invokes a stored procedure that was
defined previously with CREATE PROCEDURE.
Stored procedure names can be specified as
database_name.procedure_name. Procedure names and database
names can be quoted with backticks (). This is necessary if
they are reserved words, or contain special characters. See
identifier qualifiers for details.
Before MySQL 5.1.13, stored procedures that take no
arguments required parentheses. In current releases of
MariaDB, CALL p() and CALL p are equivalent.
If parentheses are used, any number of spaces, tab
characters and new line characters is allowed between the
procedure's name and the open parenthesis.
CALL can pass back values to its caller using parameters
that are declared as OUT or INOUT
parameters. If no value is assigned to an OUT parameter,
NULL is assigned (and its former value is lost). To pass
such values from another stored program you can use
user-defined variables, local variables or routine's
parameters; in other contexts, you can only use user-defined
variables.
CALL can also be executed as a prepared statement.
Placeholders can be used for IN parameters in all versions
of MariaDB; for OUT and INOUT parameters, placeholders can
be used since MariaDB 5.5.
When the procedure returns, a client program can also obtain
the
number of rows affected for the final statement executed
within the routine: At
the SQL level, call the ROW_COUNT() function; from the C
API, call the mysql_affected_rows() function.
If the CLIENT_MULTI_RESULTS API flag is set, CALL can return
any number of resultsets and the called stored procedure can
execute prepared statements. If it is not set, at most one
resultset can be returned and prepared statements cannot be
used within procedures.
URL: https://mariadb.com/kb/en/call/https://mariadb.com/kb/en/call/ � - Concurrent InsertsThe MyISAM storage engine supports concurrent inserts. This
feature allows SELECT statements to be executed during
INSERT operations, reducing contention.
Whether concurrent inserts can be used or not depends on the
value of the concurrent_insert server system variable:
NEVER (0) disables concurrent inserts.
AUTO (1) allows concurrent inserts only when the target
table has no free blocks (no data in the middle of the table
has been deleted after the last OPTIMIZE TABLE). This is the
default.
ALWAYS (2) always enables concurrent inserts.
If the binary log is used, CREATE TABLE ... SELECT and
INSERT ... SELECT statements cannot use concurrent inserts.
These statements acquire a read lock on the table, so
concurrent inserts will need to wait. This way the log can
be safely used to restore data.
Concurrent inserts is not used by slaves with the row based
replication (see binary log formats).
If an INSERT statement contain the HIGH_PRIORITY clause,
concurrent inserts cannot be used. INSERT ... DELAYED is
usually unneeded if concurrent inserts are enabled.
LOAD DATA INFILE uses concurrent inserts if the CONCURRENT
keyword is specified and concurrent_insert is not NEVER.
This makes the statement slower (even if no other sessions
access the table) but reduces contention.
LOCK TABLES allows non-conflicting concurrent inserts if a
READ LOCAL lock is used. Concurrent inserts are not allowed
if the LOCAL keyword is omitted.
Notes
The decision to enable concurrent insert for a table is done
when the table is opened. If you change the value of
concurrent_insert it will only affect new opened tables. If
you want it to work for also for tables in use or cached,
you should do FLUSH TABLES after setting the variable.
URL: https://mariadb.com/kb/en/concurrent-inserts/https://mariadb.com/kb/en/concurrent-inserts/ � L ! EXCEPTEXCEPT was introduced in MariaDB 10.3.0.
The result of EXCEPT is all records of the left SELECT
result set except records which are in right SELECT result
set, i.e. it is subtraction of two result sets.
Syntax
------
SELECT ...
(INTERSECT | EXCEPT | UNION [ALL | DISTINCT]) SELECT ...
[(INTERSECT | EXCEPT | UNION [ALL | DISTINCT]) SELECT ...]
[ORDER BY [column [, column ...]]]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]
Please note:
ALL is not supported by EXCEPT (and it is difficult to make
sense of ALL with EXCEPT).
Brackets for explicit operation precedence are not
supported; use a subquery in the FROM clause as a
workaround).
Description
-----------
MariaDB has supported EXCEPT and INTERSECT in addition to
UNION since MariaDB 10.3.
All behavior for naming columns, ORDER BY and LIMIT is the
same as for UNION.
EXCEPT implicitly supposes a DISTINCT operation.
The result of EXCEPT is all records of the left SELECT
result except records which are in right SELECT result set,
i.e. it is subtraction of two result sets.
EXCEPT and UNION have the same operation precedence.
Parentheses
From MariaDB 10.4.0, parentheses can be used to specify
precedence. Before this, a syntax error would be returned.
Examples
--------
Show customers which are not employees:
(SELECT e_name AS name, email FROM customers)
EXCEPT
(SELECT c_name AS name, email FROM employees);
Difference between UNION, EXCEPT and INTERSECT:
CREATE TABLE seqs (i INT);
INSERT INTO seqs VALUES (1),(2),(3),(4),(5),(6);
SELECT i FROM seqs WHERE i =3;
+------+
| i |
+------+
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
| 6 |
+------+
SELECT i FROM seqs WHERE i =3;
+------+
| i |
+------+
| 1 |
| 2 |
+------+
SELECT i FROM seqs WHERE i =3;
+------+
| i |
+------+
| 3 |
+------+
Parentheses for specifying precedence, from MariaDB 10.4.0
CREATE OR REPLACE TABLE t1 (a INT);
CREATE OR REPLACE TABLE t2 (b INT);
CREATE OR REPLACE TABLE t3 (c INT);
INSERT INTO t1 VALUES (1),(2),(3),(4);
INSERT INTO t2 VALUES (5),(6);
INSERT INTO t3 VALUES (1),(6);
((SELECT a FROM t1) UNION (SELECT b FROM t2)) EXCEPT (SELECT
c FROM t3);
+------+
| a |
+------+
| 2 |
| 3 |
| 4 |
| 5 |
+------+
(SELECT a FROM t1) UNION ((SELECT b FROM t2) EXCEPT (SELECT
c FROM t3));
+------+
| a |
+------+
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
+------+
URL: https://mariadb.com/kb/en/except/https://mariadb.com/kb/en/except/ � �T ��%�j �� � t! DELETESyntax
------
Single-table syntax:
DELETE [LOW_PRIORITY] [QUICK] [IGNORE]
FROM tbl_name [PARTITION (partition_list)]
[WHERE where_condition]
[ORDER BY ...]
[LIMIT row_count]
[RETURNING select_expr
[, select_expr ...]]
Multiple-table syntax:
DELETE [LOW_PRIORITY] [QUICK] [IGNORE]
tbl_name[.*] [, tbl_name[.*]] ...
FROM table_references
[WHERE where_condition]
Or:
DELETE [LOW_PRIORITY] [QUICK] [IGNORE]
FROM tbl_name[.*] [, tbl_name[.*]] ...
USING table_references
[WHERE where_condition]
Trimming history:
DELETE HISTORY
FROM tbl_name [PARTITION (partition_list)]
[BEFORE SYSTEM_TIME [TIMESTAMP|TRANSACTION] expression]
Description
-----------
Option | Description |
LOW_PRIORITY | Wait until all SELECT's are done before
starting the statement. Used with storage engines that uses
table locking (MyISAM, Aria etc). See HIGH_PRIORITY and
LOW_PRIORITY clauses for details. |
QUICK | Signal the storage engine that it should expect that
a lot of rows are deleted. The storage engine engine can do
things to speed up the DELETE like ignoring merging of data
blocks until all rows are deleted from the block (instead of
when a block is half full). This speeds up things at the
expanse of lost space in data blocks. At least MyISAM and
Aria support this feature. |
IGNORE | Don't stop the query even if a not-critical error
occurs (like data overflow). See How IGNORE works for a full
description. |
For the single-table syntax, the DELETE statement deletes
rows
from tbl_name and returns a count of the number of deleted
rows. This count can
be obtained by calling the ROW_COUNT() function. The
WHERE clause, if given, specifies the conditions that
identify
which rows to delete. With no WHERE clause, all rows are
deleted. If the ORDER BY clause is specified, the rows are
deleted in the order that is specified. The LIMIT clause
places a limit on the number of rows that can be deleted.
For the multiple-table syntax, DELETE deletes from each
tbl_name the rows that satisfy the conditions. In this case,
ORDER BY and LIMIT> cannot be used. A DELETE can also
reference tables which are located in different databases;
see Identifier Qualifiers for the syntax.
where_condition is an expression that evaluates to true for
each row to be deleted. It is specified as described in
SELECT.
Currently, you cannot delete from a table and select from
the same
table in a subquery.
You need the DELETE privilege on a table to delete rows from
it. You need only the SELECT privilege for any columns that
are only read, such as those named in the WHERE clause. See
GRANT.
The PARTITION clause was introduced in MariaDB 10.0. See
Partition Pruning and Selection for details.
As stated, a DELETE statement with no WHERE
clause deletes all rows. A faster way to do this, when you
do not need to know
the number of deleted rows, is to use TRUNCATE TABLE.
However,
within a transaction or if you have a lock on the table,
TRUNCATE TABLE cannot be used whereas DELETE
can. See TRUNCATE TABLE, and
LOCK.
From MariaDB 10.0.5, it is possible to return a resultset of
the deleted rows for a single table to the client by using
the syntax DELETE ... RETURNING select_expr [, select_expr2
...]]
Any of SQL expression that can be calculated from a single
row fields is allowed. Subqueries are allowed. The AS
keyword is allowed, so it is possible to use aliases.
The use of aggregate functions is not allowed. RETURNING
cannot be used in multi-table DELETEs.
Same Source and Target Table
Until MariaDB 10.3.1, deleting from a table with the same
source and target was not possible. From MariaDB 10.3.1,
this is now possible. For example:
DELETE FROM t1 WHERE c1 IN (SELECT b.c1 FROM t1 b WHERE
b.c2=0);
One can use DELETE HISTORY to delete historical information
from System-versioned tables.
Examples
--------
How to use the ORDER BY and LIMIT clauses:
DELETE FROM page_hit ORDER BY timestamp LIMIT 1000000;
How to use the RETURNING clause:
DELETE FROM t RETURNING f1;
+------+
| f1 |
+------+
| 5 |
| 50 |
| 500 |
+------+
The following statement joins two tables: one is only used
to satisfy a WHERE condition, but no row is deleted from it;
rows from the other table are deleted, instead.
DELETE post FROM blog INNER JOIN post WHERE blog.id =
post.blog_id;
Deleting from the Same Source and Target
CREATE TABLE t1 (c1 INT, c2 INT);
DELETE FROM t1 WHERE c1 IN (SELECT b.c1 FROM t1 b WHERE
b.c2=0);
Until MariaDB 10.3.1, this returned:
ERROR 1093 (HY000): Table 't1' is specified twice, both as
a target for 'DELETE'
and as a separate source for
From MariaDB 10.3.1:
Query OK, 0 rows affected (0.00 sec)
URL: https://mariadb.com/kb/en/delete/https://mariadb.com/kb/en/delete/ � :9 HIGH_PRIORITY and LOW_PRIORITYThe XtraDB/InnoDB storage engine uses row-level locking to
ensure data integrity. However some storage engines (such as
MEMORY, MyISAM, Aria and MERGE) lock the whole table to
prevent conflicts. These storage engines use two separate
queues to remember pending statements; one is for SELECTs
and the other one is for write statements (INSERT, DELETE,
UPDATE). By default, the latter has a higher priority.
To give write operations a lower priority, the
low_priority_updates server system variable can be set to
ON. The option is available on both the global and session
levels, and it can be set at startup or via the SET
statement.
When too many table locks have been set by write statements,
some pending SELECTs are executed. The maximum number of
write locks that can be acquired before this happens is
determined by the max_write_lock_count server system
variable, which is dynamic.
If write statements have a higher priority (default), the
priority of individual write statements (INSERT, REPLACE,
UPDATE, DELETE) can be changed via the LOW_PRIORITY
attribute, and the priority of a SELECT statement can be
raised via the HIGH_PRIORITY attribute. Also, LOCK TABLES
supports a LOW_PRIORITY attribute for WRITE locks.
If read statements have a higher priority, the priority of
an INSERT can be changed via the HIGH_PRIORITY attribute.
However, the priority of other write statements cannot be
raised individually.
The use of LOW_PRIORITY or HIGH_PRIORITY for an INSERT
prevents Concurrent Inserts from being used.
URL:
https://mariadb.com/kb/en/high_priority-and-low_priority/https://mariadb.com/kb/en/high_priority-and-low_priority/ �� ����� � � b# GROUP BYUse the GROUP BY clause in a SELECT statement to group rows
together that have the same value in one or more column, or
the same computed value using expressions with any
functions and operators except
grouping functions. When you
use a GROUP BY clause, you will get a single result row for
each group of rows
that have the same value for the expression given in GROUP
BY.
When grouping rows, grouping values are compared as if by
the = operator.
For string values, the = operator ignores trailing
whitespace and may normalize
characters and ignore case, depending on the collation in
use.
You can use any of the grouping functions in your select
expression. Their values will
be calculated based on all the rows that have been grouped
together for each result
row. If you select a non-grouped column or a value computed
from a non-grouped
column, it is undefined which row the returned value is
taken from. This is not permitted if the ONLY_FULL_GROUP_BY
SQL_MODE is used.
You can use multiple expressions in the GROUP BY clause,
separated by commas.
Rows are grouped together if they match on each of the
expressions.
You can also use a single integer as the grouping
expression. If you use an integer n,
the results will be grouped by the nth column in the select
expression.
The WHERE clause is applied before the GROUP BY clause. It
filters non-aggregated
rows before the rows are grouped together. To filter grouped
rows based on aggregate values,
use the HAVING clause. The HAVING clause takes any
expression and evaluates it as
a boolean, just like the WHERE clause. You can use grouping
functions in the HAVING
clause. As with the select expression, if you reference
non-grouped columns in the HAVING
clause, the behavior is undefined.
By default, if a GROUP BY clause is present, the rows in the
output will be sorted by the expressions used in the GROUP
BY. You can also specify ASC or DESC (ascending, descending)
after those expressions, like in ORDER BY. The default is
ASC.
If you want the rows to be sorted by another field, you can
add an explicit ORDER BY. If you don't want the result to
be ordered, you can add ORDER BY NULL.
WITH ROLLUP
The WITH ROLLUP modifer adds extra rows to the resultset
that represent super-aggregate summaries. For a full
description with examples, see SELECT WITH ROLLUP.
GROUP BY Examples
Consider the following table that records how many times
each user has played and won a game:
CREATE TABLE plays (name VARCHAR(16), plays INT, wins INT);
INSERT INTO plays VALUES
("John", 20, 5),
("Robert", 22, 8),
("Wanda", 32, 8),
("Susan", 17, 3);
Get a list of win counts along with a count:
SELECT wins, COUNT(*) FROM plays GROUP BY wins;
+------+----------+
| wins | COUNT(*) |
+------+----------+
| 3 | 1 |
| 5 | 1 |
| 8 | 2 |
+------+----------+
3 rows in set (0.00 sec)
The GROUP BY expression can be a computed value, and can
refer back to an identifer
specified with AS. Get a list of win averages along with a
count:
SELECT (wins / plays) AS winavg, COUNT(*) FROM plays GROUP
BY winavg;
+--------+----------+
| winavg | COUNT(*) |
+--------+----------+
| 0.1765 | 1 |
| 0.2500 | 2 |
| 0.3636 | 1 |
+--------+----------+
3 rows in set (0.00 sec)
You can use any grouping function
in the select expression. For each win average as above, get
a list of the average play
count taken to get that average:
SELECT (wins / plays) AS winavg, AVG(plays) FROM plays
GROUP BY winavg;
+--------+------------+
| winavg | AVG(plays) |
+--------+------------+
| 0.1765 | 17.0000 |
| 0.2500 | 26.0000 |
| 0.3636 | 22.0000 |
+--------+------------+
3 rows in set (0.00 sec)
You can filter on aggregate information using the HAVING
clause. The HAVING
clause is applied after GROUP BY and allows you to filter on
aggregate data that is
not available to the WHERE clause. Restrict the above
example to results that involve
an average number of plays over 20:
SELECT (wins / plays) AS winavg, AVG(plays) FROM plays
GROUP BY winavg HAVING AVG(plays) > 20;
+--------+------------+
| winavg | AVG(plays) |
+--------+------------+
| 0.2500 | 26.0000 |
| 0.3636 | 22.0000 |
+--------+------------+
2 rows in set (0.00 sec)
See Also
SELECT
Joins and Subqueries
LIMIT
ORDER BY
Common Table Expressions
SELECT WITH ROLLUP
SELECT INTO OUTFILE
SELECT INTO DUMPFILE
FOR UPDATE
LOCK IN SHARE MODE
Optimizer Hints
URL: https://mariadb.com/kb/en/group-by/https://mariadb.com/kb/en/group-by/ �
! IGNOREThe IGNORE option tells the server to ignore some common
errors.
IGNORE can be used with the following statements:
DELETE
INSERT (see also INSERT IGNORE)
LOAD DATA INFILE
UPDATE
ALTER TABLE
CREATE TABLE ... SELECT
INSERT ... SELECT
The logic used:
Variables out of ranges are replaced with the
maximum/minimum value.
SQL_MODEs STRICT_TRANS_TABLES, STRICT_ALL_TABLES,
NO_ZERO_IN_DATE, NO_ZERO_DATE are ignored.
Inserting NULL in a NOT NULL field will insert 0 ( in a
numerical
field), 0000-00-00 ( in a date field) or an empty string (
in a character
field).
Rows that cause a duplicate key error or break a foreign key
constraint are
not inserted, updated, or deleted.
The following errors are ignored:
Error number | Symbolic error name | Description |
1022 | ER_DUP_KEY | Can't write; duplicate key in table
'%s' |
1048 | ER_BAD_NULL_ERROR | Column '%s' cannot be null |
1062 | ER_DUP_ENTRY | Duplicate entry '%s' for key %d |
1242 | ER_SUBQUERY_NO_1_ROW | Subquery returns more than 1
row |
1264 | ER_WARN_DATA_OUT_OF_RANGE | Out of range value for
column '%s' at row %ld |
1265 | WARN_DATA_TRUNCATED | Data truncated for column
'%s' at row %ld |
1292 | ER_TRUNCATED_WRONG_VALUE | Truncated incorrect %s
value: '%s' |
1366 | ER_TRUNCATED_WRONG_VALUE_FOR_FIELD | Incorrect
integer value |
1369 | ER_VIEW_CHECK_FAILED | CHECK OPTION failed '%s.%s'
|
1451 | ER_ROW_IS_REFERENCED_2 | Cannot delete or update a
parent row |
1452 | ER_NO_REFERENCED_ROW_2 | Cannot add or update a child
row: a foreign key constraint fails (%s) |
1526 | ER_NO_PARTITION_FOR_GIVEN_VALUE | Table has no
partition for value %s |
1586 | ER_DUP_ENTRY_WITH_KEY_NAME | Duplicate entry '%s'
for key '%s' |
1591 | ER_NO_PARTITION_FOR_GIVEN_VALUE_SILENT | Table has no
partition for some existing values |
1748 | ER_ROW_DOES_NOT_MATCH_GIVEN_PARTITION_SET | Found a
row not matching the given partition set |
Ignored errors normally generate a warning.
A property of the IGNORE clause consists in causing
transactional engines and non-transactional engines (like
XtraDB and Aria) to behave the same way. For example,
normally a multi-row insert which tries to violate a UNIQUE
contraint is completely rolled back on XtraDB/InnoDB, but
might be partially executed on Aria. With the IGNORE clause,
the statement will be partially executed in both engines.
Starting from MariaDB 5.5.28 duplicate key errors also
generate warnings. The OLD_MODE server variable can be used
to prevent this.
URL: https://mariadb.com/kb/en/ignore/https://mariadb.com/kb/en/ignore/ �H
���` ��
� ! INSERTSyntax
------
INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
[INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
{VALUES | VALUE} ({expr | DEFAULT},...),(...),...
[ ON DUPLICATE KEY UPDATE
col=expr
[, col=expr] ... ]
Or:
INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
[INTO] tbl_name [PARTITION (partition_list)]
SET col={expr | DEFAULT}, ...
[ ON DUPLICATE KEY UPDATE
col=expr
[, col=expr] ... ]
Or:
INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
[INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
SELECT ...
[ ON DUPLICATE KEY UPDATE
col=expr
[, col=expr] ... ]
The INSERT statement is used to insert new rows into an
existing table. The INSERT ... VALUES
and INSERT ... SET forms of the statement insert rows based
on explicitly specified values. The INSERT ... SELECT form
inserts rows selected from another table or tables. INSERT
... SELECT is discussed further in the INSERT ... SELECT
article.
The table name can be specified in the form db_name.tbl_name
or, if a default database is selected, in the form tbl_name
(see Identifier Qualifiers). This allows to use INSERT ...
SELECT to copy rows between different databases.
The PARTITION clause was introduced in MariaDB 10.0. It can
be used in both the INSERT and the SELECT part. See
Partition Pruning and Selection for details.
The columns list is optional. It specifies which values are
explicitly inserted, and in which order. If this clause is
not specified, all values must be explicitly specified, in
the same order they are listed in the table definition.
The list of value follow the VALUES or VALUE keyword (which
are interchangeable, regardless how much values you want to
insert), and is wrapped by parenthesis. The values must be
listed in the same order as the columns list. It is possible
to specify more than one list to insert more than one rows
with a single statement. If many rows are inserted, this is
a speed optimization.
For one-row statements, the SET clause may be more simple,
because you don't need to remember the columns order. All
values are specified in the form col = expr.
Values can also be specified in the form of a SQL expression
or subquery. However, the subquery cannot access the same
table that is named in the INTO clause.
If you use the LOW_PRIORITY keyword, execution of the INSERT
is delayed until no other clients are reading from the
table. If you use the HIGH_PRIORITY keyword, the statement
has the same priority as SELECTs. This affects only storage
engines that use only table-level locking (MyISAM, MEMORY,
MERGE). However, if one of these keywords is specified,
concurrent inserts cannot be used. See HIGH_PRIORITY and
LOW_PRIORITY clauses for details.
INSERT DELAYED
For more details on the DELAYED option, see INSERT DELAYED.
HIGH PRIORITY and LOW PRIORITY
See HIGH_PRIORITY and LOW_PRIORITY.
Defaults and Duplicate Values
See INSERT - Default & Duplicate Values for details..
INSERT IGNORE
See INSERT IGNORE.
INSERT ON DUPLICATE KEY UPDATE
See INSERT ON DUPLICATE KEY UPDATE.
Examples
--------
Specifying the column names:
INSERT INTO person (first_name, last_name) VALUES ('John',
'Doe');
Inserting more than 1 row at a time:
INSERT INTO tbl_name VALUES (1, "row 1"), (2, "row 2");
Using the SET clause:
INSERT INTO person SET first_name = 'John', last_name =
'Doe';
SELECTing from another table:
INSERT INTO contractor SELECT * FROM person WHERE status =
'c';
See INSERT ON DUPLICATE KEY UPDATE and INSERT IGNORE for
further examples.
URL: https://mariadb.com/kb/en/insert/https://mariadb.com/kb/en/insert/ � '<: INSERT - Default & Duplicate ValuesDefault Values
If the SQL_MODE contains STRICT_TRANS_TABLES and you are
inserting into a transactional table (like InnoDB), or if
the SQL_MODE contains STRICT_ALL_TABLES, all NOT NULL
columns which does not have a DEFAULT value (and is not
AUTO_INCREMENT) must be explicitly referenced in INSERT
statements. If not, an error like this is produced:
ERROR 1364 (HY000): Field 'col' doesn't have a default
value
In all other cases, if a NOT NULL column without a DEFAULT
value is not referenced, an empty value will be inserted
(for example, 0 for INTEGER columns and '' for CHAR
columns). See NULL Values in MariaDB:Inserting for examples.
If a NOT NULL column having a DEFAULT value is not
referenced, NULL will be inserted.
If a NULL column having a DEFAULT value is not referenced,
its default value will be inserted. It is also possible to
explicitly assign the default value using the DEFAULT
keyword or the DEFAULT() function.
If the DEFAULT keyword is used but the column does not have
a DEFAULT value, an error like this is produced:
ERROR 1364 (HY000): Field 'col' doesn't have a default
value
Duplicate Values
By default, if you try to insert a duplicate row and there
is a UNIQUE index, INSERT stops and an error like this is
produced:
ERROR 1062 (23000): Duplicate entry 'dup_value' for key
'col'
To handle duplicates you can use the IGNORE clause, INSERT
ON DUPLICATE KEY UPDATE or the REPLACE statement. Note that
the IGNORE and DELAYED options are ignored when you use ON
DUPLICATE KEY UPDATE.
URL:
https://mariadb.com/kb/en/insert-default-duplicate-values/https://mariadb.com/kb/en/insert-default-duplicate-values/ U� I �r �� � �
) INSERT DELAYEDSyntax
------
INSERT DELAYED ...
Description
-----------
The DELAYED option for the INSERT
statement is a MariaDB/MySQL extension to standard SQL that
is very useful if you have
clients that cannot or need not wait for the INSERT to
complete. This is a common situation when you use MariaDB
for logging and you
also periodically run SELECT and UPDATE
statements that take a long time to complete.
When a client uses INSERT DELAYED, it gets an okay from the
server at once, and the row is queued to be inserted when
the table is not in
use by any other thread.
Another major benefit of using INSERT DELAYED is that
inserts from many clients are bundled together and written
in one block. This
is much faster than performing many separate inserts.
Note that INSERT DELAYED is slower than a normal
INSERT if the table is not otherwise in use. There is also
the additional overhead for the server to handle a separate
thread for each
table for which there are delayed rows. This means that you
should use
INSERT DELAYED only when you are really sure that you need
it.
The queued rows are held only in memory until they are
inserted into the table.
This means that if you terminate mysqld forcibly (for
example, with kill -9) or
if mysqld dies unexpectedly, any queued rows that have not
been written to disk
are lost.
The number of concurrent INSERT DELAYED threads is limited
by the max_delayed_threads server system variables. If it is
set to 0, INSERT DELAYED is disabled. The session value can
be equal to the global value, or 0 to disable this statement
for the current session. If this limit has been reached, the
DELAYED clause will be silently ignore for subsequent
statements (no error will be produced).
There are some constraints on the use of DELAYED:
INSERT DELAYED works only with MyISAM, MEMORY, ARCHIVE,
and BLACKHOLE tables. If you execute INSERT DELAYED with
another storage engine, you will get an error like this:
ERROR 1616 (HY000): DELAYED option not supported for table
'tab_name'
For MyISAM tables, if there are no free blocks in the middle
of the data
file, concurrent SELECT and INSERT statements are
supported. Under these
circumstances, you very seldom need to use INSERT DELAYED
with MyISAM.
INSERT DELAYED should be used only for
INSERT statements that specify value lists. The server
ignores DELAYED for INSERT ... SELECT
or INSERT ... ON DUPLICATE KEY UPDATE statements.
Because the INSERT DELAYED statement returns immediately,
before the rows are inserted, you cannot use
LAST_INSERT_ID() to get the
AUTO_INCREMENT value that the statement might generate.
DELAYED rows are not visible to SELECT
statements until they actually have been inserted.
After INSERT DELAYED, ROW_COUNT() returns the number of the
rows you tried to insert, not the number of the successful
writes.
DELAYED is ignored on slave replication servers, so that
INSERT DELAYED is treated as a normal
INSERT on slaves. This is because
DELAYED could cause the slave to have different data than
the master. INSERT DELAYED statements are not safe for
replication.
Pending INSERT DELAYED statements are lost if a table is
write locked and ALTER TABLE is used to modify the table
structure.
INSERT DELAYED is not supported for views. If you try, you
will get an error like this: ERROR 1347 (HY000):
'view_name' is not BASE TABLE
INSERT DELAYED is not supported for partitioned tables.
INSERT DELAYED is not supported within stored programs.
URL: https://mariadb.com/kb/en/insert-delayed/https://mariadb.com/kb/en/insert-delayed/ �
( INSERT IGNOREIgnoring Errors
Normally INSERT stops and rolls back when it encounters an
error.
By using the IGNORE keyword all errors are converted to
warnings, which will not stop inserts of additional rows.
The IGNORE and DELAYED options are ignored when you use ON
DUPLICATE KEY UPDATE.
Incompatibilities
MariaDB until 5.5.28
MySQL and MariaDB before 5.5.28 didn't give warnings for
duplicate key errors when using IGNORE.
You can get the old behaviour if you set OLD_MODE to
NO_DUP_KEY_WARNINGS_WITH_IGNORE
Examples
--------
CREATE TABLE t1 (x INT UNIQUE);
INSERT INTO t1 VALUES(1),(2);
INSERT INTO t1 VALUES(2),(3);
ERROR 1062 (23000): Duplicate entry '2' for key 'x'
SELECT * FROM t1;
+------+
| x |
+------+
| 1 |
| 2 |
+------+
2 rows in set (0.00 sec)
INSERT IGNORE INTO t1 VALUES(2),(3);
Query OK, 1 row affected, 1 warning (0.04 sec)
SHOW WARNINGS;
+---------+------+---------------------------------+
| Level | Code | Message |
+---------+------+---------------------------------+
| Warning | 1062 | Duplicate entry '2' for key 'x' |
+---------+------+---------------------------------+
SELECT * FROM t1;
+------+
| x |
+------+
| 1 |
| 2 |
| 3 |
+------+
See INSERT ON DUPLICATE KEY UPDATE for further examples
using that syntax.
URL: https://mariadb.com/kb/en/insert-ignore/https://mariadb.com/kb/en/insert-ignore/ a N�օ �� � �9 INSERT ON DUPLICATE KEY UPDATESyntax
------
INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
[INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
{VALUES | VALUE} ({expr | DEFAULT},...),(...),...
[ ON DUPLICATE KEY UPDATE
col=expr
[, col=expr] ... ]
Or:
INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
[INTO] tbl_name [PARTITION (partition_list)]
SET col={expr | DEFAULT}, ...
[ ON DUPLICATE KEY UPDATE
col=expr
[, col=expr] ... ]
Or:
INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
[INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
SELECT ...
[ ON DUPLICATE KEY UPDATE
col=expr
[, col=expr] ... ]
Description
-----------
INSERT ... ON DUPLICATE KEY UPDATE is a MariaDB/MySQL
extension to the INSERT statement that, if it finds a
duplicate unique or primary key, will instead perform an
UPDATE.
The row/s affected value is reported as 1 if a row is
inserted, and 2 if a row is updated, unless the API's
CLIENT_FOUND_ROWS flag is set.
If more than one unique index is matched, only the first is
updated. It is not recommended to use this statement on
tables with more than one unique index.
If the table has an AUTO_INCREMENT primary key and the
statement inserts or updates a row, the LAST_INSERT_ID()
function returns its AUTO_INCREMENT value.
The VALUES() function can only be used in a ON DUPLICATE KEY
UPDATE clause and has no meaning in any other context. It
returns the column values from the INSERT portion of the
statement. This function is particularly useful for
multi-rows inserts.
The IGNORE and DELAYED options are ignored when you use ON
DUPLICATE KEY UPDATE.
The PARTITION clause was introduced in MariaDB 10.0. See
Partition Pruning and Selection for details.
This statement activates INSERT and UPDATE triggers. See
Trigger Overview for details.
See also a similar statement, REPLACE.
Examples
--------
CREATE TABLE ins_duplicate (id INT PRIMARY KEY, animal
VARCHAR(30));
INSERT INTO ins_duplicate VALUES (1,'Aardvark'),
(2,'Cheetah'), (3,'Zebra');
If there is no existing key, the statement runs as a regular
INSERT:
INSERT INTO ins_duplicate VALUES (4,'Gorilla') ON
DUPLICATE KEY UPDATE animal='Gorilla';
Query OK, 1 row affected (0.07 sec)
SELECT * FROM ins_duplicate;
+----+----------+
| id | animal |
+----+----------+
| 1 | Aardvark |
| 2 | Cheetah |
| 3 | Zebra |
| 4 | Gorilla |
+----+----------+
A regular INSERT with a primary key value of 1 will fail,
due to the existing key:
INSERT INTO ins_duplicate VALUES (1,'Antelope');
ERROR 1062 (23000): Duplicate entry '1' for key
'PRIMARY'
However, we can use an INSERT ON DUPLICATE KEY UPDATE
instead:
INSERT INTO ins_duplicate VALUES (1,'Antelope') ON
DUPLICATE KEY UPDATE animal='Antelope';
Query OK, 2 rows affected (0.09 sec)
Note that there are two rows reported as affected, but this
refers only to the UPDATE.
SELECT * FROM ins_duplicate;
+----+----------+
| id | animal |
+----+----------+
| 1 | Antelope |
| 2 | Cheetah |
| 3 | Zebra |
| 4 | Gorilla |
+----+----------+
Adding a second unique column:
ALTER TABLE ins_duplicate ADD id2 INT;
UPDATE ins_duplicate SET id2=id+10;
ALTER TABLE ins_duplicate ADD UNIQUE KEY(id2);
Where two rows match the unique keys match, only the first
is updated. This can be unsafe and is not recommended unless
you are certain what you are doing. Note that the warning
shown below appears in MariaDB 5.5 and before, but has been
removed in MariaDB 10.0, as MariaDB now assumes that the
keys are checked in order, as shown in SHOW CREATE TABLE.
INSERT INTO ins_duplicate VALUES (2,'Lion',13) ON
DUPLICATE KEY UPDATE animal='Lion';
Query OK, 2 rows affected, 1 warning (0.06 sec)
SHOW WARNINGS;
+-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level | Code | Message |
+-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Note | 1592 | Unsafe statement written to the binary log
using statement format since BINLOG_FORMAT = STATEMENT.
INSERT... ON DUPLICATE KEY UPDATE on a table with more than
one UNIQUE KEY is unsafe |
+-------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
SELECT * FROM ins_duplicate;
+----+----------+------+
| id | animal | id2 |
+----+----------+------+
| 1 | Antelope | 11 |
| 2 | Lion | 12 |
| 3 | Zebra | 13 |
| 4 | Gorilla | 14 |
+----+----------+------+
Although the third row with an id of 3 has an id2 of 13,
which also matched, it was not updated.
Changing id to an auto_increment field. If a new row is
added, the auto_increment is moved forward. If the row is
updated, it remains the same.
ALTER TABLE `ins_duplicate` CHANGE `id` `id` INT( 11 ) NOT
NULL AUTO_INCREMENT;
ALTER TABLE ins_duplicate DROP id2;
SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES WHERE
TABLE_NAME='ins_duplicate';
+----------------+
| Auto_increment |
+----------------+
| 5 |
+----------------+
INSERT INTO ins_duplicate VALUES (2,'Leopard') ON
DUPLICATE KEY UPDATE animal='Leopard';
Query OK, 2 rows affected (0.00 sec)
SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES WHERE
TABLE_NAME='ins_duplicate';
+----------------+
| Auto_increment |
+----------------+
| 5 |
+----------------+
INSERT INTO ins_duplicate VALUES (5,'Wild Dog') ON
DUPLICATE KEY UPDATE animal='Wild Dog';
Query OK, 1 row affected (0.09 sec)
SELECT * FROM ins_duplicate;
+----+----------+
| id | animal |
+----+----------+
| 1 | Antelope |
| 2 | Leopard |
| 3 | Zebra |
| 4 | Gorilla |
| 5 | Wild Dog |
+----+----------+
SELECT Auto_increment FROM INFORMATION_SCHEMA.TABLES WHERE
TABLE_NAME='ins_duplicate';
+----------------+
| Auto_increment |
+----------------+
| 6 |
+----------------+
Refering to column values from the INSERT portion of the
statement:
INSERT INTO table (a,b,c) VALUES (1,2,3),(4,5,6)
ON DUPLICATE KEY UPDATE c=VALUES(a)+VALUES(b);
See the VALUES() function for more.
URL:
https://mariadb.com/kb/en/insert-on-duplicate-key-update/https://mariadb.com/kb/en/insert-on-duplicate-key-update/ �
B �� �
M( INSERT SELECTSyntax
------
INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
[INTO] tbl_name [(col_name,...)]
SELECT ...
[ ON DUPLICATE KEY UPDATE col_name=expr, ... ]
Description
-----------
With INSERT ... SELECT, you can quickly insert many rows
into a table from one or more other tables. For example:
INSERT INTO tbl_temp2 (fld_id)
SELECT tbl_temp1.fld_order_id
FROM tbl_temp1 WHERE tbl_temp1.fld_order_id > 100;
tbl_name can also be specified in the form db_name.tbl_name
(see Identifier Qualifiers). This allows to copy rows
between different databases.
If the new table has a primary key or UNIQUE indexes, you
can use IGNORE to handle duplicate key errors during the
query. The newer values will not be inserted if an identical
value already exists.
REPLACE can be used instead of INSERT to prevent duplicates
on UNIQUE indexes by deleting old values. In that case, ON
DUPLICATE KEY UPDATE cannot be used.
INSERT ... SELECT works for tables which already exist. To
create a table for a given resultset, you can use CREATE
TABLE ... SELECT.
URL: https://mariadb.com/kb/en/insert-select/https://mariadb.com/kb/en/insert-select/ � $ INTERSECTINTERSECT was introduced in MariaDB 10.3.0.
The result of an intersect is the intersection of right and
left SELECT results, i.e. only records that are present in
both result sets will be included in the result of the
operation.
Syntax
------
SELECT ...
(INTERSECT | EXCEPT | UNION [ALL | DISTINCT]) SELECT ...
[(INTERSECT | EXCEPT | UNION [ALL | DISTINCT]) SELECT ...]
[ORDER BY [column [, column ...]]]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]
Please note:
ALL is not supported by INTERSECT (and it is difficult to
make sense of ALL with INTERSECT).
Brackets for explicit operation precedence are not
supported; use a subquery in the FROM clause as a
workaround).
Description
-----------
MariaDB has supported INTERSECT (as well as EXCEPT) in
addition to UNION since MariaDB 10.3.
All behavior for naming columns, ORDER BY and LIMIT is the
same as for UNION.
INTERSECT implicitly supposes a DISTINCT operation.
The result of an intersect is the intersection of right and
left SELECT results, i.e. only records that are present in
both result sets will be included in the result of the
operation.
INTERSECT has higher precedence than UNION and EXCEPT. If
possible it will be executed linearly but if not it will be
translated to a subquery in the FROM clause:
(select a,b from t1)
union
(select c,d from t2)
intersect
(select e,f from t3)
union
(select 4,4);
will be translated to:
(select a,b from t1)
union
select c,d from
((select c,d from t2)
intersect
(select e,f from t3)) dummy_subselect
union
(select 4,4)
Parentheses
From MariaDB 10.4.0, parentheses can be used to specify
precedence. Before this, a syntax error would be returned.
Examples
--------
Show customers which are employees:
(SELECT e_name AS name, email FROM employees)
INTERSECT
(SELECT c_name AS name, email FROM customers);
Difference between UNION, EXCEPT and INTERSECT:
CREATE TABLE seqs (i INT);
INSERT INTO seqs VALUES (1),(2),(3),(4),(5),(6);
SELECT i FROM seqs WHERE i =3;
+------+
| i |
+------+
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
| 6 |
+------+
SELECT i FROM seqs WHERE i =3;
+------+
| i |
+------+
| 1 |
| 2 |
+------+
SELECT i FROM seqs WHERE i =3;
+------+
| i |
+------+
| 3 |
+------+
Parentheses for specifying precedence, from MariaDB 10.4.0
CREATE OR REPLACE TABLE t1 (a INT);
CREATE OR REPLACE TABLE t2 (b INT);
CREATE OR REPLACE TABLE t3 (c INT);
INSERT INTO t1 VALUES (1),(2),(3),(4);
INSERT INTO t2 VALUES (5),(6);
INSERT INTO t3 VALUES (1),(6);
((SELECT a FROM t1) UNION (SELECT b FROM t2)) INTERSECT
(SELECT c FROM t3);
+------+
| a |
+------+
| 1 |
| 6 |
+------+
(SELECT a FROM t1) UNION ((SELECT b FROM t2) INTERSECT
(SELECT c FROM t3));
+------+
| a |
+------+
| 1 |
| 2 |
| 3 |
| 4 |
| 6 |
+------+
URL: https://mariadb.com/kb/en/intersect/https://mariadb.com/kb/en/intersect/ � M & JOIN SyntaxDescription
-----------
MariaDB supports the following JOIN syntaxes for
the table_references part of SELECT statements and
multiple-table DELETE and UPDATE statements:
table_references:
table_reference [, table_reference] ...
table_reference:
table_factor
| join_table
table_factor:
tbl_name [PARTITION (partition_list)]
[query_system_time_period_specification] [[AS] alias]
[index_hint_list]
| table_subquery [query_system_time_period_specification]
[AS] alias
| ( table_references )
| { ON table_reference LEFT OUTER JOIN table_reference
ON conditional_expr }
join_table:
table_reference [INNER | CROSS] JOIN table_factor
[join_condition]
| table_reference STRAIGHT_JOIN table_factor
| table_reference STRAIGHT_JOIN table_factor ON
conditional_expr
| table_reference {LEFT|RIGHT} [OUTER] JOIN table_reference
join_condition
| table_reference NATURAL [{LEFT|RIGHT} [OUTER]] JOIN
table_factor
join_condition:
ON conditional_expr
| USING (column_list)
query_system_time_period_specification:
FOR SYSTEM_TIME AS OF point_in_time
| FOR SYSTEM_TIME BETWEEN point_in_time AND point_in_time
| FOR SYSTEM_TIME FROM point_in_time TO point_in_time
| FOR SYSTEM_TIME ALL
point_in_time:
[TIMESTAMP] expression
| TRANSACTION expression
index_hint_list:
index_hint [, index_hint] ...
index_hint:
USE {INDEX|KEY}
[{FOR {JOIN|ORDER BY|GROUP BY}] ([index_list])
| IGNORE {INDEX|KEY}
[{FOR {JOIN|ORDER BY|GROUP BY}] (index_list)
| FORCE {INDEX|KEY}
[{FOR {JOIN|ORDER BY|GROUP BY}] (index_list)
index_list:
index_name [, index_name] ...
A table reference is also known as a join expression.
Each table can also be specified as db_name.tabl_name. This
allows to write queries which involve multiple databases.
See Identifier Qualifiers for syntax details.
The syntax of table_factor is extended in comparison with
the
SQL Standard. The latter accepts only table_reference, not a
list of them inside a pair of parentheses.
This is a conservative extension if we consider each comma
in a list of
table_reference items as equivalent to an inner join. For
example:
SELECT * FROM t1 LEFT JOIN (t2, t3, t4)
ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c)
is equivalent to:
SELECT * FROM t1 LEFT JOIN (t2 CROSS JOIN t3 CROSS JOIN t4)
ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c)
In MariaDB, CROSS JOIN is a syntactic equivalent to
INNER JOIN (they can replace each other). In standard SQL,
they are not equivalent. INNER JOIN is used with an
ON clause, CROSS JOIN is used otherwise.
In general, parentheses can be ignored in join expressions
containing only
inner join operations. MariaDB also supports nested joins
(see
http://dev.mysql.com/doc/refman/5.1/en/nested-join-optimization.html).
See System-versioned tables for more information
about FOR SYSTEM_TIME syntax.
Index hints can be specified to affect how the MariaDB
optimizer makes
use of indexes. For more information, see How to force query
plans.
Examples
--------
SELECT left_tbl.*
FROM left_tbl LEFT JOIN right_tbl ON left_tbl.id =
right_tbl.id
WHERE right_tbl.id IS NULL;
URL: https://mariadb.com/kb/en/join-syntax/https://mariadb.com/kb/en/join-syntax/ �� �A �� �� �2 � � LIMITDescription
-----------
Use the LIMIT clause to restrict the number of returned
rows. When you use a single
integer n with LIMIT, the first n rows will be returned. Use
the ORDER BY
clause to control which rows come first. You can also select
a number of rows after an offset
using either of the following:
LIMIT offset, row_count
LIMIT row_count OFFSET offset
When you provide an offset m with a limit n, the first m
rows will be ignored, and the
following n rows will be returned.
Executing an UPDATE with the LIMIT clause is not safe for
replication.
Since MariaDB 10.0.11, LIMIT 0 has been an exception to this
rule (see MDEV-6170).
Beginning in MariaDB 5.5.21, there is a LIMIT ROWS EXAMINED
optimization which provides the
means to terminate the execution of SELECT statements which
examine too
many rows, and thus use too many resources. See LIMIT ROWS
EXAMINED.
Multi-Table Updates
Until MariaDB 10.3.1, it was not possible to use LIMIT (or
ORDER BY) in a multi-table UPDATE statement. This
restriction was lifted in MariaDB 10.3.2.
GROUP_CONCAT
Starting from MariaDB 10.3.3, it is possible to use LIMIT
with GROUP_CONCAT().
Examples
--------
CREATE TABLE members (name VARCHAR(20));
INSERT INTO members
VALUES('Jagdish'),('Kenny'),('Rokurou'),('Immaculada');
SELECT * FROM members;
+------------+
| name |
+------------+
| Jagdish |
| Kenny |
| Rokurou |
| Immaculada |
+------------+
Select the first two names (no ordering specified):
SELECT * FROM members LIMIT 2;
+---------+
| name |
+---------+
| Jagdish |
| Kenny |
+---------+
All the names in alphabetical order:
SELECT * FROM members ORDER BY name;
+------------+
| name |
+------------+
| Immaculada |
| Jagdish |
| Kenny |
| Rokurou |
+------------+
The first two names, ordered alphabetically:
SELECT * FROM members ORDER BY name LIMIT 2;
+------------+
| name |
+------------+
| Immaculada |
| Jagdish |
+------------+
The third name, ordered alphabetically (the first name would
be offset zero, so the third is offset two):
SELECT * FROM members ORDER BY name LIMIT 2,1;
+-------+
| name |
+-------+
| Kenny |
+-------+
From MariaDB 10.3.2, LIMIT can be used in a multi-table
update:
CREATE TABLE warehouse (product_id INT, qty INT);
INSERT INTO warehouse VALUES
(1,100),(2,100),(3,100),(4,100);
CREATE TABLE store (product_id INT, qty INT);
INSERT INTO store VALUES (1,5),(2,5),(3,5),(4,5);
UPDATE warehouse,store SET warehouse.qty = warehouse.qty-2,
store.qty = store.qty+2
WHERE (warehouse.product_id = store.product_id AND
store.product_id >= 1)
ORDER BY store.product_id DESC LIMIT 2;
SELECT * FROM warehouse;
+------------+------+
| product_id | qty |
+------------+------+
| 1 | 100 |
| 2 | 100 |
| 3 | 98 |
| 4 | 98 |
+------------+------+
SELECT * FROM store;
+------------+------+
| product_id | qty |
+------------+------+
| 1 | 5 |
| 2 | 5 |
| 3 | 7 |
| 4 | 7 |
+------------+------+
From MariaDB 10.3.3, LIMIT can be used with GROUP_CONCAT,
so, for example, given the following table:
CREATE TABLE d (dd DATE, cc INT);
INSERT INTO d VALUES ('2017-01-01',1);
INSERT INTO d VALUES ('2017-01-02',2);
INSERT INTO d VALUES ('2017-01-04',3);
the following query:
SELECT SUBSTRING_INDEX(GROUP_CONCAT(CONCAT_WS(":",dd,cc)
ORDER BY cc DESC),",",1) FROM d;
+----------------------------------------------------------------------------+
| SUBSTRING_INDEX(GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER
BY cc DESC),",",1) |
+----------------------------------------------------------------------------+
| 2017-01-04:3 |
+----------------------------------------------------------------------------+
can be more simply rewritten as:
SELECT GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC
LIMIT 1) FROM d;
+-------------------------------------------------------------+
| GROUP_CONCAT(CONCAT_WS(":",dd,cc) ORDER BY cc DESC LIMIT
1) |
+-------------------------------------------------------------+
| 2017-01-04:3 |
+-------------------------------------------------------------+
URL: https://mariadb.com/kb/en/limit/https://mariadb.com/kb/en/limit/ � ] # LOAD XMLSyntax
------
LOAD XML [LOW_PRIORITY | CONCURRENT] [LOCAL] INFILE
'file_name'
[REPLACE | IGNORE]
INTO TABLE [db_name.]tbl_name
[CHARACTER SET charset_name]
[ROWS IDENTIFIED BY '']
[IGNORE number {LINES | ROWS}]
[(column_or_user_var,...)]
[SET col_name = expr,...]
Description
-----------
The LOAD XML statement reads data from an XML file into a
table. The
file_name must be given as a literal string. The tagname in
the
optional ROWS IDENTIFIED BY clause must also be given as a
literal
string, and must be surrounded by angle brackets (< and >).
LOAD XML acts as the complement of running the mysql client
in XML
output mode (that is, starting the client with the --xml
option). To
write data from a table to an XML file, use a command such
as the
following one from the system shell:
shell> mysql --xml -e 'SELECT * FROM mytable' > file.xml
To read the file back into a table, use LOAD XML INFILE. By
default,
the element is considered to be the equivalent of a
database
table row; this can be changed using the ROWS IDENTIFIED BY
clause.
This statement supports three different XML formats:
Column names as attributes and column values as attribute
values:
Column names as tags and column values as the content of
these tags:
value1
value2
Column names are the name attributes of tags, and values
are
the contents of these tags:
value1
value2
This is the format used by other tools, such as mysqldump.
All 3 formats can be used in the same XML file; the import
routine
automatically detects the format for each row and interprets
it
correctly. Tags are matched based on the tag or attribute
name and the
column name.
The following clauses work essentially the same way for LOAD
XML as
they do for LOAD DATA:
LOW_PRIORITY or CONCURRENT
LOCAL
REPLACE or IGNORE
CHARACTER SET
(column_or_user_var,...)
SET
See LOAD DATA for more information about these clauses.
The IGNORE number LINES or IGNORE number ROWS clause causes
the first
number rows in the XML file to be skipped. It is analogous
to the LOAD
DATA statement's IGNORE ... LINES clause.
If the LOW_PRIORITY keyword is used, insertions are delayed
until no other clients are reading from the table. The
CONCURRENT keyword allowes the use of concurrent inserts.
These clauses cannot be specified together.
This statement activates INSERT triggers.
URL: https://mariadb.com/kb/en/load-xml/https://mariadb.com/kb/en/load-xml/ ,� �R� �� � �+ LOAD DATA INFILESyntax
------
LOAD DATA [LOW_PRIORITY | CONCURRENT] [LOCAL] INFILE
'file_name'
[REPLACE | IGNORE]
INTO TABLE tbl_name
[CHARACTER SET charset_name]
[{FIELDS | COLUMNS}
[TERMINATED BY 'string']
[[OPTIONALLY] ENCLOSED BY 'char']
[ESCAPED BY 'char']
]
[LINES
[STARTING BY 'string']
[TERMINATED BY 'string']
]
[IGNORE number LINES]
[(col_name_or_user_var,...)]
[SET col_name = expr,...]
Description
-----------
Reads rows from a text file into the designated table on the
database at a very high speed. The file name must be given
as a literal string.
Files are written to disk using the SELECT INTO OUTFILE
statement. You can then read the files back into a table
using the LOAD DATA INFILE statement. The FIELDS and LINES
clauses are the same in both statements. These clauses are
optional, but if both are specified then the FIELDS clause
must precede LINES.
In releases after MariaDB 5.5, LOAD DATA INFILE is unsafe
for statement-based replication.
Executing this statement activates INSERT triggers.
REPLACE and IGNORE
In cases where you load data from a file into a table that
already contains data and has a Primary Key, you may
encounter issues where the statement attempts to insert a
row with a Primary Key that already exists. When this
happens, the statement fails with Error 1064, protecting the
data already on the table. In cases where you want MariaDB
to overwrite duplicates, use the REPLACE keyword.
The REPLACE keyword works like the REPLACE statement. Here,
the statement attempts to load the data from the file. If
the row does not exist, it adds it to the table. If the row
contains an existing Primary Key, it replaces the table
data. That is, in the event of a conflict, it assumes the
file contains the desired row.
This operation can cause a degradation in load speed by a
factor of 20 or more if the part that has already been
loaded is larger than the capacity of the InnoDB Buffer
Pool. This happens because it causes a lot of turnaround in
the Buffer Pool.
Use the IGNORE keyword when you want to skip any rows that
contain a conflicting Primary Key. Here, the statement
attempts to load the data from the file. If the row does not
exist, it adds it to the table. If the row contains an
existing Primary Key, it ignores the addition request and
moves on to the next. That is, in the event of a conflict,
it assumes the table contains the desired row.
LOCAL
When you issue this statement, the Server attempts to read
files from the host file system. Using the LOCAL keyword,
the statement instead attempts to read files from the
client. This allows you to insert files from the client's
local file system into the database.
In the event that you don't want the server to permit this
operation, (such as for security reasons), you can disable
support using local_infile. When this system variable is set
to 0, MariaDB rejects LOAD DATA LOCAL INFILE statements,
failing with an error message.
Character-sets
When the statement opens the file, it attempts to read the
contents using the default character-set, as defined by the
character_set_database system variable.
In the cases where the file was written using a
character-set other than the default, you can specify the
character-set to use with the CHARACTER SET clause in the
statement. It ignores character-sets specified by the SET
NAMES statement and by the character_set_client system
variable. Setting the CHARACTER SET clause to a value of
binary indicates "no conversion."
The statement interprets all fields in the file as having
the same character-set, regardless of the column data type.
To properly interpret file contents, you must ensure that it
was written with the correct character-set. If you write a
data file with mysqldump -T or with the SELECT INTO OUTFILE
statement with the mysql client, be sure to use the
--default-character-set option, so that the output is
written with the desired character-set.
When using mixed character sets, use the CHARACTER SET
clause in both SELECT INTO OUTFILE and LOAD DATA INFILE to
ensure that MariaDB correctly interprets the escape
sequences.
The character_set_filesystem system variable controls the
interpretation of the filename.
It is currently not possible to load data files that use the
ucs2 character set.
Priority and Concurrency
In loading data from a file, there's a risk that the
statement will attempt insertions concurrent with reads from
another client, which can result in the read serving a
result-set that contains only part of the update from the
LOAD DATA INFILE statement.
Using the LOW_PRIORITY keyword, MariaDB delays insertions
until no other clients are reading from the table.
Alternatively, you can use the CONCURRENT keyword to perform
concurrent insertion.
The LOW_PRIORITY and CONCURRENT keywords are mutually
exclusive. They cannot be used in the same statement.
Progress Reporting
Since MariaDB 5.3, the LOAD DATA INFILE statement supports
progress reporting. You may find this useful when dealing
with long-running operations. Using another client you can
issue a SHOW PROCESSLIST query to check the progress of the
data load.
Using mysqlimport
MariaDB ships with a separate utility for loading data from
files: mysqlimport. It operates by sending LOAD DATA INFILE
statements to the server.
Using mysqlimport you can compress the file using the
--compress option, to get better performance over slow
networks, providing both the client and server support the
compressed protocol. Use the --local option to load from the
local file system.
Indexing
In cases where the storage engine supports ALTER TABLE...
DISABLE KEYS statements, the LOAD DATA INFILE statement
automatically disables indexes during the execution.
URL: https://mariadb.com/kb/en/load-data-infile/https://mariadb.com/kb/en/load-data-infile/ �)�� �� � /( J Non-Recursive Common Table Expressions OverviewCommon Table Expressions (CTEs) are a standard SQL feature,
and are essentially temporary named result sets. There are
two kinds of CTEs: Non-Recursive, which this article covers;
and Recursive.
Common table expressions were introduced in MariaDB 10.2.1.
Non-Recursive CTEs
The WITH keyword signifies a CTE. It is given a name,
followed by a body (the main query) as follows:
CTEs are similar to derived tables. For example
WITH engineers AS
( SELECT * FROM employees
WHERE dept = 'Engineering' )
SELECT * FROM engineers
WHERE ...
SELECT * FROM
( SELECT * FROM employees
WHERE dept = 'Engineering' ) AS engineers
WHERE
...
A non-recursive CTE is basically a query-local VIEW. There
are several advantages and caveats to them. The syntax is
more readable than nested FROM (SELECT ...).
A CTE can refer to another and it can be referenced from
multiple places.
A CTE referencing Another CTE
Using this format makes for a more readable SQL than a
nested FROM(SELECT ...) clause. Below is an example of this:
WITH engineers AS (
SELECT * FROM employees
WHERE dept IN('Development','Support') ),
eu_engineers AS ( SELECT * FROM engineers WHERE country
IN('NL',...) )
SELECT
...
FROM eu_engineers;
Multiple Uses of a CTE
This can be an 'anti-self join', for example:
WITH engineers AS (
SELECT * FROM employees
WHERE dept IN('Development','Support') )
SELECT * FROM engineers E1
WHERE NOT EXISTS
(SELECT 1 FROM engineers E2
WHERE E2.country=E1.country
AND E2.name E1.name );
Or, for year-over-year comparisons, for example:
WITH sales_product_year AS (
SELECT product, YEAR(ship_date) AS year,
SUM(price) AS total_amt
FROM item_sales
GROUP BY product, year )
SELECT *
FROM sales_product_year CUR,
sales_product_year PREV,
WHERE CUR.product=PREV.product
AND CUR.year=PREV.year + 1
AND CUR.total_amt > PREV.total_amt
Another use is to compare individuals against their group.
Below is an example of how this might be executed:
WITH sales_product_year AS (
SELECT product,
YEAR(ship_date) AS year,
SUM(price) AS total_amt
FROM item_sales
GROUP BY product, year
)
SELECT *
FROM sales_product_year S1
WHERE
total_amt >
(SELECT 0.1 * SUM(total_amt)
FROM sales_product_year S2
WHERE S2.year = S1.year)
URL:
https://mariadb.com/kb/en/non-recursive-common-table-expressions-overview/https://mariadb.com/kb/en/non-recursive-common-table-expressions-overview/ � # ORDER BYDescription
-----------
Use the ORDER BY clause to order a resultset, such as that
are returned from a SELECT
statement. You can specify just a column or use any
expression with functions. If you are
using the GROUP BY clause, you can use grouping functions in
ORDER BY.
Ordering is done after grouping.
You can use multiple ordering expressions, separated by
commas. Rows will be sorted by
the first expression, then by the second expression if they
have the same value for the
first, and so on.
You can use the keywords ASC and DESC after each ordering
expression to
force that ordering to be ascending or descending,
respectively. Ordering is ascending
by default.
You can also use a single integer as the ordering
expression. If you use an integer n,
the results will be ordered by the nth column in the select
expression.
When string values are compared, they are compared as if by
the STRCMP
function. STRCMP ignores trailing whitespace and may
normalize
characters and ignore case, depending on the collation in
use.
Starting from MariaDB 5.5.35 duplicated entries in the ORDER
BY clause are removed. MySQL 5.6 also removes duplicated
fields.
ORDER BY can also be used to order the activities of a
DELETE or UPDATE statement (usually with the LIMIT clause).
Until MariaDB 10.3.1, it was not possible to use ORDER BY
(or LIMIT) in a multi-table UPDATE statement. This
restriction was lifted in MariaDB 10.3.2.
Examples
--------
CREATE TABLE seq (i INT, x VARCHAR(1));
INSERT INTO seq VALUES (1,'a'), (2,'b'), (3,'b'),
(4,'f'), (5,'e');
SELECT * FROM seq ORDER BY i;
+------+------+
| i | x |
+------+------+
| 1 | a |
| 2 | b |
| 3 | b |
| 4 | f |
| 5 | e |
+------+------+
SELECT * FROM seq ORDER BY i DESC;
+------+------+
| i | x |
+------+------+
| 5 | e |
| 4 | f |
| 3 | b |
| 2 | b |
| 1 | a |
+------+------+
SELECT * FROM seq ORDER BY x,i;
+------+------+
| i | x |
+------+------+
| 1 | a |
| 2 | b |
| 3 | b |
| 5 | e |
| 4 | f |
+------+------+
ORDER BY in an UPDATE statement, in conjunction with LIMIT:
UPDATE seq SET x='z' WHERE x='b' ORDER BY i DESC LIMIT
1;
SELECT * FROM seq;
+------+------+
| i | x |
+------+------+
| 1 | a |
| 2 | b |
| 3 | z |
| 4 | f |
| 5 | e |
+------+------+
From MariaDB 10.3.2, ORDER BY can be used in a multi-table
update:
CREATE TABLE warehouse (product_id INT, qty INT);
INSERT INTO warehouse VALUES
(1,100),(2,100),(3,100),(4,100);
CREATE TABLE store (product_id INT, qty INT);
INSERT INTO store VALUES (1,5),(2,5),(3,5),(4,5);
UPDATE warehouse,store SET warehouse.qty = warehouse.qty-2,
store.qty = store.qty+2
WHERE (warehouse.product_id = store.product_id AND
store.product_id >= 1)
ORDER BY store.product_id DESC LIMIT 2;
SELECT * FROM warehouse;
+------------+------+
| product_id | qty |
+------------+------+
| 1 | 100 |
| 2 | 100 |
| 3 | 98 |
| 4 | 98 |
+------------+------+
SELECT * FROM store;
+------------+------+
| product_id | qty |
+------------+------+
| 1 | 5 |
| 2 | 5 |
| 3 | 7 |
| 4 | 7 |
+------------+------+
URL: https://mariadb.com/kb/en/order-by/https://mariadb.com/kb/en/order-by/ � K � J�| � � +F Recursive Common Table Expressions OverviewRecursive Common Table Expressions have been supported since
MariaDB 10.2.2.
Common Table Expressions (CTEs) are a standard SQL feature,
and are essentially temporary named result sets. CTEs first
appeared in the SQL standard in 1999, and the first
implementations began appearing in 2007.
There are two kinds of CTEs:
Non-recursive
Recursive, which this article covers.
SQL is generally poor at recursive structures.
CTEs permit a query to reference itself. A recursive CTE
will repeatedly execute subsets of the data until it obtains
the complete result set. This makes it particularly useful
for handing hierarchical or tree-structured data.
Syntax example
WITH RECURSIVE signifies a recursive CTE. It is given a
name, followed by a body (the main query) as follows:
Computation
Given the following structure:
First execute the anchor part of the query:
Next, execute the recursive part of the query:
Summary so far
with recursive R as (
select anchor_data
union [all]
select recursive_part
from R, ...
)
select ...
Compute anchor_data
Compute recursive_part to get the new data
if (new data is non-empty) goto 2;
CAST to avoid truncating data
As currently implemented by MariaDB and by the SQL Standard,
data may be truncated if not correctly cast. It is necessary
to CAST the column to the correct width if the CTE's
recursive part produces wider values for a column than the
CTE's nonrecursive part. Some other DBMS give an error in
this situation, and MariaDB's behavior may change in future
- see MDEV-12325. See the examples below.
Examples
--------
Transitive closure - determining bus destinations
Sample data:
CREATE TABLE bus_routes (origin varchar(50), dst
varchar(50));
INSERT INTO bus_routes VALUES
('New York', 'Boston'),
('Boston', 'New York'),
('New York', 'Washington'),
('Washington', 'Boston'),
('Washington', 'Raleigh');
Now, we want to return the bus destinations with New York as
the origin:
WITH RECURSIVE bus_dst as (
SELECT origin as dst FROM bus_routes WHERE origin='New
York'
UNION
SELECT bus_routes.dst FROM bus_routes, bus_dst WHERE
bus_dst.dst= bus_routes.origin
)
SELECT * FROM bus_dst;
+------------+
| dst |
+------------+
| New York |
| Boston |
| Washington |
| Raleigh |
+------------+
The above example is computed as follows:
First, the anchor data is calculated:
Starting from New York
Boston and Washington are added
Next, the recursive part:
Starting from Boston and then Washington
Raleigh is added
UNION excludes nodes that are already present.
Computing paths - determining bus routes
This time, we are trying to get bus routes such as “New
York -> Washington -> Raleigh”.
Using the same sample data as the previous example:
WITH RECURSIVE paths (cur_path, cur_dest) AS (
SELECT origin, origin FROM bus_routes WHERE origin='New
York'
UNION
SELECT CONCAT(paths.cur_path, ',', bus_routes.dst),
bus_routes.dst
FROM paths, bus_routes
WHERE paths.cur_dest = bus_routes.origin AND
LOCATE(bus_routes.dst, paths.cur_path)=0
)
SELECT * FROM paths;
+-----------------------------+------------+
| cur_path | cur_dest |
+-----------------------------+------------+
| New York | New York |
| New York,Boston | Boston |
| New York,Washington | Washington |
| New York,Washington,Boston | Boston |
| New York,Washington,Raleigh | Raleigh |
+-----------------------------+------------+
CAST to avoid data truncation
In the following example, data is truncated because the
results are not specifically cast to a wide enough type:
WITH RECURSIVE tbl AS (
SELECT NULL AS col
UNION
SELECT "THIS NEVER SHOWS UP" AS col FROM tbl
)
+------+
| col |
+------+
| NULL |
| |
+------+
Explicitly use CAST to overcome this:
WITH RECURSIVE tbl AS (
SELECT CAST(NULL AS CHAR(50)) AS col
UNION SELECT "THIS NEVER SHOWS UP" AS col FROM tbl
)
SELECT * FROM tbl;
+---------------------+
| col |
+---------------------+
| NULL |
| THIS NEVER SHOWS UP |
+---------------------+
URL:
https://mariadb.com/kb/en/recursive-common-table-expressions-overview/https://mariadb.com/kb/en/recursive-common-table-expressions-overview/ � " REPLACESyntax
------
REPLACE [LOW_PRIORITY | DELAYED]
[INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
{VALUES | VALUE} ({expr | DEFAULT},...),(...),...
Or:
REPLACE [LOW_PRIORITY | DELAYED]
[INTO] tbl_name [PARTITION (partition_list)]
SET col={expr | DEFAULT}, ...
Or:
REPLACE [LOW_PRIORITY | DELAYED]
[INTO] tbl_name [PARTITION (partition_list)] [(col,...)]
SELECT ...
Description
-----------
REPLACE works exactly like
INSERT, except that if an old row in the table
has the same value as a new row for a PRIMARY KEY or a
UNIQUE index, the old row is deleted before the new row is
inserted. If the table has more than one UNIQUE keys, it is
possible that the new row conflicts with more than one row.
In this case, all conflicting rows will be deleted.
The table name can be specified in the form db_name.tbl_name
or, if a default database is selected, in the form tbl_name
(see Identifier Qualifiers). This allows to use REPLACE ...
SELECT to copy rows between different databases.
Basically it works like this:
BEGIN;
SELECT 1 FROM t1 WHERE key=# FOR UPDATE;
IF found-row
DELETE FROM t1 WHERE key=# ;
INSERT INTO t1 VALUES (...);
ENDIF
END;
The above can be replaced with:
REPLACE INTO t1 VALUES (...)
REPLACE is a MariaDB/MySQL extension to the SQL standard.
It
either inserts, or deletes and inserts. For other
MariaDB/MySQL extensions to
standard SQL --- that also handle duplicate values --- see
IGNORE and INSERT ON DUPLICATE KEY UPDATE.
Note that unless the table has a PRIMARY KEY or
UNIQUE index, using a REPLACE statement
makes no sense. It becomes equivalent to INSERT, because
there is no index to be used to determine whether a new row
duplicates another.
Values for all columns are taken from the values specified
in the
REPLACE statement. Any missing columns are set to their
default values, just as happens for INSERT. You cannot refer
to values from the current row and use them in the new row.
If you use an
assignment such as 'SET col = col + 1', the
reference to the column name on the right hand side is
treated as
DEFAULT(col), so the assignment is equivalent to
'SET col = DEFAULT(col) + 1'.
To use REPLACE, you must have both the
INSERT and DELETE privileges
for the table.
There are some gotchas you should be aware of, before using
REPLACE:
If there is an AUTO_INCREMENT field, a new value will be
generated.
If there are foreign keys, ON DELETE action will be
activated by REPLACE.
Triggers on DELETE and INSERT will be activated by REPLACE.
To avoid some of these behaviors, you can use INSERT ... ON
DUPLICATE KEY UPDATE.
The PARTITION clause was introduced in MariaDB 10.0. See
Partition Pruning and Selection for details.
This statement activates INSERT and DELETE triggers. See
Trigger Overview for details.
URL: https://mariadb.com/kb/en/replace/https://mariadb.com/kb/en/replace/ �T ���;z � � �! SELECTSyntax
------
SELECT
[ALL | DISTINCT | DISTINCTROW]
[HIGH_PRIORITY]
[STRAIGHT_JOIN]
[SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT]
[SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS]
select_expr [, select_expr ...]
[ FROM table_references
[WHERE where_condition]
[GROUP BY {col_name | expr | position} [ASC | DESC], ...
[WITH ROLLUP]]
[HAVING where_condition]
[ORDER BY {col_name | expr | position} [ASC | DESC], ...]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]
procedure|[PROCEDURE procedure_name(argument_list)]
[INTO OUTFILE 'file_name' [CHARACTER SET charset_name]
[export_options]
INTO DUMPFILE 'file_name' | INTO var_name [, var_name] ] |
[[FOR UPDATE | LOCK IN SHARE MODE] [WAIT n | NOWAIT] ] ]
export_options:
[{FIELDS | COLUMNS}
[TERMINATED BY 'string']
[[OPTIONALLY] ENCLOSED BY 'char']
[ESCAPED BY 'char']
]
[LINES
[STARTING BY 'string']
[TERMINATED BY 'string']
]
Description
-----------
SELECT is used to retrieve rows selected from one or more
tables, and can include UNION statements and subqueries.
Each select_expr expression indicates a column or data that
you want to retrieve. You
must have at least one select expression. See Select
Expressions below.
The FROM clause indicates the table or tables from which to
retrieve rows.
Use either a single table name or a JOIN expression. See
JOIN
for details. If no table is involved, FROM DUAL can be
specified.
The PARTITION clause was introduced in MariaDB 10.0. See
Partition Pruning and Selection for details.
Each table can also be specified as db_name.tabl_name. Each
column can also be specified as tbl_name.col_name or even
db_name.tbl_name.col_name. This allows to write queries
which involve multiple databases. See Identifier Qualifiers
for syntax details.
The WHERE clause, if given, indicates the condition or
conditions that rows must satisfy to be selected.
where_condition is an expression that evaluates to true for
each row to be selected. The statement selects all rows if
there is no WHERE
clause.
In the WHERE clause, you can use any of the functions and
operators that MariaDB supports, except for aggregate
(summary) functions. See Functions and Operators and
Functions and Modifiers for use with GROUP BY (aggregate).
Use the ORDER BY clause to order the results.
Use the LIMIT clause allows you to restrict the results to
only
a certain number of rows, optionally with an offset.
Use the GROUP BY and HAVING clauses to group
rows together when they have columns or computed values in
common.
SELECT can also be used to retrieve rows computed without
reference to
any table.
Select Expressions
A SELECT statement must contain one or more select
expressions, separated
by commas. Each select expression can be one of the
following:
The name of a column.
Any expression using functions and operators.
* to select all columns from all tables in the FROM clause.
tbl_name.* to select all columns from just the table
tbl_name.
When specifying a column, you can either use just the column
name or qualify the column
name with the name of the table using tbl_name.col_name. The
qualified form is
useful if you are joining multiple tables in the FROM
clause. If you do not qualify the
column names when selecting from multiple tables, MariaDB
will try to find the column in
each table. It is an error if that column name exists in
multiple tables.
You can quote column names using backticks. If you are
qualifying column names
with table names, quote each part separately as
`tbl_name`.`col_name`.
If you use any grouping functions
in any of the select expressions, all rows in your results
will be implicitly grouped, as if
you had used GROUP BY NULL.
DISTINCT
A query may produce some identical rows. By default, all
rows are retrieved, even when their values are the same. To
explicitly specify that you want to retrieve identical rows,
use the ALL option. If you want duplicates to be removed
from the resultset, use the DISTINCT option. DISTINCTROW is
a synonym for DISTINCT. See also COUNT DISTINCT and SELECT
UNIQUE in Oracle mode.
INTO
The INTO clause is used to specify that the query results
should be written to a file or variable.
SELECT INTO OUTFILE - formatting and writing the result to
an external file.
SELECT INTO DUMPFILE - binary-safe writing of the
unformatted results to an external file.
SELECT INTO Variable - selecting and setting variables.
The reverse of SELECT INTO OUTFILE is LOAD DATA.
WAIT/NOWAIT
Set the lock wait timeout. See WAIT and NOWAIT.
PROCEDURE
Passes the whole result set to a C Procedure. See PROCEDURE
and PROCEDURE ANALYSE (the only built-in procedure not
requiring the server to be recompiled).
max_statement_time clause
By using max_statement_time in conjunction with SET
STATEMENT, it is possible to limit the execution time of
individual queries. For example:
SET STATEMENT max_statement_time=100 FOR
SELECT field1 FROM table_name ORDER BY field1;
URL: https://mariadb.com/kb/en/select/https://mariadb.com/kb/en/select/ �ngXi �� � �/ SELECT INTO DUMPFILESyntax
------
SELECT ... INTO DUMPFILE 'file_path'
Description
-----------
SELECT ... INTO DUMPFILE is a SELECT clause which writes the
resultset into a single unformatted row, without any
separators, in a file. The results will not be returned to
the client.
file_path can be an absolute path, or a relative path
starting from the data directory. It can only be specified
as a string literal, not as a variable. However, the
statement can be dynamically composed and executed as a
prepared statement to work around this limitation.
This statement is binary-safe and so is particularly useful
for writing BLOB values to file. It can be used, for
example, to copy an image or an audio document from the
database to a file. SELECT ... INTO FILE can be used to save
a text file.
The file must not exist. It cannot be overwritten. A user
needs the FILE privilege to run this statement. Also,
MariaDB needs permission to write files in the specified
location. If the secure_file_priv system variable is set to
a non-empty directory name, the file can only be written to
that directory.
Since MariaDB 5.1, the character_set_filesystem system
variable has controlled interpretation of file names that
are given as literal strings.
Example
SELECT _utf8'Hello world!' INTO DUMPFILE '/tmp/world';
SELECT LOAD_FILE('/tmp/world') AS world;
+--------------+
| world |
+--------------+
| Hello world! |
+--------------+
URL: https://mariadb.com/kb/en/select-into-dumpfile/https://mariadb.com/kb/en/select-into-dumpfile/ � S. SELECT INTO OUTFILESyntax
------
SELECT ... INTO OUTFILE 'file_name'
[CHARACTER SET charset_name]
[export_options]
export_options:
[{FIELDS | COLUMNS}
[TERMINATED BY 'string']
[[OPTIONALLY] ENCLOSED BY 'char']
[ESCAPED BY 'char']
]
[LINES
[STARTING BY 'string']
[TERMINATED BY 'string']
]
Description
-----------
SELECT INTO OUTFILE writes the resulting rows to a file, and
allows the use of column and row terminators to specify a
particular output format. The default is to terminate fields
with tabs (\t) and lines with newlines (\n).
The file must not exist. It cannot be overwritten. A user
needs the FILE privilege to run this statement. Also,
MariaDB needs permission to write files in the specified
location. If the secure_file_priv system variable is set to
a non-empty directory name, the file can only be written to
that directory.
The LOAD DATA INFILE statement complements SELECT INTO
OUTFILE.
Character-sets
The CHARACTER SET clause specifies the character set in
which the results are to be written. Without the clause, no
conversion takes place (the binary character set). In this
case, if there are multiple character sets, the output will
contain these too, and may not easily be able to be
reloaded.
In cases where you have two servers using different
character-sets, using SELECT INTO OUTFILE to transfer data
from one to the other can have unexpected results. To ensure
that MariaDB correctly interprets the escape sequences, use
the CHARACTER SET clause on both the SELECT INTO OUTFILE
statement and the subsequent LOAD DATA INFILE statement.
Example
The following example produces a file in the CSV format:
SELECT customer_id, firstname, surname INTO OUTFILE
'/exportdata/customers.txt'
FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
LINES TERMINATED BY '\n'
FROM customers;
URL: https://mariadb.com/kb/en/select-into-outfile/https://mariadb.com/kb/en/select-into-outfile/ � � WITHThe WITH keyword signifies a Common Table Expression (CTE).
It allows you to refer to a subquery expression many times
in a query, as if having a temporary table that only exists
for the duration of a query.
There are two kinds of CTEs:
Non-Recursive
Recursive
Common Table Expression WITH was introduced in MariaDB
10.2.1.
Recursive WITH has been supported since MariaDB 10.2.2.
Syntax
------
WITH [RECURSIVE] table_reference as (SELECT ...)
SELECT ...
You can use table_reference as any normal table in the
external SELECT part. You can also use WITH in sub queries.
WITH can also be used with EXPLAIN and SELECT.
Below is an example with the WITH at the top level:
WITH t AS (SELECT a FROM t1 WHERE b >= 'c')
SELECT * FROM t2, t WHERE t2.c = t.a;
The example below uses WITH in a subquery:
SELECT t1.a, t1.b FROM t1, t2
WHERE t1.a > t2.c
AND t2.c IN(WITH t AS (SELECT * FROM t1 WHERE t1.a
URL: https://mariadb.com/kb/en/with/https://mariadb.com/kb/en/with/ � ^# DESCRIBESyntax
------
{DESCRIBE | DESC} tbl_name [col_name | wild]
Description
-----------
DESCRIBE provides information about the columns in a table.
It is a shortcut for SHOW COLUMNS FROM.
These statements also display information for views.
col_name can be a column name, or a string containing the
SQL "%" and "_" wildcard characters to
obtain output only for the columns with names matching the
string. There is no
need to enclose the string within quotes unless it contains
spaces or other
special characters.
DESCRIBE city;
+------------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+----------+------+-----+---------+----------------+
| Id | int(11) | NO | PRI | NULL | auto_increment |
| Name | char(35) | YES | | NULL | |
| Country | char(3) | NO | UNI | | |
| District | char(20) | YES | MUL | | |
| Population | int(11) | YES | | NULL | |
+------------+----------+------+-----+---------+----------------+
The description for SHOW COLUMNS provides
more information about the output columns.
URL: https://mariadb.com/kb/en/describe/https://mariadb.com/kb/en/describe/ ���
�'� ��Ϋ �� � - SELECT WITH ROLLUPSyntax
------
See SELECT for the full syntax.
Description
-----------
The WITH ROLLUP modifier adds extra rows to the resultset
that represent super-aggregate summaries. The
super-aggregated column is represented by a NULL value.
Multiple aggregates over different columns will be added if
there are multiple GROUP BY columns.
The LIMIT clause can be used at the same time, and is
applied after the WITH ROLLUP rows have been added.
WITH ROLLUP cannot be used with ORDER BY. Some sorting is
still possible by using ASC or DESC clauses with the GROUP
BY column, although the super-aggregate rows will always be
added last.
Examples
--------
These examples use the following sample table
CREATE TABLE booksales (
country VARCHAR(35), genre
ENUM('fiction','non-fiction'), year YEAR, sales INT);
INSERT INTO booksales VALUES
('Senegal','fiction',2014,12234),
('Senegal','fiction',2015,15647),
('Senegal','non-fiction',2014,64980),
('Senegal','non-fiction',2015,78901),
('Paraguay','fiction',2014,87970),
('Paraguay','fiction',2015,76940),
('Paraguay','non-fiction',2014,8760),
('Paraguay','non-fiction',2015,9030);
The addition of the WITH ROLLUP modifier in this example
adds an extra row that aggregates both years:
SELECT year, SUM(sales) FROM booksales GROUP BY year;
+------+------------+
| year | SUM(sales) |
+------+------------+
| 2014 | 173944 |
| 2015 | 180518 |
+------+------------+
2 rows in set (0.08 sec)
SELECT year, SUM(sales) FROM booksales GROUP BY year WITH
ROLLUP;
+------+------------+
| year | SUM(sales) |
+------+------------+
| 2014 | 173944 |
| 2015 | 180518 |
| NULL | 354462 |
+------+------------+
In the following example, each time the genre, the year or
the country change, another super-aggregate row is added:
SELECT country, year, genre, SUM(sales)
FROM booksales GROUP BY country, year, genre;
+----------+------+-------------+------------+
| country | year | genre | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2014 | fiction | 87970 |
| Paraguay | 2014 | non-fiction | 8760 |
| Paraguay | 2015 | fiction | 76940 |
| Paraguay | 2015 | non-fiction | 9030 |
| Senegal | 2014 | fiction | 12234 |
| Senegal | 2014 | non-fiction | 64980 |
| Senegal | 2015 | fiction | 15647 |
| Senegal | 2015 | non-fiction | 78901 |
+----------+------+-------------+------------+
SELECT country, year, genre, SUM(sales)
FROM booksales GROUP BY country, year, genre WITH ROLLUP;
+----------+------+-------------+------------+
| country | year | genre | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2014 | fiction | 87970 |
| Paraguay | 2014 | non-fiction | 8760 |
| Paraguay | 2014 | NULL | 96730 |
| Paraguay | 2015 | fiction | 76940 |
| Paraguay | 2015 | non-fiction | 9030 |
| Paraguay | 2015 | NULL | 85970 |
| Paraguay | NULL | NULL | 182700 |
| Senegal | 2014 | fiction | 12234 |
| Senegal | 2014 | non-fiction | 64980 |
| Senegal | 2014 | NULL | 77214 |
| Senegal | 2015 | fiction | 15647 |
| Senegal | 2015 | non-fiction | 78901 |
| Senegal | 2015 | NULL | 94548 |
| Senegal | NULL | NULL | 171762 |
| NULL | NULL | NULL | 354462 |
+----------+------+-------------+------------+
The LIMIT clause, applied after WITH ROLLUP:
SELECT country, year, genre, SUM(sales)
FROM booksales GROUP BY country, year, genre WITH ROLLUP
LIMIT 4;
+----------+------+-------------+------------+
| country | year | genre | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2014 | fiction | 87970 |
| Paraguay | 2014 | non-fiction | 8760 |
| Paraguay | 2014 | NULL | 96730 |
| Paraguay | 2015 | fiction | 76940 |
+----------+------+-------------+------------+
Sorting by year descending:
SELECT country, year, genre, SUM(sales)
FROM booksales GROUP BY country, year DESC, genre WITH
ROLLUP;
+----------+------+-------------+------------+
| country | year | genre | SUM(sales) |
+----------+------+-------------+------------+
| Paraguay | 2015 | fiction | 76940 |
| Paraguay | 2015 | non-fiction | 9030 |
| Paraguay | 2015 | NULL | 85970 |
| Paraguay | 2014 | fiction | 87970 |
| Paraguay | 2014 | non-fiction | 8760 |
| Paraguay | 2014 | NULL | 96730 |
| Paraguay | NULL | NULL | 182700 |
| Senegal | 2015 | fiction | 15647 |
| Senegal | 2015 | non-fiction | 78901 |
| Senegal | 2015 | NULL | 94548 |
| Senegal | 2014 | fiction | 12234 |
| Senegal | 2014 | non-fiction | 64980 |
| Senegal | 2014 | NULL | 77214 |
| Senegal | NULL | NULL | 171762 |
| NULL | NULL | NULL | 354462 |
+----------+------+-------------+------------+
URL: https://mariadb.com/kb/en/select-with-rollup/https://mariadb.com/kb/en/select-with-rollup/ � �. ANALYZE FORMAT=JSONANALYZE FORMAT=JSON is a mix of the EXPLAIN FORMAT=JSON and
ANALYZE statement features. ANALYZE FORMAT=JSON $statement
will execute $statement, and then print the output of
EXPLAIN FORMAT=JSON, amended with the data from query
execution.
Basic Execution Data
You can get the following also from tabular ANALYZE
statement form:
r_rows is provided for any node that reads rows. It shows
how many rows were read, on average
r_filtered is provided whenever there is a condition that is
checked. It shows the percentage of rows left after checking
the condition.
Advanced Execution Data
The most important data that is not available in tabula
ANALYZE statement are:
r_loops field. This shows how many times the node was
executed. Most query plan elements have this field.
r_total_time_ms field. It shows how much time in total was
spent executing this node. If the node has subnodes, their
execution time is included.
r_buffer_size field. Query plan nodes that make use of
buffers report the size of buffer that was was used.
Data About Individual Query Plan Nodes
filesort node reports whether sorting was done with LIMIT n
parameter, and how many rows were in the sort result.
block-nl-join node has r_loops field, which allows to tell
whether Using join buffer was efficient
range-checked-for-each-record reports counters that show the
result of the check.
expression-cache is used for subqueries, and it reports how
many times the cache was used, and what cache hit ratio was.
union_result node has r_rows so one can see how many rows
were produced after UNION operation
and so forth
Use Cases
See Examples of ANALYZE FORMAT=JSON.
URL: https://mariadb.com/kb/en/analyze-format-json/https://mariadb.com/kb/en/analyze-format-json/ h \��߰ �� � , UNIONUNION is used to combine the results from multiple SELECT
statements into a single result set.
Syntax
------
SELECT ...
UNION [ALL | DISTINCT] SELECT ...
[UNION [ALL | DISTINCT] SELECT ...]
[ORDER BY [column [, column ...]]]
[LIMIT {[offset,] row_count | row_count OFFSET offset}]
Description
-----------
UNION is used to combine the results from multiple SELECT
statements into a single result set.
The column names from the first SELECT statement are used as
the column names for the results returned. Selected columns
listed in corresponding positions of each SELECT statement
should have the same data type. (For example, the first
column selected by the first statement should have the same
type as the first column selected by the other statements.)
If they don't, the type and length of the columns in the
result take into account the values returned by all of the
SELECTs, so there is no need for explicit casting. Note that
currently this is not the case for recursive CTEs - see
MDEV-12325.
Table names can be specified as db_name.tbl_name. This
permits writing UNIONs which involve multiple databases. See
Identifier Qualifiers for syntax details.
UNION queries cannot be used with aggregate functions.
ALL/DISTINCT
The ALL keyword causes duplicate rows to be preserved. The
DISTINCT keyword (the default if the keyword is omitted)
causes duplicate rows to be removed by the results.
UNION ALL and UNION DISTINCT can both be present in a query.
In this case, UNION DISTINCT will override any UNION ALLs to
its left.
Until MariaDB 10.1.1, all UNION ALL statements required the
server to create a temporary table. Since MariaDB 10.1.1,
the server can in most cases execute UNION ALL without
creating a temporary table, improving performance (see
MDEV-334).
ORDER BY and LIMIT
Individual SELECTs can contain their own ORDER BY and LIMIT
clauses. In this case, the individual queries need to be
wrapped between parentheses. However, this does not affect
the order of the UNION, so they only are useful to limit the
record read by one SELECT.
The UNION can have global ORDER BY and LIMIT clauses, which
affect the whole resultset. If the columns retrieved by
individual SELECT statements have an alias (AS), the ORDER
BY must use that alias, not the real column names.
HIGH_PRIORITY
Specifying a query as HIGH_PRIORITY will not work inside a
UNION. If applied to the first SELECT, it will be ignored.
Applying to a later SELECT results in a syntax error:
ERROR 1234 (42000): Incorrect usage/placement of
'HIGH_PRIORITY'
SELECT ... INTO ...
Individual SELECTs cannot be written INTO DUMPFILE or INTO
OUTFILE. If the last SELECT statement specifies INTO
DUMPFILE or INTO OUTFILE, the entire result of the UNION
will be written. Placing the clause after any other SELECT
will result in a syntax error.
If the result is a single row, SELECT ... INTO @var_name can
also be used.
Parentheses
From MariaDB 10.4.0, parentheses can be used to specify
precedence. Before this, a syntax error would be returned.
Examples
--------
UNION between tables having different column names:
(SELECT e_name AS name, email FROM employees)
UNION
(SELECT c_name AS name, email FROM customers);
Specifying the UNION's global order and limiting total
rows:
(SELECT name, email FROM employees)
UNION
(SELECT name, email FROM customers)
ORDER BY name LIMIT 10;
Adding a constant row:
(SELECT 'John Doe' AS name, 'john.doe@example.net' AS
email)
UNION
(SELECT name, email FROM customers);
Differing types:
SELECT CAST('x' AS CHAR(1)) UNION SELECT REPEAT('y',4);
+----------------------+
| CAST('x' AS CHAR(1)) |
+----------------------+
| x |
| yyyy |
+----------------------+
Returning the results in order of each individual SELECT by
use of a sort column:
(SELECT 1 AS sort_column, e_name AS name, email FROM
employees)
UNION
(SELECT 2, c_name AS name, email FROM customers) ORDER BY
sort_column;
Difference between UNION, EXCEPT and INTERSECT:
CREATE TABLE seqs (i INT);
INSERT INTO seqs VALUES (1),(2),(3),(4),(5),(6);
SELECT i FROM seqs WHERE i =3;
+------+
| i |
+------+
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
| 6 |
+------+
SELECT i FROM seqs WHERE i =3;
+------+
| i |
+------+
| 1 |
| 2 |
+------+
SELECT i FROM seqs WHERE i =3;
+------+
| i |
+------+
| 3 |
+------+
Parentheses for specifying precedence, from MariaDB 10.4.0
CREATE OR REPLACE TABLE t1 (a INT);
CREATE OR REPLACE TABLE t2 (b INT);
CREATE OR REPLACE TABLE t3 (c INT);
INSERT INTO t1 VALUES (1),(2),(3),(4);
INSERT INTO t2 VALUES (5),(6);
INSERT INTO t3 VALUES (1),(6);
((SELECT a FROM t1) UNION (SELECT b FROM t2)) INTERSECT
(SELECT c FROM t3);
+------+
| a |
+------+
| 1 |
| 6 |
+------+
(SELECT a FROM t1) UNION ((SELECT b FROM t2) INTERSECT
(SELECT c FROM t3));
+------+
| a |
+------+
| 1 |
| 2 |
| 3 |
| 4 |
| 6 |
+------+
URL: https://mariadb.com/kb/en/union/https://mariadb.com/kb/en/union/ _�H�n �s � �! UPDATESyntax
------
Single-table syntax:
UPDATE [LOW_PRIORITY] [IGNORE] table_reference
[PARTITION (partition_list)]
SET col1={expr1|DEFAULT} [,col2={expr2|DEFAULT}] ...
[WHERE where_condition]
[ORDER BY ...]
[LIMIT row_count]
Multiple-table syntax:
UPDATE [LOW_PRIORITY] [IGNORE] table_references
SET col1={expr1|DEFAULT} [, col2={expr2|DEFAULT}] ...
[WHERE where_condition]
Description
-----------
For the single-table syntax, the UPDATE statement updates
columns of existing rows in the named table with new values.
The
SET clause indicates which columns to modify and the values
they should be given. Each value can be given as an
expression, or the keyword
DEFAULT to set a column explicitly to its default value. The
WHERE clause, if given, specifies the conditions that
identify
which rows to update. With no WHERE clause, all rows are
updated. If the ORDER BY clause is specified, the rows are
updated in the order that is specified. The LIMIT clause
places a limit on the number of rows that can be updated.
The PARTITION clause was introduced in MariaDB 10.0. See
Partition Pruning and Selection for details.
Until MariaDB 10.3.2, for the multiple-table syntax, UPDATE
updates rows in each
table named in table_references that satisfy the conditions.
In this case,
ORDER BY and LIMIT cannot be used. This restriction was
lifted in MariaDB 10.3.2 and both clauses can be used with
multiple-table updates. An UPDATE can also reference tables
which are located in different databases; see Identifier
Qualifiers for the syntax.
where_condition is an expression that evaluates to true for
each row to be updated.
table_references and where_condition are as
specified as described in SELECT.
Assignments are evaluated in left-to-right order, unless the
SIMULTANEOUS_ASSIGNMENT sql_mode (available from MariaDB
10.3.5) is set, in which case the UPDATE statement evaluates
all assignments simultaneously.
You need the UPDATE privilege only for columns referenced in
an UPDATE that are actually updated. You need only the
SELECT privilege for any columns that are read but
not modified. See GRANT.
The UPDATE statement supports the following modifiers:
If you use the LOW_PRIORITY keyword, execution of
the UPDATE is delayed until no other clients are reading
from
the table. This affects only storage engines that use only
table-level
locking (MyISAM, MEMORY, MERGE). See HIGH_PRIORITY and
LOW_PRIORITY clauses for details.
If you use the IGNORE keyword, the update statement does
not abort even if errors occur during the update. Rows for
which
duplicate-key conflicts occur are not updated. Rows for
which columns are
updated to values that would cause data conversion errors
are updated to the
closest valid values instead.
UPDATE Statements With the Same Source and Target
From MariaDB 10.3.2, UPDATE statements may have the same
source and target.
For example, given the following table:
DROP TABLE t1;
CREATE TABLE t1 (c1 INT, c2 INT);
INSERT INTO t1 VALUES (10,10), (20,20);
Until MariaDB 10.3.1, the following UPDATE statement would
not work:
UPDATE t1 SET c1=c1+1 WHERE c2=(SELECT MAX(c2) FROM t1);
ERROR 1093 (HY000): Table 't1' is specified twice,
both as a target for 'UPDATE' and as a separate source
for data
From MariaDB 10.3.2, the statement executes successfully:
UPDATE t1 SET c1=c1+1 WHERE c2=(SELECT MAX(c2) FROM t1);
SELECT * FROM t1;
+------+------+
| c1 | c2 |
+------+------+
| 10 | 10 |
| 21 | 20 |
+------+------+
Example
Single-table syntax:
UPDATE table_name SET column1 = value1, column2 = value2
WHERE id=100;
Multiple-table syntax:
UPDATE tab1, tab2 SET tab1.column1 = value1, tab1.column2 =
value2 WHERE tab1.id = tab2.id;
URL: https://mariadb.com/kb/en/update/https://mariadb.com/kb/en/update/ � (6 ANALYZE FORMAT=JSON ExamplesExample #1
Customers who have ordered more than 1M goods.
ANALYZE FORMAT=JSON
SELECT CONT(*)
FROM customer
WHERE
(SELECT SUM(o_totalprice) FROM orders WHERE
o_custkey=c_custkey) > 1000*1000;
The query takes 40 seconds over cold cache
EXPLAIN: {
"query_block": {
"select_id": 1,
"r_loops": 1,
"r_total_time_ms": 39872,
"table": {
"table_name": "customer",
"access_type": "index",
"key": "i_c_nationkey",
"key_length": "5",
"used_key_parts": ["c_nationkey"],
"r_loops": 1,
"rows": 150303,
"r_rows": 150000,
"r_total_time_ms": 270.3,
"filtered": 100,
"r_filtered": 60.691,
"attached_condition": "((subquery#2) > ((1000 *
1000)))",
"using_index": true
},
"subqueries": [
{
"query_block": {
"select_id": 2,
"r_loops": 150000,
"r_total_time_ms": 39531,
"table": {
"table_name": "orders",
"access_type": "ref",
"possible_keys": ["i_o_custkey"],
"key": "i_o_custkey",
"key_length": "5",
"used_key_parts": ["o_custkey"],
"ref": ["dbt3sf1.customer.c_custkey"],
"r_loops": 150000,
"rows": 7,
"r_rows": 10,
"r_total_time_ms": 39208,
"filtered": 100,
"r_filtered": 100
}
}
}
]
}
}
ANALYZE shows that 39.2 seconds were spent in the subquery,
which was executed 150K times (for every row of outer
table).
URL: https://mariadb.com/kb/en/analyze-formatjson-examples/https://mariadb.com/kb/en/analyze-formatjson-examples/ �� �`��� �� � !, ANALYZE StatementThe ANALYZE statement was introduced in MariaDB 10.1.0.
Description
-----------
The ANALYZE statement is similar to the EXPLAIN statement.
ANALYZE statement will invoke the optimizer, execute the
statement, and then produce EXPLAIN output instead of the
result set. The EXPLAIN output will be annotated with
statistics from statement execution.
This lets one check how close the optimizer's estimates
about the query plan are to the reality. ANALYZE produces an
overview, while the
ANALYZE FORMAT=JSON command provides a more detailed view of
the query plan and the query execution.
The syntax is
ANALYZE explainable_statement;
where the statement is any statement for which one can run
EXPLAIN.
Command Output
Consider an example:
ANALYZE SELECT * FROM tbl1
WHERE key1
BETWEEN 10 AND 200 AND
col1 LIKE 'foo%'\G
*************************** 1. row
***************************
id: 1
select_type: SIMPLE
table: tbl1
type: range
possible_keys: key1
key: key1
key_len: 5
ref: NULL
rows: 181
r_rows: 181
filtered: 100.00
r_filtered: 10.50
Extra: Using index condition; Using where
Compared to EXPLAIN, ANALYZE produces two extra columns:
r_rows is an observation-based counterpart of the rows
column. It shows how many rows were actually read from the
table.
r_filtered is an observation-based counterpart of the
filtered column. It shows which fraction of rows was left
after applying the WHERE condition.
Interpreting the Output
Joins
Let's consider a more complicated example.
ANALYZE SELECT *
FROM orders, customer
WHERE
customer.c_custkey=orders.o_custkey AND
customer.c_acctbal 200*1000
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+
| id | select_type | table | type | possible_keys | key |
key_len | ref | rows | r_rows | filtered | r_filtered |
Extra |
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+
| 1 | SIMPLE | customer | ALL | PRIMARY,... | NULL | NULL |
NULL | 149095 | 150000 | 18.08 | 9.13 | Using where |
| 1 | SIMPLE | orders | ref | i_o_custkey | i_o_custkey | 5
| customer.c_custkey | 7 | 10 | 100.00 | 30.03 | Using where
|
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+
Here, one can see that
For table customer, customer.rows=149095,
customer.r_rows=150000. The estimate for number of rows we
will read was fairly precise
customer.filtered=18.08, customer.r_filtered=9.13. The
optimizer somewhat overestimated the number of records that
will match selectivity of condition attached to `customer`
table (in general, when you have a full scan and r_filtered
is less than 15%, it's time to consider adding an
appropriate index).
For table orders, orders.rows=7, orders.r_rows=10. This
means that on average, there are 7 orders for a given
c_custkey, but in our case there were 10, which is close to
the expectation (when this number is consistently far from
the expectation, it may be time to run ANALYZE TABLE, or
even edit the table statistics manually to get better query
plans).
orders.filtered=100, orders.r_filtered=30.03. The optimizer
didn't have any way to estimate which fraction of records
will be left after it checks the condition that is attached
to table orders (it's orders.o_totalprice > 200*1000). So,
it used 100%. In reality, it is 30%. 30% is typically not
selective enough to warrant adding new indexes. For joins
with many tables, it might be worth to collect and use
column statistics for columns in question, this may help the
optimizer to pick a better query plan.
Meaning of NULL in r_rows and r_filtered
Let's modify the previous example slightly
ANALYZE SELECT *
FROM orders, customer
WHERE
customer.c_custkey=orders.o_custkey AND
customer.c_acctbal 200*1000;
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+
| id | select_type | table | type | possible_keys | key |
key_len | ref | rows | r_rows | filtered | r_filtered |
Extra |
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+
| 1 | SIMPLE | customer | ALL | PRIMARY,... | NULL | NULL |
NULL | 149095 | 150000 | 18.08 | 0.00 | Using where |
| 1 | SIMPLE | orders | ref | i_o_custkey | i_o_custkey | 5
| customer.c_custkey | 7 | NULL | 100.00 | NULL | Using
where |
+----+-------------+----------+------+---------------+-------------+---------+--------------------+--------+--------+----------+------------+-------------+
Here, one can see that orders.r_rows=NULL and
orders.r_filtered=NULL. This means that table orders was not
scanned even once.
Indeed, we can also see customer.r_filtered=0.00. This shows
that a part of WHERE attached to table `customer` was never
satisfied (or, satisfied in less than 0.01% of cases).
ANALYZE FORMAT=JSON
ANALYZE FORMAT=JSON produces JSON output. It produces much
more information than tabular ANALYZE.
Notes
ANALYZE UPDATE or ANALYZE DELETE will actually make
updates/deletes (ANALYZE SELECT will perform the select
operation and then discard the resultset).
PostgreSQL has a similar command, EXPLAIN ANALYZE.
The EXPLAIN in the slow query log feature allows MariaDB to
have ANALYZE output of slow queries printed into the slow
query log (see MDEV-6388).
URL: https://mariadb.com/kb/en/analyze-statement/https://mariadb.com/kb/en/analyze-statement/ l�-� Syntax
------
EXPLAIN tbl_name
Or
EXPLAIN [EXTENDED | PARTITIONS]
{SELECT select_options | UPDATE update_options | DELETE
delete_options}
Description
-----------
The EXPLAIN statement can be used either as a synonym for
DESCRIBE or as a way to obtain information about how MariaDB
executes a SELECT (as well as UPDATE and DELETE since
MariaDB 10.0.5) statement:
'EXPLAIN tbl_name' is synonymous with
'DESCRIBE tbl_name' or
'SHOW COLUMNS FROM tbl_name'.
When you precede a SELECT statement (or, since MariaDB
10.0.5, an UPDATE or a DELETE as well) with the keyword
EXPLAIN, MariaDB displays information from the optimizer
about the query execution plan. That is, MariaDB explains
how it would
process the SELECT, UPDATE or DELETE, including information
about how tables
are joined and in which order. EXPLAIN EXTENDED can be
used to provide additional information.
EXPLAIN PARTITIONS has been available since MySQL 5.1.5. It
is useful only when examining queries involving partitioned
tables. For details, see Partition pruning and selection.
ANALYZE statement, which performs the query as well as
producing EXPLAIN output, and provides actual as well as
estimated statistics, has been available from MariaDB
10.1.0.
Since MariaDB 10.0.5, it has been possible to have EXPLAIN
output printed in the slow query log. See EXPLAIN in the
Slow Query Log for details.
Since MariaDB 10.0, SHOW EXPLAIN shows the output of a
running statement. In some cases, its output can be closer
to reality than EXPLAIN.
Since MariaDB 10.1, the ANALYZE statement runs a statement
and returns information about its execution plan. It also
shows additional columns, to check how much the optimizer's
estimation about filtering and found rows are close to
reality.
There is an online EXPLAIN Analyzer that you can use to
share EXPLAIN and EXPLAIN EXTENDED output with others.
EXPLAIN can acquire metadata locks in the same way that
SELECT does, as it needs to know table metadata and,
sometimes, data as well.
The columns in EXPLAIN ... SELECT
Column name | Description |
id | Sequence number that shows in which order tables are
joined. |
select_type | What kind of SELECT the table comes from. |
table | Alias name of table. Materialized temporary tables
for sub queries are named |
type | How rows are found from the table (join type). |
possible_keys | keys in table that could be used to find
rows in the table |
key | The name of the key that is used to retrieve rows.
NULL is no key was used. |
key_len | How many bytes of the key that was used (shows if
we are using only parts of the multi-column key). |
ref | The reference that is used to as the key value. |
rows | An estimate of how many rows we will find in the
table for each key lookup. |
Extra | Extra information about this join. |
Here are descriptions of the values for some of the more
complex columns in EXPLAIN ... SELECT:
"select_type" column
The select_type column can have the following values:
Value | Description |
DEPENDENT SUBQUERY | The SUBQUERY is DEPENDENT. |
DEPENDENT UNION | The UNION is DEPENDENT. |
DERIVED | The SELECT is DERIVED from the PRIMARY. |
MATERIALIZED | The SUBQUERY is MATERIALIZED. |
PRIMARY | The SELECT is a PRIMARY one. |
SIMPLE | The SELECT is a SIMPLE one. |
SUBQUERY | The SELECT is a SUBQUERY of the PRIMARY. |
UNCACHEABLE SUBQUERY | The SUBQUERY is UNCACHEABLE. |
UNCACHEABLE UNION | The UNION is UNCACHEABLE. |
UNION | The SELECT is a UNION of the PRIMARY. |
UNION RESULT | The result of the UNION. |
"Type" column
This column contains information on how the table is
accessed.
Value | Description |
ALL | A full table scan is done for the table (all rows are
read). This is bad if the table is large and the table is
joined against a previous table! This happens when the
optimizer could not find any usable index to access rows. |
const | There is only one possibly matching row in the
table. The row is read before the optimization phase and all
columns in the table are treated as constants. |
eq_ref | A unique index is used to find the rows. This is
the best possible plan to find the row. |
fulltext | A fulltext index is used to access the rows. |
index_merge | A 'range' access is done for for several
index and the found rows are merged. The key column shows
which keys are used. |
index_subquery | This is similar as ref, but used for sub
queries that are transformed to key lookups. |
index | A full scan over the used index. Better than ALL but
still bad if index is large and the table is joined against
a previous table. |
range | The table will be accessed with a key over one or
more value ranges. |
ref_or_null | Like 'ref' but in addition another search
for the 'null' value is done if the first value was not
found. This happens usually with sub queries. |
ref | A non unique index or prefix of an unique index is
used to find the rows. Good if the prefix doesn't match
many rows. |
system | The table has 0 or 1 rows. |
unique_subquery | This is similar as eq_ref, but used for
sub queries that are transformed to key lookups |
"Extra" column
This column consists of one or more of the following values,
separated by ';'
Note that some of these values are detected after the
optimization phase.
The optimization phase can do the following changes to the
WHERE clause:
Add the expressions from the ON and USING clauses to the
WHERE
clause.
Constant propagation: If there is column=constant, replace
all column
instances with this constant.
Replace all columns from 'const' tables with their values.
Remove the used key columns from the WHERE (as this will be
tested as
part of the key lookup).
Remove impossible constant sub expressions.
For example WHERE '(a=1 and a=2) OR b=1' becomes 'b=1'.
Replace columns with other columns that has identical
values:
Example: WHERE a=b and a=c may be treated
as 'WHERE a=b and a=c and b=c'.
Add extra conditions to detect impossible row conditions
earlier. This
happens mainly with OUTER JOIN where we in some cases add
detection
of NULL values in the WHERE (Part of 'Not exists'
optimization).
This can cause an unexpected 'Using where' in the Extra
column.
For each table level we remove expressions that have already
been tested when
we read the previous row. Example: When joining tables t1
with t2
using the following WHERE 't1.a=1 and t1.a=t2.b', we
don't have to
test 't1.a=1' when checking rows in t2 as we already know
that this
expression is true.
Value | Description |
const row not found | The table was a system table (a table
with should exactly one row), but no row was found. |
Distinct | If distinct optimization (remove duplicates) was
used. This is marked only for the last table in the SELECT.
|
Full scan on NULL key | The table is a part of the sub query
and if the value that is used to match the sub query will be
NULL, we will do a full table scan. |
Impossible HAVING | The used HAVING clause is always false
so the SELECT will return no rows. |
Impossible WHERE noticed after reading const tables. | The
used WHERE clause is always false so the SELECT will return
no rows. This case was detected after we had read all
'const' tables and used the column values as constant in
the WHERE clause. For example: WHERE const_column=5 and
const_column had a value of 4. |
Impossible WHERE | The used WHERE clause is always false so
the SELECT will return no rows. For example: WHERE 1=2 |
No matching min/max row | During early optimization of
MIN()/MAX() values it was detected that no row could match
the WHERE clause. The MIN()/MAX() function will return NULL.
|
no matching row in const table | The table was a const table
(a table with only one possible matching row), but no row
was found. |
No tables used | The SELECT was a sub query that did not use
any tables. For example a there was no FROM clause or a FROM
DUAL clause. |
Not exists | Stop searching after more row if we find one
single matching row. This optimization is used with LEFT
JOIN where one is explicitly searching for rows that
doesn't e�ŀ� xists in the LEFT JOIN TABLE. Example: SELECT *
FROM t1 LEFT JOIN t2 on (...) WHERE t2.not_null_column IS
NULL. As t2.not_null_column can only be NULL if there was no
matching row for on condition, we can stop searching if we
find a single matching row. |
Open_frm_only | For information_schema tables. Only the frm
(table definition file was opened) was opened for each
matching row. |
Open_full_table | For information_schema tables. A full
table open for each matching row is done to retrieve the
requested information. (Slow) |
Open_trigger_only | For information_schema tables. Only the
trigger file definition was opened for each matching row. |
Range checked for each record (index map: ...) | This only
happens when there was no good default index to use but
there may some index that could be used when we can treat
all columns from previous table as constants. For each row
combination the optimizer will decide which index to use (if
any) to fetch a row from this table. This is not fast, but
faster than a full table scan that is the only other choice.
The index map is a bitmask that shows which index are
considered for each row condition. |
Scanned 0/1/all databases | For information_schema tables.
Shows how many times we had to do a directory scan. |
Select tables optimized away | All tables in the join was
optimized away. This happens when we are only using
COUNT(*), MIN() and MAX() functions in the SELECT and we
where able to replace all of these with constants. |
Skip_open_table | For information_schema tables. The queried
table didn't need to be opened. |
unique row not found | The table was detected to be a const
table (a table with only one possible matching row) during
the early optimization phase, but no row was found. |
Using filesort | Filesort is needed to resolve the query.
This means an extra phase where we first collect all columns
to sort, sort them with a disk based merge sort and then use
the sorted set to retrieve the rows in sorted order. If the
column set is small, we store all the columns in the sort
file to not have to go to the database to retrieve them
again. |
Using index | Only the index is used to retrieve the needed
information from the table. There is no need to perform an
extra seek to retrieve the actual record. |
Using index condition | Like 'Using where' but the where
condition is pushed down to the table engine for internal
optimization at the index level. |
Using index condition(BKA) | Like 'Using index condition'
but in addition we use batch key access to retrieve rows. |
Using index for group-by | The index is being used to
resolve a GROUP BY or DISTINCT query. The rows are not read.
This is very efficient if the table has a lot of identical
index entries as duplicates are quickly jumped over. |
Using intersect(...) | For index_merge joins. Shows which
index are part of the intersect. |
Using join buffer | We store previous row combinations in a
row buffer to be able to match each row against all of the
rows combinations in the join buffer at one go. |
Using sort_union(...) | For index_merge joins. Shows which
index are part of the union. |
Using temporary | A temporary table is created to hold the
result. This typically happens if you are using GROUP BY,
DISTINCT or ORDER BY. |
Using where | A WHERE expression (in additional to the
possible key lookup) is used to check if the row should be
accepted. If you don't have 'Using where' together with a
join type of ALL, you are probably doing something wrong! |
Using where with pushed condition | Like 'Using where' but
the where condition is pushed down to the table engine for
internal optimization at the row level. |
Using buffer | The UPDATE statement will first buffer the
rows, and then run the updates, rather than do updates on
the fly. See Using Buffer UPDATE Algorithm for a detailed
explanation. |
EXPLAIN EXTENDED
The EXTENDED keyword adds another column, filtered, to the
output. This is a percentage estimate of the table rows that
will be filtered by the condition.
An EXPLAIN EXTENDED will always throw a warning, as it adds
extra Message information to a subsequent SHOW WARNINGS
statement. This includes what the SELECT query would look
like after optimizing and rewriting rules are applied and
how the optimizer qualifies columns and tables.
Examples
--------
As synonym for DESCRIBE or SHOW COLUMNS FROM:
DESCRIBE city;
+------------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+----------+------+-----+---------+----------------+
| Id | int(11) | NO | PRI | NULL | auto_increment |
| Name | char(35) | YES | | NULL | |
| Country | char(3) | NO | UNI | | |
| District | char(20) | YES | MUL | | |
| Population | int(11) | YES | | NULL | |
+------------+----------+------+-----+---------+----------------+
A simple set of examples to see how EXPLAIN can identify
poor index usage:
CREATE TABLE IF NOT EXISTS `employees_example` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`first_name` varchar(30) NOT NULL,
`last_name` varchar(40) NOT NULL,
`position` varchar(25) NOT NULL,
`home_address` varchar(50) NOT NULL,
`home_phone` varchar(12) NOT NULL,
`employee_code` varchar(25) NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `employee_code` (`employee_code`),
KEY `first_name` (`first_name`,`last_name`)
) ENGINE=Aria;
INSERT INTO `employees_example` (`first_name`, `last_name`,
`position`, `home_address`, `home_phone`, `employee_code`)
VALUES
('Mustapha', 'Mond', 'Chief Executive Officer', '692
Promiscuous Plaza', '326-555-3492', 'MM1'),
('Henry', 'Foster', 'Store Manager', '314 Savage
Circle', '326-555-3847', 'HF1'),
('Bernard', 'Marx', 'Cashier', '1240 Ambient
Avenue', '326-555-8456', 'BM1'),
('Lenina', 'Crowne', 'Cashier', '281 Bumblepuppy
Boulevard', '328-555-2349', 'LC1'),
('Fanny', 'Crowne', 'Restocker', '1023 Bokanovsky
Lane', '326-555-6329', 'FC1'),
('Helmholtz', 'Watson', 'Janitor', '944 Soma
Court', '329-555-2478', 'HW1');
SHOW INDEXES FROM employees_example;
+-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name
| Collation | Cardinality | Sub_part | Packed | Null |
Index_type | Comment | Index_comment |
+-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| employees_example | 0 | PRIMARY | 1 | id | A | 7 | NULL |
NULL | | BTREE | | |
| employees_example | 0 | employee_code | 1 | employee_code
| A | 7 | NULL | NULL | | BTREE | | |
| employees_example | 1 | first_name | 1 | first_name | A |
NULL | NULL | NULL | | BTREE | | |
| employees_example | 1 | first_name | 2 | last_name | A |
NULL | NULL | NULL | | BTREE | | |
+-------------------+------------+---------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
SELECT on a primary key:
EXPLAIN SELECT * FROM employees_example WHERE id=1;
+------+-------------+-------------------+-------+---------------+---------+---------+-------+------+-------+
| id | select_type | table | type | possible_keys | key |
key_len | ref | rows | Extra |
+------+-------------+-------------------+-------+---------------+---------+---------+-------+------+-------+
| 1 | SIMPLE | employees_example | const | PRIMARY | PRIMARY
| 4 | const | 1 | |
+------+-------------+-------------------+-------+---------------+---------+---------+-------+------+-------+
The type is const, which means that only one possible result
could be returned.
Now, returning the same record but searching by their phone
number:
EXPLAIN SELECT * FROM employees_example WHERE
home_phone='326-555-3492';
+------+-------------+-------------------+------+---------------+------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys | key |
key_len | ref | rows | Extra |
+------+-------------+ �K �U
� b. EXPLAIN FORMAT=JSONStarting from version 10.1.2, MariaDB supports the EXPLAIN
FORMAT=JSON syntax.
Synopsis
EXPLAIN FORMAT=JSON is a variant of EXPLAIN command that
produces output in JSON form. The output always has one row
which has only one column titled "JSON". The contents are
a JSON representation of the query plan, formatted for
readability:
EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE col1=1\G
*************************** 1. row
***************************
EXPLAIN: {
"query_block": {
"select_id": 1,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 1000,
"filtered": 100,
"attached_condition": "(t1.col1 = 1)"
}
}
}
Output is different from MySQL
The output of MariaDB's EXPLAIN FORMAT=JSON is different
from EXPLAIN FORMAT=JSON in MySQL.The reasons for that are:
MySQL's output has deficiencies. Some are listed here:
EXPLAIN FORMAT=JSON in MySQL)
The output of MySQL's EXPLAIN FORMAT=JSON is not defined.
Even MySQL Workbench has trouble parsing it (see this blog
post).
MariaDB has query optimizations that MySQL does not have.
Ergo, MariaDB generates query plans that MySQL does not
generate.
A (as yet incomplete) list of how MariaDB's output is
different from MySQL can be found here: EXPLAIN FORMAT=JSON
differences from MySQL.
Output format
TODO: MariaDB's output format description.
URL: https://mariadb.com/kb/en/explain-format-json/https://mariadb.com/kb/en/explain-format-json/ � c& ST_CONTAINSSyntax
------
ST_CONTAINS(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether a geometry g1 completely
contains geometry g2.
ST_CONTAINS() uses object shapes, while CONTAINS(), based on
the original MySQL implementation, uses object bounding
rectangles.
ST_CONTAINS tests the opposite relationship to ST_WITHIN().
Examples
--------
SET @g1 = ST_GEOMFROMTEXT('POLYGON((175 150, 20 40, 50 60,
125 100, 175 150))');
SET @g2 = ST_GEOMFROMTEXT('POINT(174 149)');
SELECT ST_CONTAINS(@g1,@g2);
+----------------------+
| ST_CONTAINS(@g1,@g2) |
+----------------------+
| 1 |
+----------------------+
SET @g2 = ST_GEOMFROMTEXT('POINT(175 151)');
SELECT ST_CONTAINS(@g1,@g2);
+----------------------+
| ST_CONTAINS(@g1,@g2) |
+----------------------+
| 0 |
+----------------------+
URL: https://mariadb.com/kb/en/st-contains/https://mariadb.com/kb/en/st-contains/ �
�% ST_CROSSESSyntax
------
ST_CROSSES(g1,g2)
Description
-----------
Returns 1 if geometry g1 spatially crosses geometry g2.
Returns NULL if g1 is a Polygon or a MultiPolygon, or if g2
is a
Point or a MultiPoint. Otherwise, returns 0.
The term spatially crosses denotes a spatial relation
between two
given geometries that has the following properties:
The two geometries intersect
Their intersection results in a geometry that has a
dimension that is one
less than the maximum dimension of the two given geometries
Their intersection is not equal to either of the two given
geometries
ST_CROSSES() uses object shapes, while CROSSES(), based on
the original MySQL implementation, uses object bounding
rectangles.
Examples
--------
SET @g1 = ST_GEOMFROMTEXT('LINESTRING(174 149, 176 151)');
SET @g2 = ST_GEOMFROMTEXT('POLYGON((175 150, 20 40, 50 60,
125 100, 175 150))');
SELECT ST_CROSSES(@g1,@g2);
+---------------------+
| ST_CROSSES(@g1,@g2) |
+---------------------+
| 1 |
+---------------------+
SET @g1 = ST_GEOMFROMTEXT('LINESTRING(176 149, 176 151)');
SELECT ST_CROSSES(@g1,@g2);
+---------------------+
| ST_CROSSES(@g1,@g2) |
+---------------------+
| 0 |
+---------------------+
URL: https://mariadb.com/kb/en/st-crosses/https://mariadb.com/kb/en/st-crosses/ � l& ST_DISJOINTSyntax
------
ST_DISJOINT(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether geometry g1 is spatially
disjoint from
(does not intersect with) geometry g2.
ST_DISJOINT() uses object shapes, while DISJOINT(), based on
the original MySQL implementation, uses object bounding
rectangles.
ST_DISJOINT() tests the opposite relationship to
ST_INTERSECTS().
Examples
--------
SET @g1 = ST_GEOMFROMTEXT('POINT(0 0)');
SET @g2 = ST_GEOMFROMTEXT('LINESTRING(2 0, 0 2)');
SELECT ST_DISJOINT(@g1,@g2);
+----------------------+
| ST_DISJOINT(@g1,@g2) |
+----------------------+
| 1 |
+----------------------+
SET @g2 = ST_GEOMFROMTEXT('LINESTRING(0 0, 0 2)');
SELECT ST_DISJOINT(@g1,@g2);
+----------------------+
| ST_DISJOINT(@g1,@g2) |
+----------------------+
| 0 |
+----------------------+
URL: https://mariadb.com/kb/en/st_disjoint/https://mariadb.com/kb/en/st_disjoint/ � ($ ST_EQUALSSyntax
------
ST_EQUALS(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether geometry g1 is spatially
equal to geometry g2.
ST_EQUALS() uses object shapes, while EQUALS(), based on the
original MySQL implementation, uses object bounding
rectangles.
Examples
--------
SET @g1 = ST_GEOMFROMTEXT('LINESTRING(174 149, 176 151)');
SET @g2 = ST_GEOMFROMTEXT('LINESTRING(176 151, 174 149)');
SELECT ST_EQUALS(@g1,@g2);
+--------------------+
| ST_EQUALS(@g1,@g2) |
+--------------------+
| 1 |
+--------------------+
SET @g1 = ST_GEOMFROMTEXT('POINT(0 2)');
SET @g1 = ST_GEOMFROMTEXT('POINT(2 0)');
SELECT ST_EQUALS(@g1,@g2);
+--------------------+
| ST_EQUALS(@g1,@g2) |
+--------------------+
| 0 |
+--------------------+
URL: https://mariadb.com/kb/en/st-equals/https://mariadb.com/kb/en/st-equals/ 0c��_ &�� ��S*� � �
h( ST_INTERSECTSSyntax
------
ST_INTERSECTS(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether geometry g1 spatially
intersects geometry g2.
ST_INTERSECTS() uses object shapes, while INTERSECTS(),
based on the original MySQL implementation, uses object
bounding rectangles.
ST_INTERSECTS() tests the opposite relationship to
ST_DISJOINT().
Examples
--------
SET @g1 = ST_GEOMFROMTEXT('POINT(0 0)');
SET @g2 = ST_GEOMFROMTEXT('LINESTRING(0 0, 0 2)');
SELECT ST_INTERSECTS(@g1,@g2);
+------------------------+
| ST_INTERSECTS(@g1,@g2) |
+------------------------+
| 1 |
+------------------------+
SET @g2 = ST_GEOMFROMTEXT('LINESTRING(2 0, 0 2)');
SELECT ST_INTERSECTS(@g1,@g2);
+------------------------+
| ST_INTERSECTS(@g1,@g2) |
+------------------------+
| 0 |
+------------------------+
URL: https://mariadb.com/kb/en/st-intersects/https://mariadb.com/kb/en/st-intersects/ �
�% ST_TOUCHESSyntax
------
ST_TOUCHES(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether geometry g1 spatially
touches geometry g2. Two geometries spatially touch if the
interiors of the geometries do not intersect,
but the boundary of one of the geometries intersects either
the boundary or the
interior of the other.
ST_TOUCHES() uses object shapes, while TOUCHES(), based on
the original MySQL implementation, uses object bounding
rectangles.
Examples
--------
SET @g1 = ST_GEOMFROMTEXT('POINT(2 0)');
SET @g2 = ST_GEOMFROMTEXT('LINESTRING(2 0, 0 2)');
SELECT ST_TOUCHES(@g1,@g2);
+---------------------+
| ST_TOUCHES(@g1,@g2) |
+---------------------+
| 1 |
+---------------------+
SET @g1 = ST_GEOMFROMTEXT('POINT(2 1)');
SELECT ST_TOUCHES(@g1,@g2);
+---------------------+
| ST_TOUCHES(@g1,@g2) |
+---------------------+
| 0 |
+---------------------+
URL: https://mariadb.com/kb/en/st-touches/https://mariadb.com/kb/en/st-touches/ � @$ ST_WITHINSyntax
------
ST_WITHIN(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether geometry g1 is spatially
within geometry g2.
This tests the opposite relationship as ST_CONTAINS().
ST_WITHIN() uses object shapes, while WITHIN(), based on the
original MySQL implementation, uses object bounding
rectangles.
Examples
--------
SET @g1 = ST_GEOMFROMTEXT('POINT(174 149)');
SET @g2 = ST_GEOMFROMTEXT('POLYGON((175 150, 20 40, 50 60,
125 100, 175 150))');
SELECT ST_WITHIN(@g1,@g2);
+--------------------+
| ST_WITHIN(@g1,@g2) |
+--------------------+
| 1 |
+--------------------+
SET @g1 = ST_GEOMFROMTEXT('POINT(176 151)');
SELECT ST_WITHIN(@g1,@g2);
+--------------------+
| ST_WITHIN(@g1,@g2) |
+--------------------+
| 0 |
+--------------------+
URL: https://mariadb.com/kb/en/st-within/https://mariadb.com/kb/en/st-within/ � �! WITHINSyntax
------
Within(g1,g2)
Description
-----------
Returns 1 or 0 to indicate whether g1 is spatially within
g2.
This tests the opposite relationship as Contains().
WITHIN() is based on the original MySQL implementation, and
uses object bounding rectangles, while ST_WITHIN() uses
object shapes.
Examples
--------
SET @g1 = GEOMFROMTEXT('POINT(174 149)');
SET @g2 = GEOMFROMTEXT('POINT(176 151)');
SET @g3 = GEOMFROMTEXT('POLYGON((175 150, 20 40, 50 60, 125
100, 175 150))');
SELECT within(@g1,@g3);
+-----------------+
| within(@g1,@g3) |
+-----------------+
| 1 |
+-----------------+
SELECT within(@g2,@g3);
+-----------------+
| within(@g2,@g3) |
+-----------------+
| 0 |
+-----------------+
URL: https://mariadb.com/kb/en/within/https://mariadb.com/kb/en/within/ � a " ADDDATESyntax
------
ADDDATE(date,INTERVAL expr unit), ADDDATE(expr,days)
Description
-----------
When invoked with the INTERVAL form of the second argument,
ADDDATE()
is a synonym for DATE_ADD(). The related function
SUBDATE() is a synonym for DATE_SUB(). For
information on the INTERVAL unit argument, see the
discussion for
DATE_ADD().
When invoked with the days form of the second argument,
MariaDB treats it as an
integer number of days to be added to expr.
Examples
--------
SELECT DATE_ADD('2008-01-02', INTERVAL 31 DAY);
+-----------------------------------------+
| DATE_ADD('2008-01-02', INTERVAL 31 DAY) |
+-----------------------------------------+
| 2008-02-02 |
+-----------------------------------------+
SELECT ADDDATE('2008-01-02', INTERVAL 31 DAY);
+----------------------------------------+
| ADDDATE('2008-01-02', INTERVAL 31 DAY) |
+----------------------------------------+
| 2008-02-02 |
+----------------------------------------+
SELECT ADDDATE('2008-01-02', 31);
+---------------------------+
| ADDDATE('2008-01-02', 31) |
+---------------------------+
| 2008-02-02 |
+---------------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
("2007-01-30 21:31:07"),
("1983-10-15 06:42:51"),
("2011-04-21 12:34:56"),
("2011-10-30 06:31:41"),
("2011-01-30 14:03:25"),
("2004-10-07 11:19:34");
SELECT d, ADDDATE(d, 10) from t1;
+---------------------+---------------------+
| d | ADDDATE(d, 10) |
+---------------------+---------------------+
| 2007-01-30 21:31:07 | 2007-02-09 21:31:07 |
| 1983-10-15 06:42:51 | 1983-10-25 06:42:51 |
| 2011-04-21 12:34:56 | 2011-05-01 12:34:56 |
| 2011-10-30 06:31:41 | 2011-11-09 06:31:41 |
| 2011-01-30 14:03:25 | 2011-02-09 14:03:25 |
| 2004-10-07 11:19:34 | 2004-10-17 11:19:34 |
+---------------------+---------------------+
SELECT d, ADDDATE(d, INTERVAL 10 HOUR) from t1;
+---------------------+------------------------------+
| d | ADDDATE(d, INTERVAL 10 HOUR) |
+---------------------+------------------------------+
| 2007-01-30 21:31:07 | 2007-01-31 07:31:07 |
| 1983-10-15 06:42:51 | 1983-10-15 16:42:51 |
| 2011-04-21 12:34:56 | 2011-04-21 22:34:56 |
| 2011-10-30 06:31:41 | 2011-10-30 16:31:41 |
| 2011-01-30 14:03:25 | 2011-01-31 00:03:25 |
| 2004-10-07 11:19:34 | 2004-10-07 21:19:34 |
+---------------------+------------------------------+
URL: https://mariadb.com/kb/en/adddate/https://mariadb.com/kb/en/adddate/ J� 3�{�� ��~� �M � n" ADDTIMESyntax
------
ADDTIME(expr1,expr2)
Description
-----------
ADDTIME() adds expr2 to expr1 and returns the result. expr1
is a time
or datetime expression, and expr2 is a time expression.
Examples
--------
SELECT ADDTIME('2007-12-31 23:59:59.999999', '1
1:1:1.000002');
+---------------------------------------------------------+
| ADDTIME('2007-12-31 23:59:59.999999', '1
1:1:1.000002') |
+---------------------------------------------------------+
| 2008-01-02 01:01:01.000001 |
+---------------------------------------------------------+
SELECT ADDTIME('01:00:00.999999', '02:00:00.999998');
+-----------------------------------------------+
| ADDTIME('01:00:00.999999', '02:00:00.999998') |
+-----------------------------------------------+
| 03:00:01.999997 |
+-----------------------------------------------+
URL: https://mariadb.com/kb/en/addtime/https://mariadb.com/kb/en/addtime/ �
M% CONVERT_TZSyntax
------
CONVERT_TZ(dt,from_tz,to_tz)
Description
-----------
CONVERT_TZ() converts a datetime value dt from the time zone
given by from_tz to the time zone given by to_tz and returns
the resulting value.
In order to use named time zones, such as GMT, MET or
Africa/Johannesburg, the time_zone tables must be loaded
(see mysql_tzinfo_to_sql).
No conversion will take place if the value falls outside of
the supported TIMESTAMP range ('1970-01-01 00:00:01' to
'2038-01-19 05:14:07' UTC) when converted from from_tz to
UTC.
This function returns NULL if the arguments are invalid (or
named time zones have not been loaded).
See time zones for more information.
Examples
--------
SELECT CONVERT_TZ('2016-01-01
12:00:00','+00:00','+10:00');
+-----------------------------------------------------+
| CONVERT_TZ('2016-01-01 12:00:00','+00:00','+10:00')
|
+-----------------------------------------------------+
| 2016-01-01 22:00:00 |
+-----------------------------------------------------+
Using named time zones (with the time zone tables loaded):
SELECT CONVERT_TZ('2016-01-01
12:00:00','GMT','Africa/Johannesburg');
+---------------------------------------------------------------+
| CONVERT_TZ('2016-01-01
12:00:00','GMT','Africa/Johannesburg') |
+---------------------------------------------------------------+
| 2016-01-01 14:00:00 |
+---------------------------------------------------------------+
The value is out of the TIMESTAMP range, so no conversion
takes place:
SELECT CONVERT_TZ('1969-12-31
22:00:00','+00:00','+10:00');
+-----------------------------------------------------+
| CONVERT_TZ('1969-12-31 22:00:00','+00:00','+10:00')
|
+-----------------------------------------------------+
| 1969-12-31 22:00:00 |
+-----------------------------------------------------+
URL: https://mariadb.com/kb/en/convert_tz/https://mariadb.com/kb/en/convert_tz/ � 0# DATEDIFFSyntax
------
DATEDIFF(expr1,expr2)
Description
-----------
DATEDIFF() returns (expr1 – expr2) expressed
as a value in days from one date to the other. expr1 and
expr2 are date
or date-and-time expressions. Only the date parts of the
values are used in the
calculation.
Examples
--------
SELECT DATEDIFF('2007-12-31 23:59:59','2007-12-30');
+----------------------------------------------+
| DATEDIFF('2007-12-31 23:59:59','2007-12-30') |
+----------------------------------------------+
| 1 |
+----------------------------------------------+
SELECT DATEDIFF('2010-11-30 23:59:59','2010-12-31');
+----------------------------------------------+
| DATEDIFF('2010-11-30 23:59:59','2010-12-31') |
+----------------------------------------------+
| -31 |
+----------------------------------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
("2007-01-30 21:31:07"),
("1983-10-15 06:42:51"),
("2011-04-21 12:34:56"),
("2011-10-30 06:31:41"),
("2011-01-30 14:03:25"),
("2004-10-07 11:19:34");
SELECT NOW();
+---------------------+
| NOW() |
+---------------------+
| 2011-05-23 10:56:05 |
+---------------------+
SELECT d, DATEDIFF(NOW(),d) FROM t1;
+---------------------+-------------------+
| d | DATEDIFF(NOW(),d) |
+---------------------+-------------------+
| 2007-01-30 21:31:07 | 1574 |
| 1983-10-15 06:42:51 | 10082 |
| 2011-04-21 12:34:56 | 32 |
| 2011-10-30 06:31:41 | -160 |
| 2011-01-30 14:03:25 | 113 |
| 2004-10-07 11:19:34 | 2419 |
+---------------------+-------------------+
URL: https://mariadb.com/kb/en/datediff/https://mariadb.com/kb/en/datediff/ � � # DATE_ADDSyntax
------
DATE_ADD(date,INTERVAL expr unit)
Description
-----------
Performs date arithmetic. The date argument specifies the
starting date or datetime value. expr is an expression
specifying the
interval value to be added or subtracted from the starting
date. expr is a
string; it may start with a "-" for negative intervals.
unit is a
keyword indicating the units in which the expression should
be interpreted. See Date and Time Units for a complete list
of permitted units.
See also DATE_SUB().
Examples
--------
SELECT '2008-12-31 23:59:59' + INTERVAL 1 SECOND;
+-------------------------------------------+
| '2008-12-31 23:59:59' + INTERVAL 1 SECOND |
+-------------------------------------------+
| 2009-01-01 00:00:00 |
+-------------------------------------------+
SELECT INTERVAL 1 DAY + '2008-12-31';
+-------------------------------+
| INTERVAL 1 DAY + '2008-12-31' |
+-------------------------------+
| 2009-01-01 |
+-------------------------------+
SELECT '2005-01-01' - INTERVAL 1 SECOND;
+----------------------------------+
| '2005-01-01' - INTERVAL 1 SECOND |
+----------------------------------+
| 2004-12-31 23:59:59 |
+----------------------------------+
SELECT DATE_ADD('2000-12-31 23:59:59', INTERVAL 1 SECOND);
+----------------------------------------------------+
| DATE_ADD('2000-12-31 23:59:59', INTERVAL 1 SECOND) |
+----------------------------------------------------+
| 2001-01-01 00:00:00 |
+----------------------------------------------------+
SELECT DATE_ADD('2010-12-31 23:59:59', INTERVAL 1 DAY);
+-------------------------------------------------+
| DATE_ADD('2010-12-31 23:59:59', INTERVAL 1 DAY) |
+-------------------------------------------------+
| 2011-01-01 23:59:59 |
+-------------------------------------------------+
SELECT DATE_ADD('2100-12-31 23:59:59', INTERVAL '1:1'
MINUTE_SECOND);
+---------------------------------------------------------------+
| DATE_ADD('2100-12-31 23:59:59', INTERVAL '1:1'
MINUTE_SECOND) |
+---------------------------------------------------------------+
| 2101-01-01 00:01:00 |
+---------------------------------------------------------------+
SELECT DATE_ADD('1900-01-01 00:00:00', INTERVAL '-1 10'
DAY_HOUR);
+------------------------------------------------------------+
| DATE_ADD('1900-01-01 00:00:00', INTERVAL '-1 10'
DAY_HOUR) |
+------------------------------------------------------------+
| 1899-12-30 14:00:00 |
+------------------------------------------------------------+
SELECT DATE_ADD('1992-12-31 23:59:59.000002', INTERVAL
'1.999999' SECOND_MICROSECOND);
+--------------------------------------------------------------------------------+
| DATE_ADD('1992-12-31 23:59:59.000002', INTERVAL
'1.999999' SECOND_MICROSECOND) |
+--------------------------------------------------------------------------------+
| 1993-01-01 00:00:01.000001 |
+--------------------------------------------------------------------------------+
URL: https://mariadb.com/kb/en/date_add/https://mariadb.com/kb/en/date_add/ �� ; i�� ���k �n � Z& DATE_FORMATSyntax
------
DATE_FORMAT(date, format[, locale])
Description
-----------
Formats the date value according to the format string.
The language used for the names is controlled by the value
of the lc_time_names system variable. See server locale for
more on the supported locales.
The options that can be used by DATE_FORMAT(), as well as
its inverse STR_TO_DATE() and the FROM_UNIXTIME() function,
are:
Option | Description |
%a | Short weekday name in current locale (Variable
lc_time_names). |
%b | Short form month name in current locale. For locale
en_US this is one of:
Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov or Dec. |
%c | Month with 1 or 2 digits. |
%D | Day with English suffix 'th', 'nd', 'st' or
'rd''. (1st, 2nd, 3rd...). |
%d | Day with 2 digits. |
%e | Day with 1 or 2 digits. |
%f | Sub seconds 6 digits. |
%H | Hour with 2 digits between 00-23. |
%h | Hour with 2 digits between 01-12. |
%I | Hour with 2 digits between 01-12. |
%i | Minute with 2 digits. |
%j | Day of the year (001-366) |
%k | Hour with 1 digits between 0-23. |
%l | Hour with 1 digits between 1-12. |
%M | Full month name in current locale (Variable
lc_time_names). |
%m | Month with 2 digits. |
%p | AM/PM according to current locale (Variable
lc_time_names). |
%r | Time in 12 hour format, followed by AM/PM. Short for
'%I:%i:%S %p'. |
%S | Seconds with 2 digits. |
%s | Seconds with 2 digits. |
%T | Time in 24 hour format. Short for '%H:%i:%S'. |
%U | Week number (00-53), when first day of the week is
Sunday. |
%u | Week number (00-53), when first day of the week is
Monday. |
%V | Week number (01-53), when first day of the week is
Sunday. Used with %X. |
%v | Week number (01-53), when first day of the week is
Monday. Used with %x. |
%W | Full weekday name in current locale (Variable
lc_time_names). |
%w | Day of the week. 0 = Sunday, 6 = Saturday. |
%X | Year with 4 digits when first day of the week is
Sunday. Used with %V. |
%x | Year with 4 digits when first day of the week is
Monday. Used with %v. |
%Y | Year with 4 digits. |
%y | Year with 2 digits. |
%# | For str_to_date(), skip all numbers. |
%. | For str_to_date(), skip all punctation characters. |
%@ | For str_to_date(), skip all alpha characters. |
%% | A literal % character. |
To get a date in one of the standard formats, GET_FORMAT()
can be used.
Examples
--------
SELECT DATE_FORMAT('2009-10-04 22:23:00', '%W %M %Y');
+------------------------------------------------+
| DATE_FORMAT('2009-10-04 22:23:00', '%W %M %Y') |
+------------------------------------------------+
| Sunday October 2009 |
+------------------------------------------------+
SELECT DATE_FORMAT('2007-10-04 22:23:00', '%H:%i:%s');
+------------------------------------------------+
| DATE_FORMAT('2007-10-04 22:23:00', '%H:%i:%s') |
+------------------------------------------------+
| 22:23:00 |
+------------------------------------------------+
SELECT DATE_FORMAT('1900-10-04 22:23:00', '%D %y %a %d %m
%b %j');
+------------------------------------------------------------+
| DATE_FORMAT('1900-10-04 22:23:00', '%D %y %a %d %m %b
%j') |
+------------------------------------------------------------+
| 4th 00 Thu 04 10 Oct 277 |
+------------------------------------------------------------+
SELECT DATE_FORMAT('1997-10-04 22:23:00', '%H %k %I %r %T
%S %w');
+------------------------------------------------------------+
| DATE_FORMAT('1997-10-04 22:23:00', '%H %k %I %r %T %S
%w') |
+------------------------------------------------------------+
| 22 22 10 10:23:00 PM 22:23:00 00 6 |
+------------------------------------------------------------+
SELECT DATE_FORMAT('1999-01-01', '%X %V');
+------------------------------------+
| DATE_FORMAT('1999-01-01', '%X %V') |
+------------------------------------+
| 1998 52 |
+------------------------------------+
SELECT DATE_FORMAT('2006-06-00', '%d');
+---------------------------------+
| DATE_FORMAT('2006-06-00', '%d') |
+---------------------------------+
| 00 |
+---------------------------------+
Optionally, the locale can be explicitly specified as the
third DATE_FORMAT() argument. Doing so makes the function
independent from the session settings, and the three
argument version of DATE_FORMAT() can be used in virtual
indexed and persistent generated-columns:
SELECT DATE_FORMAT('2006-01-01', '%W', 'el_GR');
+------------------------------------------+
| DATE_FORMAT('2006-01-01', '%W', 'el_GR') |
+------------------------------------------+
| Κυριακή |
+------------------------------------------+
URL: https://mariadb.com/kb/en/date_format/https://mariadb.com/kb/en/date_format/ � �# DATE_SUBSyntax
------
DATE_SUB(date,INTERVAL expr unit)
Description
-----------
Performs date arithmetic. The date argument specifies the
starting date or datetime value. expr is an expression
specifying the
interval value to be added or subtracted from the starting
date. expr is a
string; it may start with a "-" for negative intervals.
unit is a
keyword indicating the units in which the expression should
be interpreted. See Date and Time Units for a complete list
of permitted units.
See also DATE_ADD().
Examples
--------
SELECT DATE_SUB('1998-01-02', INTERVAL 31 DAY);
+-----------------------------------------+
| DATE_SUB('1998-01-02', INTERVAL 31 DAY) |
+-----------------------------------------+
| 1997-12-02 |
+-----------------------------------------+
SELECT DATE_SUB('2005-01-01 00:00:00', INTERVAL '1
1:1:1' DAY_SECOND);
+----------------------------------------------------------------+
| DATE_SUB('2005-01-01 00:00:00', INTERVAL '1 1:1:1'
DAY_SECOND) |
+----------------------------------------------------------------+
| 2004-12-30 22:58:59 |
+----------------------------------------------------------------+
URL: https://mariadb.com/kb/en/date_sub/https://mariadb.com/kb/en/date_sub/ �� �x�E� � � �" DAYNAMESyntax
------
DAYNAME(date)
Description
-----------
Returns the name of the weekday for date. The language used
for the name is controlled by the value
of the lc_time_names system variable. See server locale for
more on the supported locales.
Examples
--------
SELECT DAYNAME('2007-02-03');
+-----------------------+
| DAYNAME('2007-02-03') |
+-----------------------+
| Saturday |
+-----------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
("2007-01-30 21:31:07"),
("1983-10-15 06:42:51"),
("2011-04-21 12:34:56"),
("2011-10-30 06:31:41"),
("2011-01-30 14:03:25"),
("2004-10-07 11:19:34");
SELECT d, DAYNAME(d) FROM t1;
+---------------------+------------+
| d | DAYNAME(d) |
+---------------------+------------+
| 2007-01-30 21:31:07 | Tuesday |
| 1983-10-15 06:42:51 | Saturday |
| 2011-04-21 12:34:56 | Thursday |
| 2011-10-30 06:31:41 | Sunday |
| 2011-01-30 14:03:25 | Sunday |
| 2004-10-07 11:19:34 | Thursday |
+---------------------+------------+
Changing the locale:
SET lc_time_names = 'fr_CA';
SELECT DAYNAME('2013-04-01');
+-----------------------+
| DAYNAME('2013-04-01') |
+-----------------------+
| lundi |
+-----------------------+
URL: https://mariadb.com/kb/en/dayname/https://mariadb.com/kb/en/dayname/ �
a% DAYOFMONTHSyntax
------
DAYOFMONTH(date)
Description
-----------
Returns the day of the month for date, in the range 1 to 31,
or 0
for dates such as '0000-00-00' or '2008-00-00' which
have a zero day
part.
DAY() is a synonym.
Examples
--------
SELECT DAYOFMONTH('2007-02-03');
+--------------------------+
| DAYOFMONTH('2007-02-03') |
+--------------------------+
| 3 |
+--------------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
("2007-01-30 21:31:07"),
("1983-10-15 06:42:51"),
("2011-04-21 12:34:56"),
("2011-10-30 06:31:41"),
("2011-01-30 14:03:25"),
("2004-10-07 11:19:34");
SELECT d FROM t1 where DAYOFMONTH(d) = 30;
+---------------------+
| d |
+---------------------+
| 2007-01-30 21:31:07 |
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
+---------------------+
URL: https://mariadb.com/kb/en/dayofmonth/https://mariadb.com/kb/en/dayofmonth/ � "$ DAYOFWEEKSyntax
------
DAYOFWEEK(date)
Description
-----------
Returns the day of the week index for the date (1 = Sunday,
2 = Monday, ..., 7 =
Saturday). These index values correspond to the ODBC
standard.
This contrasts with WEEKDAY() which follows a different
index numbering
(0 = Monday, 1 = Tuesday, ... 6 = Sunday).
Examples
--------
SELECT DAYOFWEEK('2007-02-03');
+-------------------------+
| DAYOFWEEK('2007-02-03') |
+-------------------------+
| 7 |
+-------------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
("2007-01-30 21:31:07"),
("1983-10-15 06:42:51"),
("2011-04-21 12:34:56"),
("2011-10-30 06:31:41"),
("2011-01-30 14:03:25"),
("2004-10-07 11:19:34");
SELECT d, DAYNAME(d), DAYOFWEEK(d), WEEKDAY(d) from t1;
+---------------------+------------+--------------+------------+
| d | DAYNAME(d) | DAYOFWEEK(d) | WEEKDAY(d) |
+---------------------+------------+--------------+------------+
| 2007-01-30 21:31:07 | Tuesday | 3 | 1 |
| 1983-10-15 06:42:51 | Saturday | 7 | 5 |
| 2011-04-21 12:34:56 | Thursday | 5 | 3 |
| 2011-10-30 06:31:41 | Sunday | 1 | 6 |
| 2011-01-30 14:03:25 | Sunday | 1 | 6 |
| 2004-10-07 11:19:34 | Thursday | 5 | 3 |
+---------------------+------------+--------------+------------+
URL: https://mariadb.com/kb/en/dayofweek/https://mariadb.com/kb/en/dayofweek/ � y" EXTRACTSyntax
------
EXTRACT(unit FROM date)
Description
-----------
The EXTRACT() function extracts the required unit from the
date. See Date and Time Units for a complete list of
permitted units.
In MariaDB 10.0.7 and MariaDB 5.5.35, EXTRACT (HOUR FROM
...) was changed to return a value from 0 to 23, adhering to
the SQL standard. Until MariaDB 10.0.6 and MariaDB 5.5.34,
and in all versions of MySQL at least as of MySQL 5.7, it
could return a value > 23. HOUR() is not a standard
function, so continues to adhere to the old behaviour
inherited from MySQL.
Examples
--------
SELECT EXTRACT(YEAR FROM '2009-07-02');
+---------------------------------+
| EXTRACT(YEAR FROM '2009-07-02') |
+---------------------------------+
| 2009 |
+---------------------------------+
SELECT EXTRACT(YEAR_MONTH FROM '2009-07-02 01:02:03');
+------------------------------------------------+
| EXTRACT(YEAR_MONTH FROM '2009-07-02 01:02:03') |
+------------------------------------------------+
| 200907 |
+------------------------------------------------+
SELECT EXTRACT(DAY_MINUTE FROM '2009-07-02 01:02:03');
+------------------------------------------------+
| EXTRACT(DAY_MINUTE FROM '2009-07-02 01:02:03') |
+------------------------------------------------+
| 20102 |
+------------------------------------------------+
SELECT EXTRACT(MICROSECOND FROM '2003-01-02
10:30:00.000123');
+--------------------------------------------------------+
| EXTRACT(MICROSECOND FROM '2003-01-02 10:30:00.000123') |
+--------------------------------------------------------+
| 123 |
+--------------------------------------------------------+
From MariaDB 10.0.7 and MariaDB 5.5.35, EXTRACT (HOUR
FROM...) returns a value from 0 to 23, as per the SQL
standard. HOUR is not a standard function, so continues to
adhere to the old behaviour inherited from MySQL.
SELECT EXTRACT(HOUR FROM '26:30:00'), HOUR('26:30:00');
+-------------------------------+------------------+
| EXTRACT(HOUR FROM '26:30:00') | HOUR('26:30:00') |
+-------------------------------+------------------+
| 2 | 26 |
+-------------------------------+------------------+
URL: https://mariadb.com/kb/en/extract/https://mariadb.com/kb/en/extract/ !��]&�
��J �� �
h( FROM_UNIXTIMESyntax
------
FROM_UNIXTIME(unix_timestamp),
FROM_UNIXTIME(unix_timestamp,format)
Description
-----------
Returns a representation of the unix_timestamp argument as a
value in
'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format,
depending on
whether the function is used in a string or numeric context.
The value
is expressed in the current time zone. unix_timestamp is an
internal
timestamp value such as is produced by the UNIX_TIMESTAMP()
function.
If format is given, the result is formatted according to the
format
string, which is used the same way as listed in the entry
for the
DATE_FORMAT() function.
Timestamps in MariaDB have a maximum value of 2147483647,
equivalent to 2038-01-19 05:14:07. This is due to the
underlying 32-bit limitation. Using the function on a
timestamp beyond this will result in NULL being returned.
Use DATETIME as a storage type if you require dates beyond
this.
The options that can be used by FROM_UNIXTIME(), as well as
DATE_FORMAT() and STR_TO_DATE(), are:
Option | Description |
%a | Short weekday name in current locale (Variable
lc_time_names). |
%b | Short form month name in current locale. For locale
en_US this is one of:
Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov or Dec. |
%c | Month with 1 or 2 digits. |
%D | Day with English suffix 'th', 'nd', 'st' or
'rd''. (1st, 2nd, 3rd...). |
%d | Day with 2 digits. |
%e | Day with 1 or 2 digits. |
%f | Sub seconds 6 digits. |
%H | Hour with 2 digits between 00-23. |
%h | Hour with 2 digits between 01-12. |
%I | Hour with 2 digits between 01-12. |
%i | Minute with 2 digits. |
%j | Day of the year (001-366) |
%k | Hour with 1 digits between 0-23. |
%l | Hour with 1 digits between 1-12. |
%M | Full month name in current locale (Variable
lc_time_names). |
%m | Month with 2 digits. |
%p | AM/PM according to current locale (Variable
lc_time_names). |
%r | Time in 12 hour format, followed by AM/PM. Short for
'%I:%i:%S %p'. |
%S | Seconds with 2 digits. |
%s | Seconds with 2 digits. |
%T | Time in 24 hour format. Short for '%H:%i:%S'. |
%U | Week number (00-53), when first day of the week is
Sunday. |
%u | Week number (00-53), when first day of the week is
Monday. |
%V | Week number (01-53), when first day of the week is
Sunday. Used with %X. |
%v | Week number (01-53), when first day of the week is
Monday. Used with %x. |
%W | Full weekday name in current locale (Variable
lc_time_names). |
%w | Day of the week. 0 = Sunday, 1 = Saturday. |
%X | Year with 4 digits when first day of the week is
Sunday. Used with %V. |
%x | Year with 4 digits when first day of the week is
Sunday. Used with %v. |
%Y | Year with 4 digits. |
%y | Year with 2 digits. |
%# | For str_to_date(), skip all numbers. |
%. | For str_to_date(), skip all punctation characters. |
%@ | For str_to_date(), skip all alpha characters. |
%% | A literal % character. |
Performance Considerations
If your session time zone is set to SYSTEM (the default),
FROM_UNIXTIME() will call the OS function to convert the
data using the system time zone. At least on Linux, the
corresponding function (localtime_r) uses a global mutex
inside glibc that can cause contention under high concurrent
load.
Set your time zone to a named time zone to avoid this issue.
See mysql time zone tables for details on how to do this.
Examples
--------
SELECT FROM_UNIXTIME(1196440219);
+---------------------------+
| FROM_UNIXTIME(1196440219) |
+---------------------------+
| 2007-11-30 11:30:19 |
+---------------------------+
SELECT FROM_UNIXTIME(1196440219) + 0;
+-------------------------------+
| FROM_UNIXTIME(1196440219) + 0 |
+-------------------------------+
| 20071130113019.000000 |
+-------------------------------+
SELECT FROM_UNIXTIME(UNIX_TIMESTAMP(), '%Y %D %M %h:%i:%s
%x');
+---------------------------------------------------------+
| FROM_UNIXTIME(UNIX_TIMESTAMP(), '%Y %D %M %h:%i:%s %x')
|
+---------------------------------------------------------+
| 2010 27th March 01:03:47 2010 |
+---------------------------------------------------------+
URL: https://mariadb.com/kb/en/from_unixtime/https://mariadb.com/kb/en/from_unixtime/ �
v% GET_FORMATSyntax
------
GET_FORMAT({DATE|DATETIME|TIME},
{'EUR'|'USA'|'JIS'|'ISO'|'INTERNAL'})
Description
-----------
Returns a format string. This function is useful in
combination with
the DATE_FORMAT() and the STR_TO_DATE() functions.
Possible result formats are:
Function Call | Result Format |
GET_FORMAT(DATE,'EUR') | '%d.%m.%Y' |
GET_FORMAT(DATE,'USA') | '%m.%d.%Y' |
GET_FORMAT(DATE,'JIS') | '%Y-%m-%d' |
GET_FORMAT(DATE,'ISO') | '%Y-%m-%d' |
GET_FORMAT(DATE,'INTERNAL') | '%Y%m%d' |
GET_FORMAT(DATETIME,'EUR') | '%Y-%m-%d %H.%i.%s' |
GET_FORMAT(DATETIME,'USA') | '%Y-%m-%d %H.%i.%s' |
GET_FORMAT(DATETIME,'JIS') | '%Y-%m-%d %H:%i:%s' |
GET_FORMAT(DATETIME,'ISO') | '%Y-%m-%d %H:%i:%s' |
GET_FORMAT(DATETIME,'INTERNAL') | '%Y%m%d%H%i%s' |
GET_FORMAT(TIME,'EUR') | '%H.%i.%s' |
GET_FORMAT(TIME,'USA') | '%h:%i:%s %p' |
GET_FORMAT(TIME,'JIS') | '%H:%i:%s' |
GET_FORMAT(TIME,'ISO') | '%H:%i:%s' |
GET_FORMAT(TIME,'INTERNAL') | '%H%i%s' |
Examples
--------
Obtaining the string matching to the standard European date
format:
SELECT GET_FORMAT(DATE, 'EUR');
+-------------------------+
| GET_FORMAT(DATE, 'EUR') |
+-------------------------+
| %d.%m.%Y |
+-------------------------+
Using the same string to format a date:
SELECT DATE_FORMAT('2003-10-03',GET_FORMAT(DATE,'EUR'));
+--------------------------------------------------+
| DATE_FORMAT('2003-10-03',GET_FORMAT(DATE,'EUR')) |
+--------------------------------------------------+
| 03.10.2003 |
+--------------------------------------------------+
SELECT STR_TO_DATE('10.31.2003',GET_FORMAT(DATE,'USA'));
+--------------------------------------------------+
| STR_TO_DATE('10.31.2003',GET_FORMAT(DATE,'USA')) |
+--------------------------------------------------+
| 2003-10-31 |
+--------------------------------------------------+
URL: https://mariadb.com/kb/en/get_format/https://mariadb.com/kb/en/get_format/ �� �-� �k � � HOURSyntax
------
HOUR(time)
Description
-----------
Returns the hour for time. The range of the return value is
0 to 23
for time-of-day values. However, the range of TIME values
actually is
much larger, so HOUR can return values greater than 23.
The return value is always positive, even if a negative TIME
value is provided.
Examples
--------
SELECT HOUR('10:05:03');
+------------------+
| HOUR('10:05:03') |
+------------------+
| 10 |
+------------------+
SELECT HOUR('272:59:59');
+-------------------+
| HOUR('272:59:59') |
+-------------------+
| 272 |
+-------------------+
Difference between EXTRACT (HOUR FROM ...) (>= MariaDB
10.0.7 and MariaDB 5.5.35) and HOUR:
SELECT EXTRACT(HOUR FROM '26:30:00'), HOUR('26:30:00');
+-------------------------------+------------------+
| EXTRACT(HOUR FROM '26:30:00') | HOUR('26:30:00') |
+-------------------------------+------------------+
| 2 | 26 |
+-------------------------------+------------------+
URL: https://mariadb.com/kb/en/hour/https://mariadb.com/kb/en/hour/ � # LAST_DAYSyntax
------
LAST_DAY(date)
Description
-----------
Takes a date or datetime value and returns the corresponding
value for
the last day of the month. Returns NULL if the argument is
invalid.
Examples
--------
SELECT LAST_DAY('2003-02-05');
+------------------------+
| LAST_DAY('2003-02-05') |
+------------------------+
| 2003-02-28 |
+------------------------+
SELECT LAST_DAY('2004-02-05');
+------------------------+
| LAST_DAY('2004-02-05') |
+------------------------+
| 2004-02-29 |
+------------------------+
SELECT LAST_DAY('2004-01-01 01:01:01');
+---------------------------------+
| LAST_DAY('2004-01-01 01:01:01') |
+---------------------------------+
| 2004-01-31 |
+---------------------------------+
SELECT LAST_DAY('2003-03-32');
+------------------------+
| LAST_DAY('2003-03-32') |
+------------------------+
| NULL |
+------------------------+
1 row in set, 1 warning (0.00 sec)
Warning (Code 1292): Incorrect datetime value:
'2003-03-32'
URL: https://mariadb.com/kb/en/last_day/https://mariadb.com/kb/en/last_day/ � c# MAKEDATESyntax
------
MAKEDATE(year,dayofyear)
Description
-----------
Returns a date, given year and day-of-year values. dayofyear
must be
greater than 0 or the result is NULL.
Examples
--------
SELECT MAKEDATE(2011,31), MAKEDATE(2011,32);
+-------------------+-------------------+
| MAKEDATE(2011,31) | MAKEDATE(2011,32) |
+-------------------+-------------------+
| 2011-01-31 | 2011-02-01 |
+-------------------+-------------------+
SELECT MAKEDATE(2011,365), MAKEDATE(2014,365);
+--------------------+--------------------+
| MAKEDATE(2011,365) | MAKEDATE(2014,365) |
+--------------------+--------------------+
| 2011-12-31 | 2014-12-31 |
+--------------------+--------------------+
SELECT MAKEDATE(2011,0);
+------------------+
| MAKEDATE(2011,0) |
+------------------+
| NULL |
+------------------+
URL: https://mariadb.com/kb/en/makedate/https://mariadb.com/kb/en/makedate/ � # MAKETIMESyntax
------
MAKETIME(hour,minute,second)
Description
-----------
Returns a time value calculated from the hour, minute, and
second arguments.
If minute or second are out of the range 0 to 60, NULL is
returned. The hour can be in the range -838 to 838, outside
of which the value is truncated with a warning.
Examples
--------
SELECT MAKETIME(13,57,33);
+--------------------+
| MAKETIME(13,57,33) |
+--------------------+
| 13:57:33 |
+--------------------+
SELECT MAKETIME(-13,57,33);
+---------------------+
| MAKETIME(-13,57,33) |
+---------------------+
| -13:57:33 |
+---------------------+
SELECT MAKETIME(13,67,33);
+--------------------+
| MAKETIME(13,67,33) |
+--------------------+
| NULL |
+--------------------+
SELECT MAKETIME(-1000,57,33);
+-----------------------+
| MAKETIME(-1000,57,33) |
+-----------------------+
| -838:59:59 |
+-----------------------+
1 row in set, 1 warning (0.00 sec)
SHOW WARNINGS;
+---------+------+-----------------------------------------------+
| Level | Code | Message |
+---------+------+-----------------------------------------------+
| Warning | 1292 | Truncated incorrect time value:
'-1000:57:33' |
+---------+------+-----------------------------------------------+
URL: https://mariadb.com/kb/en/maketime/https://mariadb.com/kb/en/maketime/ � �& MICROSECONDSyntax
------
MICROSECOND(expr)
Description
-----------
Returns the microseconds from the time or datetime
expression expr as a number in the range from 0 to 999999.
If expr is a time with no microseconds, zero is returned,
while if expr is a date with no time, zero with a warning is
returned.
Examples
--------
SELECT MICROSECOND('12:00:00.123456');
+--------------------------------+
| MICROSECOND('12:00:00.123456') |
+--------------------------------+
| 123456 |
+--------------------------------+
SELECT MICROSECOND('2009-12-31 23:59:59.000010');
+-------------------------------------------+
| MICROSECOND('2009-12-31 23:59:59.000010') |
+-------------------------------------------+
| 10 |
+-------------------------------------------+
SELECT MICROSECOND('2013-08-07 12:13:14');
+------------------------------------+
| MICROSECOND('2013-08-07 12:13:14') |
+------------------------------------+
| 0 |
+------------------------------------+
SELECT MICROSECOND('2013-08-07');
+---------------------------+
| MICROSECOND('2013-08-07') |
+---------------------------+
| 0 |
+---------------------------+
1 row in set, 1 warning (0.00 sec)
SHOW WARNINGS;
+---------+------+----------------------------------------------+
| Level | Code | Message |
+---------+------+----------------------------------------------+
| Warning | 1292 | Truncated incorrect time value:
'2013-08-07' |
+---------+------+----------------------------------------------+
URL: https://mariadb.com/kb/en/microsecond/https://mariadb.com/kb/en/microsecond/ R+ Jl�*B �h� �� � � NOWSyntax
------
NOW([precision])
CURRENT_TIMESTAMP
CURRENT_TIMESTAMP([precision])
LOCALTIME, LOCALTIME([precision])
LOCALTIMESTAMP
LOCALTIMESTAMP([precision])
Description
-----------
Returns the current date and time as a value in 'YYYY-MM-DD
HH:MM:SS'
or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the
function is
used in a string or numeric context. The value is expressed
in the
current time zone.
The optional precision determines the microsecond precision.
See Microseconds in MariaDB.
NOW() (or its synonyms) can be used as the default value for
TIMESTAMP columns as well as, since MariaDB 10.0.1, DATETIME
columns. Before MariaDB 10.0.1, it was only possible for a
single TIMESTAMP column per table to contain the
CURRENT_TIMESTAMP as its default.
When displayed in the INFORMATION_SCHEMA.COLUMNS table, a
default CURRENT TIMESTAMP is displayed as CURRENT_TIMESTAMP
up until MariaDB 10.2.2, and as current_timestamp() from
MariaDB 10.2.3, due to to MariaDB 10.2 accepting expressions
in the DEFAULT clause.
Examples
--------
SELECT NOW();
+---------------------+
| NOW() |
+---------------------+
| 2010-03-27 13:13:25 |
+---------------------+
SELECT NOW() + 0;
+-----------------------+
| NOW() + 0 |
+-----------------------+
| 20100327131329.000000 |
+-----------------------+
With precision:
SELECT CURRENT_TIMESTAMP(2);
+------------------------+
| CURRENT_TIMESTAMP(2) |
+------------------------+
| 2018-07-10 09:47:26.24 |
+------------------------+
Used as a default TIMESTAMP:
CREATE TABLE t (createdTS TIMESTAMP NOT NULL DEFAULT
CURRENT_TIMESTAMP);
From MariaDB 10.2.2:
SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE
TABLE_SCHEMA='test'
AND COLUMN_NAME LIKE '%ts%'\G
*************************** 1. row
***************************
TABLE_CATALOG: def
TABLE_SCHEMA: test
TABLE_NAME: t
COLUMN_NAME: ts
ORDINAL_POSITION: 1
COLUMN_DEFAULT: current_timestamp()
...
URL: https://mariadb.com/kb/en/now/https://mariadb.com/kb/en/now/ �
+% PERIOD_ADDSyntax
------
PERIOD_ADD(P,N)
Description
-----------
Adds N months to period P. P is in the format YYMM or
YYYYMM, and is not a date value. If P contains a two-digit
year, values from 00 to 69 are converted to from 2000 to
2069, while values from 70 are converted to 1970 upwards.
Returns a value in the format YYYYMM.
Examples
--------
SELECT PERIOD_ADD(200801,2);
+----------------------+
| PERIOD_ADD(200801,2) |
+----------------------+
| 200803 |
+----------------------+
SELECT PERIOD_ADD(6910,2);
+--------------------+
| PERIOD_ADD(6910,2) |
+--------------------+
| 206912 |
+--------------------+
SELECT PERIOD_ADD(7010,2);
+--------------------+
| PERIOD_ADD(7010,2) |
+--------------------+
| 197012 |
+--------------------+
URL: https://mariadb.com/kb/en/period_add/https://mariadb.com/kb/en/period_add/ � w& PERIOD_DIFFSyntax
------
PERIOD_DIFF(P1,P2)
Description
-----------
Returns the number of months between periods P1 and P2. P1
and P2
can be in the format YYMM or YYYYMM, and are not date
values.
If P1 or P2 contains a two-digit year, values from 00 to 69
are converted to from 2000 to 2069, while values from 70 are
converted to 1970 upwards.
Examples
--------
SELECT PERIOD_DIFF(200802,200703);
+----------------------------+
| PERIOD_DIFF(200802,200703) |
+----------------------------+
| 11 |
+----------------------------+
SELECT PERIOD_DIFF(6902,6803);
+------------------------+
| PERIOD_DIFF(6902,6803) |
+------------------------+
| 11 |
+------------------------+
SELECT PERIOD_DIFF(7002,6803);
+------------------------+
| PERIOD_DIFF(7002,6803) |
+------------------------+
| -1177 |
+------------------------+
URL: https://mariadb.com/kb/en/period_diff/https://mariadb.com/kb/en/period_diff/ � �& SEC_TO_TIMESyntax
------
SEC_TO_TIME(seconds)
Description
-----------
Returns the seconds argument, converted to hours, minutes,
and
seconds, as a TIME value. The range of the result is
constrained to
that of the TIME data type. A warning occurs if the argument
corresponds to a value outside that range.
The time will be returned in the format hh:mm:ss, or hhmmss
if used in a numeric calculation.
Examples
--------
SELECT SEC_TO_TIME(12414);
+--------------------+
| SEC_TO_TIME(12414) |
+--------------------+
| 03:26:54 |
+--------------------+
SELECT SEC_TO_TIME(12414)+0;
+----------------------+
| SEC_TO_TIME(12414)+0 |
+----------------------+
| 32654 |
+----------------------+
SELECT SEC_TO_TIME(9999999);
+----------------------+
| SEC_TO_TIME(9999999) |
+----------------------+
| 838:59:59 |
+----------------------+
1 row in set, 1 warning (0.00 sec)
SHOW WARNINGS;
+---------+------+-------------------------------------------+
| Level | Code | Message |
+---------+------+-------------------------------------------+
| Warning | 1292 | Truncated incorrect time value:
'9999999' |
+---------+------+-------------------------------------------+
URL: https://mariadb.com/kb/en/sec_to_time/https://mariadb.com/kb/en/sec_to_time/ � I ��h � �Ns �n � |& STR_TO_DATESyntax
------
STR_TO_DATE(str,format)
Description
-----------
This is the inverse of the DATE_FORMAT() function. It takes
a string str and a format string format. STR_TO_DATE()
returns a
DATETIME value if the format string contains both date and
time parts, or a
DATE or TIME value if the string contains only date or time
parts.
The date, time, or datetime values contained in str should
be given in the format indicated by format. If str contains
an illegal date, time, or datetime value, STR_TO_DATE()
returns NULL. An illegal value also produces a warning.
The options that can be used by STR_TO_DATE(), as well as
its inverse DATE_FORMAT() and the FROM_UNIXTIME() function,
are:
Option | Description |
%a | Short weekday name in current locale (Variable
lc_time_names). |
%b | Short form month name in current locale. For locale
en_US this is one of:
Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov or Dec. |
%c | Month with 1 or 2 digits. |
%D | Day with English suffix 'th', 'nd', 'st' or
'rd''. (1st, 2nd, 3rd...). |
%d | Day with 2 digits. |
%e | Day with 1 or 2 digits. |
%f | Sub seconds 6 digits. |
%H | Hour with 2 digits between 00-23. |
%h | Hour with 2 digits between 01-12. |
%I | Hour with 2 digits between 01-12. |
%i | Minute with 2 digits. |
%j | Day of the year (001-366) |
%k | Hour with 1 digits between 0-23. |
%l | Hour with 1 digits between 1-12. |
%M | Full month name in current locale (Variable
lc_time_names). |
%m | Month with 2 digits. |
%p | AM/PM according to current locale (Variable
lc_time_names). |
%r | Time in 12 hour format, followed by AM/PM. Short for
'%I:%i:%S %p'. |
%S | Seconds with 2 digits. |
%s | Seconds with 2 digits. |
%T | Time in 24 hour format. Short for '%H:%i:%S'. |
%U | Week number (00-53), when first day of the week is
Sunday. |
%u | Week number (00-53), when first day of the week is
Monday. |
%V | Week number (01-53), when first day of the week is
Sunday. Used with %X. |
%v | Week number (01-53), when first day of the week is
Monday. Used with %x. |
%W | Full weekday name in current locale (Variable
lc_time_names). |
%w | Day of the week. 0 = Sunday, 6 = Saturday. |
%X | Year with 4 digits when first day of the week is
Sunday. Used with %V. |
%x | Year with 4 digits when first day of the week is
Monday. Used with %v. |
%Y | Year with 4 digits. |
%y | Year with 2 digits. |
%# | For str_to_date(), skip all numbers. |
%. | For str_to_date(), skip all punctation characters. |
%@ | For str_to_date(), skip all alpha characters. |
%% | A literal % character. |
Examples
--------
SELECT STR_TO_DATE('Wednesday, June 2, 2014', '%W, %M %e,
%Y');
+---------------------------------------------------------+
| STR_TO_DATE('Wednesday, June 2, 2014', '%W, %M %e,
%Y') |
+---------------------------------------------------------+
| 2014-06-02 |
+---------------------------------------------------------+
SELECT STR_TO_DATE('Wednesday23423, June 2, 2014', '%W,
%M %e, %Y');
+--------------------------------------------------------------+
| STR_TO_DATE('Wednesday23423, June 2, 2014', '%W, %M %e,
%Y') |
+--------------------------------------------------------------+
| NULL |
+--------------------------------------------------------------+
1 row in set, 1 warning (0.00 sec)
SHOW WARNINGS;
+---------+------+-----------------------------------------------------------------------------------+
| Level | Code | Message |
+---------+------+-----------------------------------------------------------------------------------+
| Warning | 1411 | Incorrect datetime value:
'Wednesday23423, June 2, 2014' for function str_to_date |
+---------+------+-----------------------------------------------------------------------------------+
SELECT STR_TO_DATE('Wednesday23423, June 2, 2014', '%W%#,
%M %e, %Y');
+----------------------------------------------------------------+
| STR_TO_DATE('Wednesday23423, June 2, 2014', '%W%#, %M
%e, %Y') |
+----------------------------------------------------------------+
| 2014-06-02 |
+----------------------------------------------------------------+
URL: https://mariadb.com/kb/en/str_to_date/https://mariadb.com/kb/en/str_to_date/ � � " SUBDATESyntax
------
SUBDATE(date,INTERVAL expr unit), SUBDATE(expr,days)
Description
-----------
When invoked with the INTERVAL form of the second argument,
SUBDATE()
is a synonym for DATE_SUB(). See Date and Time Units for a
complete list of permitted units.
The second form allows the use of an integer value for days.
In such
cases, it is interpreted as the number of days to be
subtracted from
the date or datetime expression expr.
Examples
--------
SELECT DATE_SUB('2008-01-02', INTERVAL 31 DAY);
+-----------------------------------------+
| DATE_SUB('2008-01-02', INTERVAL 31 DAY) |
+-----------------------------------------+
| 2007-12-02 |
+-----------------------------------------+
SELECT SUBDATE('2008-01-02', INTERVAL 31 DAY);
+----------------------------------------+
| SUBDATE('2008-01-02', INTERVAL 31 DAY) |
+----------------------------------------+
| 2007-12-02 |
+----------------------------------------+
SELECT SUBDATE('2008-01-02 12:00:00', 31);
+------------------------------------+
| SUBDATE('2008-01-02 12:00:00', 31) |
+------------------------------------+
| 2007-12-02 12:00:00 |
+------------------------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
("2007-01-30 21:31:07"),
("1983-10-15 06:42:51"),
("2011-04-21 12:34:56"),
("2011-10-30 06:31:41"),
("2011-01-30 14:03:25"),
("2004-10-07 11:19:34");
SELECT d, SUBDATE(d, 10) from t1;
+---------------------+---------------------+
| d | SUBDATE(d, 10) |
+---------------------+---------------------+
| 2007-01-30 21:31:07 | 2007-01-20 21:31:07 |
| 1983-10-15 06:42:51 | 1983-10-05 06:42:51 |
| 2011-04-21 12:34:56 | 2011-04-11 12:34:56 |
| 2011-10-30 06:31:41 | 2011-10-20 06:31:41 |
| 2011-01-30 14:03:25 | 2011-01-20 14:03:25 |
| 2004-10-07 11:19:34 | 2004-09-27 11:19:34 |
+---------------------+---------------------+
SELECT d, SUBDATE(d, INTERVAL 10 MINUTE) from t1;
+---------------------+--------------------------------+
| d | SUBDATE(d, INTERVAL 10 MINUTE) |
+---------------------+--------------------------------+
| 2007-01-30 21:31:07 | 2007-01-30 21:21:07 |
| 1983-10-15 06:42:51 | 1983-10-15 06:32:51 |
| 2011-04-21 12:34:56 | 2011-04-21 12:24:56 |
| 2011-10-30 06:31:41 | 2011-10-30 06:21:41 |
| 2011-01-30 14:03:25 | 2011-01-30 13:53:25 |
| 2004-10-07 11:19:34 | 2004-10-07 11:09:34 |
+---------------------+--------------------------------+
URL: https://mariadb.com/kb/en/subdate/https://mariadb.com/kb/en/subdate/ �� �F�A# ��
� �" SUBTIMESyntax
------
SUBTIME(expr1,expr2)
Description
-----------
SUBTIME() returns expr1 - expr2 expressed as a value in the
same
format as expr1. expr1 is a time or datetime expression, and
expr2 is
a time expression.
Examples
--------
SELECT SUBTIME('2007-12-31 23:59:59.999999','1
1:1:1.000002');
+--------------------------------------------------------+
| SUBTIME('2007-12-31 23:59:59.999999','1 1:1:1.000002')
|
+--------------------------------------------------------+
| 2007-12-30 22:58:58.999997 |
+--------------------------------------------------------+
SELECT SUBTIME('01:00:00.999999', '02:00:00.999998');
+-----------------------------------------------+
| SUBTIME('01:00:00.999999', '02:00:00.999998') |
+-----------------------------------------------+
| -00:59:59.999999 |
+-----------------------------------------------+
URL: https://mariadb.com/kb/en/subtime/https://mariadb.com/kb/en/subtime/ � # " SYSDATESyntax
------
SYSDATE([precision])
Description
-----------
Returns the current date and time as a value in 'YYYY-MM-DD
HH:MM:SS'
or YYYYMMDDHHMMSS.uuuuuu format, depending on whether the
function is
used in a string or numeric context.
The optional precision determines the microsecond precision.
See Microseconds in MariaDB.
SYSDATE() returns the time at which it executes. This
differs from the
behavior for NOW(), which returns a constant time that
indicates the
time at which the statement began to execute. (Within a
stored routine
or trigger, NOW() returns the time at which the routine or
triggering
statement began to execute.)
In addition, changing the timestamp system variable with a
SET timestamp statement affects the value returned by
NOW() but not by SYSDATE(). This means that timestamp
settings in the
binary log have no effect on invocations of SYSDATE().
Because SYSDATE() can return different values even within
the same
statement, and is not affected by SET TIMESTAMP, it is
non-deterministic and therefore unsafe for replication if
statement-based binary logging is used. If that is a
problem, you can
use row-based logging, or start the server with the mysqld
option --sysdate-is-now to cause SYSDATE() to be an alias
for NOW(). The non-deterministic nature of SYSDATE() also
means that indexes cannot be used for evaluating expressions
that refer to it, and that statements using the SYSDATE()
function are unsafe for statement-based replication.
Examples
--------
Difference between NOW() and SYSDATE():
SELECT NOW(), SLEEP(2), NOW();
+---------------------+----------+---------------------+
| NOW() | SLEEP(2) | NOW() |
+---------------------+----------+---------------------+
| 2010-03-27 13:23:40 | 0 | 2010-03-27 13:23:40 |
+---------------------+----------+---------------------+
SELECT SYSDATE(), SLEEP(2), SYSDATE();
+---------------------+----------+---------------------+
| SYSDATE() | SLEEP(2) | SYSDATE() |
+---------------------+----------+---------------------+
| 2010-03-27 13:23:52 | 0 | 2010-03-27 13:23:54 |
+---------------------+----------+---------------------+
With precision:
SELECT SYSDATE(4);
+--------------------------+
| SYSDATE(4) |
+--------------------------+
| 2018-07-10 10:17:13.1689 |
+--------------------------+
URL: https://mariadb.com/kb/en/sysdate/https://mariadb.com/kb/en/sysdate/ # TIMEDIFFSyntax
------
TIMEDIFF(expr1,expr2)
Description
-----------
TIMEDIFF() returns expr1 - expr2 expressed as a time value.
expr1 and
expr2 are time or date-and-time expressions, but both must
be of the
same type.
Examples
--------
SELECT TIMEDIFF('2000:01:01 00:00:00', '2000:01:01
00:00:00.000001');
+---------------------------------------------------------------+
| TIMEDIFF('2000:01:01 00:00:00', '2000:01:01
00:00:00.000001') |
+---------------------------------------------------------------+
| -00:00:00.000001 |
+---------------------------------------------------------------+
SELECT TIMEDIFF('2008-12-31 23:59:59.000001', '2008-12-30
01:01:01.000002');
+----------------------------------------------------------------------+
| TIMEDIFF('2008-12-31 23:59:59.000001', '2008-12-30
01:01:01.000002') |
+----------------------------------------------------------------------+
| 46:58:57.999999 |
+----------------------------------------------------------------------+
URL: https://mariadb.com/kb/en/timediff/https://mariadb.com/kb/en/timediff/ O- TIMESTAMP FUNCTIONSyntax
------
TIMESTAMP(expr), TIMESTAMP(expr1,expr2)
Description
-----------
With a single argument, this function returns the date or
datetime
expression expr as a datetime value. With two arguments, it
adds the
time expression expr2 to the date or datetime expression
expr1 and
returns the result as a datetime value.
Examples
--------
SELECT TIMESTAMP('2003-12-31');
+-------------------------+
| TIMESTAMP('2003-12-31') |
+-------------------------+
| 2003-12-31 00:00:00 |
+-------------------------+
SELECT TIMESTAMP('2003-12-31 12:00:00','6:30:00');
+--------------------------------------------+
| TIMESTAMP('2003-12-31 12:00:00','6:30:00') |
+--------------------------------------------+
| 2003-12-31 18:30:00 |
+--------------------------------------------+
URL: https://mariadb.com/kb/en/timestamp-function/https://mariadb.com/kb/en/timestamp-function/ k�#
H�Z ��~�r �� =' TIMESTAMPADDSyntax
------
TIMESTAMPADD(unit,interval,datetime_expr)
Description
-----------
Adds the integer expression interval to the date or datetime
expression datetime_expr. The unit for interval is given by
the unit
argument, which should be one of the following values:
MICROSECOND, SECOND, MINUTE, HOUR, DAY, WEEK, MONTH,
QUARTER, or YEAR.
The unit value may be specified using one of keywords as
shown, or
with a prefix of SQL_TSI_. For example, DAY and SQL_TSI_DAY
both are
legal.
Before MariaDB 5.5, FRAC_SECOND was permitted as a synonym
for MICROSECOND.
Examples
--------
SELECT TIMESTAMPADD(MINUTE,1,'2003-01-02');
+-------------------------------------+
| TIMESTAMPADD(MINUTE,1,'2003-01-02') |
+-------------------------------------+
| 2003-01-02 00:01:00 |
+-------------------------------------+
SELECT TIMESTAMPADD(WEEK,1,'2003-01-02');
+-----------------------------------+
| TIMESTAMPADD(WEEK,1,'2003-01-02') |
+-----------------------------------+
| 2003-01-09 |
+-----------------------------------+
URL: https://mariadb.com/kb/en/timestampadd/https://mariadb.com/kb/en/timestampadd/
�( TIMESTAMPDIFFSyntax
------
TIMESTAMPDIFF(unit,datetime_expr1,datetime_expr2)
Description
-----------
Returns datetime_expr2 - datetime_expr1, where
datetime_expr1 and
datetime_expr2 are date or datetime expressions. One
expression may be
a date and the other a datetime; a date value is treated as
a datetime
having the time part '00:00:00' where necessary. The unit
for the
result (an integer) is given by the unit argument. The legal
values
for unit are the same as those listed in the description of
the
TIMESTAMPADD() function, i.e MICROSECOND, SECOND, MINUTE,
HOUR, DAY, WEEK, MONTH, QUARTER, or YEAR.
TIMESTAMPDIFF can also be used to calculate age.
Examples
--------
SELECT TIMESTAMPDIFF(MONTH,'2003-02-01','2003-05-01');
+------------------------------------------------+
| TIMESTAMPDIFF(MONTH,'2003-02-01','2003-05-01') |
+------------------------------------------------+
| 3 |
+------------------------------------------------+
SELECT TIMESTAMPDIFF(YEAR,'2002-05-01','2001-01-01');
+-----------------------------------------------+
| TIMESTAMPDIFF(YEAR,'2002-05-01','2001-01-01') |
+-----------------------------------------------+
| -1 |
+-----------------------------------------------+
SELECT TIMESTAMPDIFF(MINUTE,'2003-02-01','2003-05-01
12:05:55');
+----------------------------------------------------------+
| TIMESTAMPDIFF(MINUTE,'2003-02-01','2003-05-01
12:05:55') |
+----------------------------------------------------------+
| 128885 |
+----------------------------------------------------------+
Calculating age:
SELECT CURDATE();
+------------+
| CURDATE() |
+------------+
| 2019-05-27 |
+------------+
SELECT TIMESTAMPDIFF(YEAR, '1971-06-06', CURDATE()) AS
age;
+------+
| age |
+------+
| 47 |
+------+
SELECT TIMESTAMPDIFF(YEAR, '1971-05-06', CURDATE()) AS
age;
+------+
| age |
+------+
| 48 |
+------+
Age as of 2014-08-02:
SELECT name, date_of_birth,
TIMESTAMPDIFF(YEAR,date_of_birth,'2014-08-02') AS age
FROM student_details;
+---------+---------------+------+
| name | date_of_birth | age |
+---------+---------------+------+
| Chun | 1993-12-31 | 20 |
| Esben | 1946-01-01 | 68 |
| Kaolin | 1996-07-16 | 18 |
| Tatiana | 1988-04-13 | 26 |
+---------+---------------+------+
URL: https://mariadb.com/kb/en/timestampdiff/https://mariadb.com/kb/en/timestampdiff/ �" TO_DAYSSyntax
------
TO_DAYS(date)
Description
-----------
Given a date date, returns the number of days since the
start of the current calendar (0000-00-00).
The function is not designed for use with dates before the
advent of the Gregorian calendar in October 1582. Results
will not be reliable since it doesn't account for the lost
days when the calendar changed from the Julian calendar.
This is the converse of the FROM_DAYS() function.
Examples
--------
SELECT TO_DAYS('2007-10-07');
+-----------------------+
| TO_DAYS('2007-10-07') |
+-----------------------+
| 733321 |
+-----------------------+
SELECT TO_DAYS('0000-01-01');
+-----------------------+
| TO_DAYS('0000-01-01') |
+-----------------------+
| 1 |
+-----------------------+
SELECT TO_DAYS(950501);
+-----------------+
| TO_DAYS(950501) |
+-----------------+
| 728779 |
+-----------------+
URL: https://mariadb.com/kb/en/to_days/https://mariadb.com/kb/en/to_days/
#% TO_SECONDSSyntax
------
TO_SECONDS(expr)
Description
-----------
Returns the number of seconds from year 0 till expr, or NULL
if expr is not a valid date or datetime.
Examples
--------
SELECT TO_SECONDS('2013-06-13');
+--------------------------+
| TO_SECONDS('2013-06-13') |
+--------------------------+
| 63538300800 |
+--------------------------+
SELECT TO_SECONDS('2013-06-13 21:45:13');
+-----------------------------------+
| TO_SECONDS('2013-06-13 21:45:13') |
+-----------------------------------+
| 63538379113 |
+-----------------------------------+
SELECT TO_SECONDS(NOW());
+-------------------+
| TO_SECONDS(NOW()) |
+-------------------+
| 63543530875 |
+-------------------+
SELECT TO_SECONDS(20130513);
+----------------------+
| TO_SECONDS(20130513) |
+----------------------+
| 63535622400 |
+----------------------+
1 row in set (0.00 sec)
SELECT TO_SECONDS(130513);
+--------------------+
| TO_SECONDS(130513) |
+--------------------+
| 63535622400 |
+--------------------+
URL: https://mariadb.com/kb/en/to_seconds/https://mariadb.com/kb/en/to_seconds/ �`�
��7 ~�L1 �� i ) UNIX_TIMESTAMPSyntax
------
UNIX_TIMESTAMP()
UNIX_TIMESTAMP(date)
Description
-----------
If called with no argument, returns a Unix timestamp
(seconds since
'1970-01-01 00:00:00' UTC) as an unsigned integer. If
UNIX_TIMESTAMP()
is called with a date argument, it returns the value of the
argument as seconds
since '1970-01-01 00:00:00' UTC. date may be a DATE
string, a
DATETIME string, a TIMESTAMP, or a number in
the format YYMMDD or YYYYMMDD. The server interprets date as
a value in the
current time zone and converts it to an internal value in
UTC. Clients can set
their time zone as described in time zones.
The inverse function of UNIX_TIMESTAMP() is FROM_UNIXTIME()
UNIX_TIMESTAMP() supports microseconds.
Timestamps in MariaDB have a maximum value of 2147483647,
equivalent to 2038-01-19 05:14:07. This is due to the
underlying 32-bit limitation. Using the function on a date
beyond this will result in NULL being returned. Use DATETIME
as a storage type if you require dates beyond this.
Error Handling
Returns NULL for wrong arguments to UNIX_TIMESTAMP(). In
MySQL and MariaDB before 5.3 wrong arguments to
UNIX_TIMESTAMP() returned 0.
Compatibility
As you can see in the examples above,
UNIX_TIMESTAMP(constant-date-string) returns a timestamp
with 6 decimals while MariaDB 5.2 and before returns it
without decimals. This can cause a problem if you are using
UNIX_TIMESTAMP() as a partitioning function. You can fix
this by using FLOOR(UNIX_TIMESTAMP(..)) or changing the date
string to a date number, like 20080101000000.
Examples
--------
SELECT UNIX_TIMESTAMP();
+------------------+
| UNIX_TIMESTAMP() |
+------------------+
| 1269711082 |
+------------------+
SELECT UNIX_TIMESTAMP('2007-11-30 10:30:19');
+---------------------------------------+
| UNIX_TIMESTAMP('2007-11-30 10:30:19') |
+---------------------------------------+
| 1196436619.000000 |
+---------------------------------------+
SELECT UNIX_TIMESTAMP("2007-11-30 10:30:19.123456");
+----------------------------------------------+
| unix_timestamp("2007-11-30 10:30:19.123456") |
+----------------------------------------------+
| 1196411419.123456 |
+----------------------------------------------+
SELECT FROM_UNIXTIME(UNIX_TIMESTAMP('2007-11-30
10:30:19'));
+------------------------------------------------------+
| FROM_UNIXTIME(UNIX_TIMESTAMP('2007-11-30 10:30:19')) |
+------------------------------------------------------+
| 2007-11-30 10:30:19.000000 |
+------------------------------------------------------+
SELECT FROM_UNIXTIME(FLOOR(UNIX_TIMESTAMP('2007-11-30
10:30:19')));
+-------------------------------------------------------------+
| FROM_UNIXTIME(FLOOR(UNIX_TIMESTAMP('2007-11-30
10:30:19'))) |
+-------------------------------------------------------------+
| 2007-11-30 10:30:19 |
+-------------------------------------------------------------+
URL: https://mariadb.com/kb/en/unix_timestamp/https://mariadb.com/kb/en/unix_timestamp/
y( UTC_TIMESTAMPSyntax
------
UTC_TIMESTAMP
UTC_TIMESTAMP([precision])
Description
-----------
Returns the current UTC date and time as a value in
'YYYY-MM-DD
HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on
whether the
function is used in a string or numeric context.
The optional precision determines the microsecond precision.
See Microseconds in MariaDB.
Examples
--------
SELECT UTC_TIMESTAMP(), UTC_TIMESTAMP() + 0;
+---------------------+-----------------------+
| UTC_TIMESTAMP() | UTC_TIMESTAMP() + 0 |
+---------------------+-----------------------+
| 2010-03-27 17:33:16 | 20100327173316.000000 |
+---------------------+-----------------------+
With precision:
SELECT UTC_TIMESTAMP(4);
+--------------------------+
| UTC_TIMESTAMP(4) |
+--------------------------+
| 2018-07-10 07:51:09.1019 |
+--------------------------+
URL: https://mariadb.com/kb/en/utc_timestamp/https://mariadb.com/kb/en/utc_timestamp/ � WEEKSyntax
------
WEEK(date[,mode])
Description
-----------
This function returns the week number for date. The
two-argument form of
WEEK() allows you to specify whether the week starts on
Sunday or Monday
and whether the return value should be in the range from 0
to 53 or from 1 to
53. If the mode argument is omitted, the value of the
default_week_format system variable is used.
Modes
Mode | 1st day of week | Range | Week 1 is the 1st week with
|
0 | Sunday | 0-53 | a Sunday in this year |
1 | Monday | 0-53 | more than 3 days this year |
2 | Sunday | 1-53 | a Sunday in this year |
3 | Monday | 1-53 | more than 3 days this year |
4 | Sunday | 0-53 | more than 3 days this year |
5 | Monday | 0-53 | a Monday in this year |
6 | Sunday | 1-53 | more than 3 days this year |
7 | Monday | 1-53 | a Monday in this year |
Examples
--------
SELECT WEEK('2008-02-20');
+--------------------+
| WEEK('2008-02-20') |
+--------------------+
| 7 |
+--------------------+
SELECT WEEK('2008-02-20',0);
+----------------------+
| WEEK('2008-02-20',0) |
+----------------------+
| 7 |
+----------------------+
SELECT WEEK('2008-02-20',1);
+----------------------+
| WEEK('2008-02-20',1) |
+----------------------+
| 8 |
+----------------------+
SELECT WEEK('2008-12-31',0);
+----------------------+
| WEEK('2008-12-31',0) |
+----------------------+
| 52 |
+----------------------+
SELECT WEEK('2008-12-31',1);
+----------------------+
| WEEK('2008-12-31',1) |
+----------------------+
| 53 |
+----------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
("2007-01-30 21:31:07"),
("1983-10-15 06:42:51"),
("2011-04-21 12:34:56"),
("2011-10-30 06:31:41"),
("2011-01-30 14:03:25"),
("2004-10-07 11:19:34");
SELECT d, WEEK(d,0), WEEK(d,1) from t1;
+---------------------+-----------+-----------+
| d | WEEK(d,0) | WEEK(d,1) |
+---------------------+-----------+-----------+
| 2007-01-30 21:31:07 | 4 | 5 |
| 1983-10-15 06:42:51 | 41 | 41 |
| 2011-04-21 12:34:56 | 16 | 16 |
| 2011-10-30 06:31:41 | 44 | 43 |
| 2011-01-30 14:03:25 | 5 | 4 |
| 2004-10-07 11:19:34 | 40 | 41 |
+---------------------+-----------+-----------+
URL: https://mariadb.com/kb/en/week/https://mariadb.com/kb/en/week/ v�� � � ��-� �
" WEEKDAYSyntax
------
WEEKDAY(date)
Description
-----------
Returns the weekday index for date
(0 = Monday, 1 = Tuesday, ... 6 = Sunday).
This contrasts with DAYOFWEEK() which follows the ODBC
standard
(1 = Sunday, 2 = Monday, ..., 7 = Saturday).
Examples
--------
SELECT WEEKDAY('2008-02-03 22:23:00');
+--------------------------------+
| WEEKDAY('2008-02-03 22:23:00') |
+--------------------------------+
| 6 |
+--------------------------------+
SELECT WEEKDAY('2007-11-06');
+-----------------------+
| WEEKDAY('2007-11-06') |
+-----------------------+
| 1 |
+-----------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
("2007-01-30 21:31:07"),
("1983-10-15 06:42:51"),
("2011-04-21 12:34:56"),
("2011-10-30 06:31:41"),
("2011-01-30 14:03:25"),
("2004-10-07 11:19:34");
SELECT d FROM t1 where WEEKDAY(d) = 6;
+---------------------+
| d |
+---------------------+
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
+---------------------+
URL: https://mariadb.com/kb/en/weekday/https://mariadb.com/kb/en/weekday/
>% WEEKOFYEARSyntax
------
WEEKOFYEAR(date)
Description
-----------
Returns the calendar week of the date as a number in the
range from 1
to 53. WEEKOFYEAR() is a compatibility function that is
equivalent to
WEEK(date,3).
Examples
--------
SELECT WEEKOFYEAR('2008-02-20');
+--------------------------+
| WEEKOFYEAR('2008-02-20') |
+--------------------------+
| 8 |
+--------------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
("2007-01-30 21:31:07"),
("1983-10-15 06:42:51"),
("2011-04-21 12:34:56"),
("2011-10-30 06:31:41"),
("2011-01-30 14:03:25"),
("2004-10-07 11:19:34");
select * from t1;
+---------------------+
| d |
+---------------------+
| 2007-01-30 21:31:07 |
| 1983-10-15 06:42:51 |
| 2011-04-21 12:34:56 |
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
| 2004-10-07 11:19:34 |
+---------------------+
SELECT d, WEEKOFYEAR(d), WEEK(d,3) from t1;
+---------------------+---------------+-----------+
| d | WEEKOFYEAR(d) | WEEK(d,3) |
+---------------------+---------------+-----------+
| 2007-01-30 21:31:07 | 5 | 5 |
| 1983-10-15 06:42:51 | 41 | 41 |
| 2011-04-21 12:34:56 | 16 | 16 |
| 2011-10-30 06:31:41 | 43 | 43 |
| 2011-01-30 14:03:25 | 4 | 4 |
| 2004-10-07 11:19:34 | 41 | 41 |
+---------------------+---------------+-----------+
URL: https://mariadb.com/kb/en/weekofyear/https://mariadb.com/kb/en/weekofyear/ � YEARSyntax
------
YEAR(date)
Description
-----------
Returns the year for the given date, in the range 1000 to
9999, or 0 for the
"zero" date.
Examples
--------
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
("2007-01-30 21:31:07"),
("1983-10-15 06:42:51"),
("2011-04-21 12:34:56"),
("2011-10-30 06:31:41"),
("2011-01-30 14:03:25"),
("2004-10-07 11:19:34");
SELECT * FROM t1;
+---------------------+
| d |
+---------------------+
| 2007-01-30 21:31:07 |
| 1983-10-15 06:42:51 |
| 2011-04-21 12:34:56 |
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
| 2004-10-07 11:19:34 |
+---------------------+
SELECT * FROM t1 WHERE YEAR(d) = 2011;
+---------------------+
| d |
+---------------------+
| 2011-04-21 12:34:56 |
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
+---------------------+
SELECT YEAR('1987-01-01');
+--------------------+
| YEAR('1987-01-01') |
+--------------------+
| 1987 |
+--------------------+
URL: https://mariadb.com/kb/en/year/https://mariadb.com/kb/en/year/ �# YEARWEEKSyntax
------
YEARWEEK(date), YEARWEEK(date,mode)
Description
-----------
Returns year and week for a date. The mode argument works
exactly like the mode
argument to WEEK(). The year in the result may be different
from the
year in the date argument for the first and the last week of
the year.
Examples
--------
SELECT YEARWEEK('1987-01-01');
+------------------------+
| YEARWEEK('1987-01-01') |
+------------------------+
| 198652 |
+------------------------+
CREATE TABLE t1 (d DATETIME);
INSERT INTO t1 VALUES
("2007-01-30 21:31:07"),
("1983-10-15 06:42:51"),
("2011-04-21 12:34:56"),
("2011-10-30 06:31:41"),
("2011-01-30 14:03:25"),
("2004-10-07 11:19:34");
SELECT * FROM t1;
+---------------------+
| d |
+---------------------+
| 2007-01-30 21:31:07 |
| 1983-10-15 06:42:51 |
| 2011-04-21 12:34:56 |
| 2011-10-30 06:31:41 |
| 2011-01-30 14:03:25 |
| 2004-10-07 11:19:34 |
+---------------------+
6 rows in set (0.02 sec)
SELECT YEARWEEK(d) FROM t1 WHERE YEAR(d) = 2011;
+-------------+
| YEARWEEK(d) |
+-------------+
| 201116 |
| 201144 |
| 201105 |
+-------------+
3 rows in set (0.03 sec)
URL: https://mariadb.com/kb/en/yearweek/https://mariadb.com/kb/en/yearweek/ �7 Well-Known Binary (WKB) FormatWKB stands for Well-Known Binary, a format for representing
geographical and geometrical data.
WKB uses 1-byte unsigned integers, 4-byte unsigned integers,
and 8-byte double-precision numbers.
The first byte indicates the byte order. 00 for big endian,
or 01 for little endian.
The next 4 bytes indicate the geometry type. Values from 1
to 7 indicate whether the type is Point, LineString,
Polygon, MultiPoint, MultiLineString, MultiPolygon, or
GeometryCollection respectively.
The 8-byte floats represent the co-ordinates.
Take the following example, a sequence of 21 bytes each
represented by two hex digits:
000000000140000000000000004010000000000000
It's big endian
000000000140000000000000004010000000000000
It's a POINT
000000000140000000000000004010000000000000
The X co-ordinate is 2.0
000000000140000000000000004010000000000000
The Y-co-ordinate is 4.0
000000000140000000000000004010000000000000
URL: https://mariadb.com/kb/en/well-known-binary-wkb-format/https://mariadb.com/kb/en/well-known-binary-wkb-format/ �I�
�� I{ =�'� �2 �' MPolyFromWKBSyntax
------
MPolyFromWKB(wkb[,srid])
MultiPolygonFromWKB(wkb[,srid])
Description
-----------
Constructs a MULTIPOLYGON value using its WKB representation
and SRID.
MPolyFromWKB() and MultiPolygonFromWKB() are synonyms.
Examples
--------
SET @g = ST_AsBinary(MPointFromText('MULTIPOLYGON(((28
26,28 0,84 0,84 42,28 26),(52 18,66 23,73 9,48 6,52
18)),((59 18,67 18,67 13,59 13,59 18)))'));
SELECT ST_AsText(MPolyFromWKB(@g));
+---------------------------------------------------------------------------------------------------------------+
| ST_AsText(MPolyFromWKB(@g)) |
+---------------------------------------------------------------------------------------------------------------+
| MULTIPOLYGON(((28 26,28 0,84 0,84 42,28 26),(52 18,66
23,73 9,48 6,52 18)),((59 18,67 18,67 13,59 13,59 18))) |
+---------------------------------------------------------------------------------------------------------------+
URL: https://mariadb.com/kb/en/mpolyfromwkb/https://mariadb.com/kb/en/mpolyfromwkb/ % �- ST_GeomCollFromWKBSyntax
------
ST_GeomCollFromWKB(wkb[,srid])
ST_GeometryCollectionFromWKB(wkb[,srid])
GeomCollFromWKB(wkb[,srid])
GeometryCollectionFromWKB(wkb[,srid])
Description
-----------
Constructs a GEOMETRYCOLLECTION value using its WKB
representation and SRID.
ST_GeomCollFromWKB(), ST_GeometryCollectionFromWKB(),
GeomCollFromWKB() and GeometryCollectionFromWKB() are
synonyms.
Examples
--------
SET @g =
ST_AsBinary(ST_GeomFromText('GEOMETRYCOLLECTION(POLYGON((5
5,10 5,10 10,5 5)),POINT(10 10))'));
SELECT ST_AsText(ST_GeomCollFromWKB(@g));
+----------------------------------------------------------------+
| ST_AsText(ST_GeomCollFromWKB(@g)) |
+----------------------------------------------------------------+
| GEOMETRYCOLLECTION(POLYGON((5 5,10 5,10 10,5 5)),POINT(10
10)) |
+----------------------------------------------------------------+
URL: https://mariadb.com/kb/en/st_geomcollfromwkb/https://mariadb.com/kb/en/st_geomcollfromwkb/ 9 ~& $ ST_BOUNDARYThe ST_BOUNDARY function was introduced in MariaDB 10.1.2
Syntax
------
ST_BOUNDARY(g)
BOUNDARY(g)
Description
-----------
Returns a geometry that is the closure of the combinatorial
boundary of the geometry value g.
BOUNDARY() is a synonym.
Examples
--------
SELECT ST_AsText(ST_Boundary(ST_GeomFromText('LINESTRING(3
3,0 0, -3 3)')));
+----------------------------------------------------------------------+
| ST_AsText(ST_Boundary(ST_GeomFromText('LINESTRING(3 3,0
0, -3 3)'))) |
+----------------------------------------------------------------------+
| MULTIPOINT(3 3,-3 3) |
+----------------------------------------------------------------------+
SELECT ST_AsText(ST_Boundary(ST_GeomFromText('POLYGON((3
3,0 0, -3 3, 3 3))')));
+--------------------------------------------------------------------------+
| ST_AsText(ST_Boundary(ST_GeomFromText('POLYGON((3 3,0 0,
-3 3, 3 3))'))) |
+--------------------------------------------------------------------------+
| LINESTRING(3 3,0 0,-3 3,3 3) |
+--------------------------------------------------------------------------+
URL: https://mariadb.com/kb/en/st_boundary/https://mariadb.com/kb/en/st_boundary/ ; & $ ST_ENVELOPESyntax
------
ST_ENVELOPE(g)
ENVELOPE(g)
Description
-----------
Returns the Minimum Bounding Rectangle (MBR) for the
geometry value g. The result is returned as a Polygon value.
The polygon is defined by the corner points of the bounding
box:
POLYGON((MINX MINY, MAXX MINY, MAXX MAXY, MINX MAXY, MINX
MINY))
ST_ENVELOPE() and ENVELOPE() are synonyms.
Examples
--------
SELECT AsText(ST_ENVELOPE(GeomFromText('LineString(1 1,4
4)')));
+----------------------------------------------------------+
| AsText(ST_ENVELOPE(GeomFromText('LineString(1 1,4 4)')))
|
+----------------------------------------------------------+
| POLYGON((1 1,4 1,4 4,1 4,1 1)) |
+----------------------------------------------------------+
URL: https://mariadb.com/kb/en/st_envelope/https://mariadb.com/kb/en/st_envelope/ > Y& $ ST_ISCLOSEDSyntax
------
ST_IsClosed(g)
IsClosed(g)
Description
-----------
Returns 1 if a given LINESTRING's start and end points are
the same, or 0 if they are not the same. Before MariaDB
10.1.5, returns NULL if not given a LINESTRING. After
MariaDB 10.1.5, returns -1.
ST_IsClosed() and IsClosed() are synonyms.
Examples
--------
SET @ls = 'LineString(0 0, 0 4, 4 4, 0 0)';
SELECT ST_ISCLOSED(GEOMFROMTEXT(@ls));
+--------------------------------+
| ST_ISCLOSED(GEOMFROMTEXT(@ls)) |
+--------------------------------+
| 1 |
+--------------------------------+
SET @ls = 'LineString(0 0, 0 4, 4 4, 0 1)';
SELECT ST_ISCLOSED(GEOMFROMTEXT(@ls));
+--------------------------------+
| ST_ISCLOSED(GEOMFROMTEXT(@ls)) |
+--------------------------------+
| 0 |
+--------------------------------+
URL: https://mariadb.com/kb/en/st_isclosed/https://mariadb.com/kb/en/st_isclosed/ �� S�(� �5D) �� G u* % BINARY OperatorSyntax
------
BINARY
Description
-----------
The BINARY operator casts the string following it to a
binary string. This is an easy way to force a column
comparison to be done byte by byte rather than character by
character. This causes the comparison to be case sensitive
even if the column isn't defined as BINARY or BLOB.
BINARY also causes trailing spaces to be significant.
Examples
--------
SELECT 'a' = 'A';
+-----------+
| 'a' = 'A' |
+-----------+
| 1 |
+-----------+
SELECT BINARY 'a' = 'A';
+------------------+
| BINARY 'a' = 'A' |
+------------------+
| 0 |
+------------------+
SELECT 'a' = 'a ';
+------------+
| 'a' = 'a ' |
+------------+
| 1 |
+------------+
SELECT BINARY 'a' = 'a ';
+-------------------+
| BINARY 'a' = 'a ' |
+-------------------+
| 0 |
+-------------------+
URL: https://mariadb.com/kb/en/binary-operator/https://mariadb.com/kb/en/binary-operator/ I v % CASTSyntax
------
CAST(expr AS type)
Description
-----------
The CAST() function takes a value of one type and produces a
value of another type, similar to the CONVERT() function.
For more information, see the description of CONVERT().
The main difference between the CAST() and CONVERT() is that
CONVERT(expr,type) is ODBC syntax while CAST(expr as type)
and CONVERT(... USING ...) are SQL92 syntax.
In MariaDB 10.4 and later, you can use the CAST() function
with the INTERVAL keyword.
Until MariaDB 5.5.31, X'HHHH', the standard SQL syntax for
binary string literals, erroneously worked in the same way
as 0xHHHH. In 5.5.31 it was intentionally changed to behave
as a string in all contexts (and never as a number).
This introduces an incompatibility with previous versions of
MariaDB, and all versions of MySQL (see the example below).
Examples
--------
Simple casts:
SELECT CAST("abc" AS BINARY);
SELECT CAST("1" AS UNSIGNED INTEGER);
SELECT CAST(123 AS CHAR CHARACTER SET utf8)
Note that when one casts to CHAR without specifying the
character set, the collation_connection character set
collation will be used. When used with CHAR CHARACTER SET,
the default collation for that character set will be used.
SELECT COLLATION(CAST(123 AS CHAR));
+------------------------------+
| COLLATION(CAST(123 AS CHAR)) |
+------------------------------+
| latin1_swedish_ci |
+------------------------------+
SELECT COLLATION(CAST(123 AS CHAR CHARACTER SET utf8));
+-------------------------------------------------+
| COLLATION(CAST(123 AS CHAR CHARACTER SET utf8)) |
+-------------------------------------------------+
| utf8_general_ci |
+-------------------------------------------------+
If you also want to change the collation, you have to use
the COLLATE operator:
SELECT COLLATION(CAST(123 AS CHAR CHARACTER SET utf8)
COLLATE utf8_unicode_ci);
+-------------------------------------------------------------------------+
| COLLATION(CAST(123 AS CHAR CHARACTER SET utf8) COLLATE
utf8_unicode_ci) |
+-------------------------------------------------------------------------+
| utf8_unicode_ci |
+-------------------------------------------------------------------------+
Using CAST() to order an ENUM field as a CHAR rather than
the internal numerical value:
CREATE TABLE enum_list (enum_field enum('c','a','b'));
INSERT INTO enum_list (enum_field)
VALUES('c'),('a'),('c'),('b');
SELECT * FROM enum_list
ORDER BY enum_field;
+------------+
| enum_field |
+------------+
| c |
| c |
| a |
| b |
+------------+
SELECT * FROM enum_list
ORDER BY CAST(enum_field AS CHAR);
+------------+
| enum_field |
+------------+
| a |
| b |
| c |
| c |
+------------+
From MariaDB 5.5.31, the following will trigger warnings,
since x'aa' and 'X'aa' no longer behave as a number.
Previously, and in all versions of MySQL, no warnings are
triggered since they did erroneously behave as a number:
SELECT CAST(0xAA AS UNSIGNED), CAST(x'aa' AS UNSIGNED),
CAST(X'aa' AS UNSIGNED);
+------------------------+-------------------------+-------------------------+
| CAST(0xAA AS UNSIGNED) | CAST(x'aa' AS UNSIGNED) |
CAST(X'aa' AS UNSIGNED) |
+------------------------+-------------------------+-------------------------+
| 170 | 0 | 0 |
+------------------------+-------------------------+-------------------------+
1 row in set, 2 warnings (0.00 sec)
Warning (Code 1292): Truncated incorrect INTEGER value:
'\xAA'
Warning (Code 1292): Truncated incorrect INTEGER value:
'\xAA'
Casting to intervals:
SELECT CAST(2019-01-04 INTERVAL AS DAY_SECOND(2)) AS
"Cast";
+-------------+
| Cast |
+-------------+
| 00:20:17.00 |
+-------------+
URL: https://mariadb.com/kb/en/cast/https://mariadb.com/kb/en/cast/ J
H( % CHAR FunctionSyntax
------
CHAR(N,... [USING charset_name])
Description
-----------
CHAR() interprets each argument as an INT and returns a
string consisting of the characters given by the code values
of those integers. NULL values are skipped. By default,
CHAR() returns a binary string. To produce a string in a
given character set, use the optional USING clause:
SELECT CHARSET(CHAR(0x65)), CHARSET(CHAR(0x65 USING utf8));
+---------------------+--------------------------------+
| CHARSET(CHAR(0x65)) | CHARSET(CHAR(0x65 USING utf8)) |
+---------------------+--------------------------------+
| binary | utf8 |
+---------------------+--------------------------------+
If USING is given and the result string is illegal for the
given character set, a warning is issued. Also, if strict
SQL mode is enabled, the result from CHAR() becomes NULL.
Examples
--------
SELECT CHAR(77,97,114,'105',97,'68',66);
+----------------------------------+
| CHAR(77,97,114,'105',97,'68',66) |
+----------------------------------+
| MariaDB |
+----------------------------------+
SELECT CHAR(77,77.3,'77.3');
+----------------------+
| CHAR(77,77.3,'77.3') |
+----------------------+
| MMM |
+----------------------+
1 row in set, 1 warning (0.00 sec)
Warning (Code 1292): Truncated incorrect INTEGER value:
'77.3'
URL: https://mariadb.com/kb/en/char-function/https://mariadb.com/kb/en/char-function/ o��� ��
�� �� L & % CHAR_LENGTHSyntax
------
CHAR_LENGTH(str)
Description
-----------
Returns the length of the given string argument, measured in
characters. A multi-byte character counts as a single
character. This means that for a string containing five
two-byte characters, LENGTH() (or OCTET_LENGTH() in Oracle
mode) returns 10, whereas CHAR_LENGTH() returns 5. If the
argument is NULL, it returns NULL.
If the argument is not a string value, it is converted into
a string.
It is synonymous with the CHARACTER_LENGTH() function.
Until MariaDB 10.3.1, returns MYSQL_TYPE_LONGLONG, or
bigint(10), in all cases. From MariaDB 10.3.1, returns
MYSQL_TYPE_LONG, or int(10), when the result would fit
within 32-bits.
Examples
--------
SELECT CHAR_LENGTH('MariaDB');
+------------------------+
| CHAR_LENGTH('MariaDB') |
+------------------------+
| 7 |
+------------------------+
SELECT CHAR_LENGTH('π');
+-------------------+
| CHAR_LENGTH('π') |
+-------------------+
| 1 |
+-------------------+
URL: https://mariadb.com/kb/en/char_length/https://mariadb.com/kb/en/char_length/ M � % CHRThe CHR() function was introduced in MariaDB 10.3.1 to
provide Oracle compatibility
Syntax
------
CHR(N)
Description
-----------
CHR() interprets each argument N as an integer and returns a
VARCHAR(1) string consisting of the character given by the
code values of the integer. The character set and collation
of the string are set according to the values of the
character_set_database and collation_database system
variables.
CHR() is similar to the CHAR() function, but only accepts a
single argument.
CHR() is available in all sql_modes.
Examples
--------
SELECT CHR(67);
+---------+
| CHR(67) |
+---------+
| C |
+---------+
SELECT CHR('67');
+-----------+
| CHR('67') |
+-----------+
| C |
+-----------+
SELECT CHR('C');
+----------+
| CHR('C') |
+----------+
| |
+----------+
1 row in set, 1 warning (0.000 sec)
SHOW WARNINGS;
+---------+------+----------------------------------------+
| Level | Code | Message |
+---------+------+----------------------------------------+
| Warning | 1292 | Truncated incorrect INTEGER value: 'C'
|
+---------+------+----------------------------------------+
URL: https://mariadb.com/kb/en/chr/https://mariadb.com/kb/en/chr/ N �! % CONCATSyntax
------
CONCAT(str1,str2,...)
Description
-----------
Returns the string that results from concatenating the
arguments. May have one or more arguments. If all arguments
are non-binary strings, the result is a non-binary string.
If the arguments include any binary strings, the result is a
binary string. A numeric argument is converted to its
equivalent binary string form; if you want to avoid that,
you can use an explicit type cast, as in this example:
SELECT CONCAT(CAST(int_col AS CHAR), char_col);
CONCAT() returns NULL if any argument is NULL.
A NULL parameter hides all information contained in other
parameters from the result. Sometimes this is not desirable;
to avoid this, you can:
Use the CONCAT_WS() function with an empty separator,
because that function is NULL-safe.
Use IFNULL() to turn NULLs into empty strings.
Oracle Mode
In Oracle mode from MariaDB 10.3, CONCAT ignores NULL.
Examples
--------
SELECT CONCAT('Ma', 'ria', 'DB');
+---------------------------+
| CONCAT('Ma', 'ria', 'DB') |
+---------------------------+
| MariaDB |
+---------------------------+
SELECT CONCAT('Ma', 'ria', NULL, 'DB');
+---------------------------------+
| CONCAT('Ma', 'ria', NULL, 'DB') |
+---------------------------------+
| NULL |
+---------------------------------+
SELECT CONCAT(42.0);
+--------------+
| CONCAT(42.0) |
+--------------+
| 42.0 |
+--------------+
Using IFNULL() to handle NULLs:
SELECT CONCAT('The value of @v is: ', IFNULL(@v, ''));
+------------------------------------------------+
| CONCAT('The value of @v is: ', IFNULL(@v, '')) |
+------------------------------------------------+
| The value of @v is: |
+------------------------------------------------+
In Oracle mode, from MariaDB 10.3:
SELECT CONCAT('Ma', 'ria', NULL, 'DB');
+---------------------------------+
| CONCAT('Ma', 'ria', NULL, 'DB') |
+---------------------------------+
| MariaDB |
+---------------------------------+
URL: https://mariadb.com/kb/en/concat/https://mariadb.com/kb/en/concat/ O �$ % CONCAT_WSSyntax
------
CONCAT_WS(separator,str1,str2,...)
Description
-----------
CONCAT_WS() stands for Concatenate With Separator and is a
special form of CONCAT(). The first argument is the
separator for the rest of the arguments. The separator is
added between the strings to be concatenated. The separator
can be a string, as can the rest of the arguments.
If the separator is NULL, the result is NULL; all other NULL
values are skipped. This makes CONCAT_WS() suitable when you
want to concatenate some values and avoid losing all
information if one of them is NULL.
Examples
--------
SELECT CONCAT_WS(',','First name','Second name','Last
Name');
+-------------------------------------------------------+
| CONCAT_WS(',','First name','Second name','Last
Name') |
+-------------------------------------------------------+
| First name,Second name,Last Name |
+-------------------------------------------------------+
SELECT CONCAT_WS('-','Floor',NULL,'Room');
+------------------------------------+
| CONCAT_WS('-','Floor',NULL,'Room') |
+------------------------------------+
| Floor-Room |
+------------------------------------+
In some cases, remember to include a space in the separator
string:
SET @a = 'gnu', @b = 'penguin', @c = 'sea lion';
Query OK, 0 rows affected (0.00 sec)
SELECT CONCAT_WS(', ', @a, @b, @c);
+-----------------------------+
| CONCAT_WS(', ', @a, @b, @c) |
+-----------------------------+
| gnu, penguin, sea lion |
+-----------------------------+
Using CONCAT_WS() to handle NULLs:
SET @a = 'a', @b = NULL, @c = 'c';
SELECT CONCAT_WS('', @a, @b, @c);
+---------------------------+
| CONCAT_WS('', @a, @b, @c) |
+---------------------------+
| ac |
+---------------------------+
URL: https://mariadb.com/kb/en/concat_ws/https://mariadb.com/kb/en/concat_ws/ ( P� D�@3 �� P A" % CONVERTSyntax
------
CONVERT(expr,type), CONVERT(expr USING transcoding_name)
Description
-----------
The CONVERT() and CAST() functions take a value of one type
and produce a value of another type.
The type can be one of the following values:
BINARY
CHAR
DATE
DATETIME
DECIMAL[(M[,D])]
DOUBLE
FLOAT — From MariaDB 10.4.5
INTEGER
Short for SIGNED INTEGER
SIGNED [INTEGER]
TIME
UNSIGNED [INTEGER]
Note that in MariaDB, INT and INTEGER are the same thing.
BINARY produces a string with the BINARY data type. If the
optional length is given, BINARY(N) causes the cast to use
no more than N bytes of the argument. Values shorter than
the given number in bytes are padded with 0x00 bytes to make
them equal the length value.
CHAR(N) causes the cast to use no more than the number of
characters given in the argument.
The main difference between the CAST() and CONVERT() is that
CONVERT(expr,type) is ODBC syntax while CAST(expr as type)
and CONVERT(... USING ...) are SQL92 syntax.
CONVERT() with USING is used to convert data between
different character sets. In MariaDB, transcoding names are
the same as the
corresponding character set names. For example, this
statement
converts the string 'abc' in the default character set to
the
corresponding string in the utf8 character set:
SELECT CONVERT('abc' USING utf8);
Examples
--------
SELECT enum_col FROM tbl_name
ORDER BY CAST(enum_col AS CHAR);
Converting a BINARY to string to permit the LOWER function
to work:
SET @x = 'AardVark';
SET @x = BINARY 'AardVark';
SELECT LOWER(@x), LOWER(CONVERT (@x USING latin1));
+-----------+----------------------------------+
| LOWER(@x) | LOWER(CONVERT (@x USING latin1)) |
+-----------+----------------------------------+
| AardVark | aardvark |
+-----------+----------------------------------+
URL: https://mariadb.com/kb/en/convert/https://mariadb.com/kb/en/convert/ Q % ELTSyntax
------
ELT(N, str1[, str2, str3,...])
Description
-----------
Takes a numeric argument and a series of string arguments.
Returns the string that corresponds to the given numeric
position. For instance, it returns str1 if N is 1, str2 if N
is 2, and so on. If the numeric argument is a FLOAT, MariaDB
rounds it to the nearest INTEGER. If the numeric argument is
less than 1, greater than the total number of arguments, or
not a number, ELT() returns NULL. It must have at least two
arguments.
It is complementary to the FIELD() function.
Examples
--------
SELECT ELT(1, 'ej', 'Heja', 'hej', 'foo');
+------------------------------------+
| ELT(1, 'ej', 'Heja', 'hej', 'foo') |
+------------------------------------+
| ej |
+------------------------------------+
SELECT ELT(4, 'ej', 'Heja', 'hej', 'foo');
+------------------------------------+
| ELT(4, 'ej', 'Heja', 'hej', 'foo') |
+------------------------------------+
| foo |
+------------------------------------+
URL: https://mariadb.com/kb/en/elt/https://mariadb.com/kb/en/elt/ R
,% % EXPORT_SETSyntax
------
EXPORT_SET(bits, on, off[, separator[, number_of_bits]])
Description
-----------
Takes a minimum of three arguments. Returns a string where
each bit in the given bits argument is returned, with the
string values given for on and off.
Bits are examined from right to left, (from low-order to
high-order bits). Strings are added to the result from left
to right, separated by a separator string (defaults as
','). You can optionally limit the number of bits the
EXPORT_SET() function examines using the number_of_bits
option.
If any of the arguments are set as NULL, the function
returns NULL.
Examples
--------
SELECT EXPORT_SET(5,'Y','N',',',4);
+-----------------------------+
| EXPORT_SET(5,'Y','N',',',4) |
+-----------------------------+
| Y,N,Y,N |
+-----------------------------+
SELECT EXPORT_SET(6,'1','0',',',10);
+------------------------------+
| EXPORT_SET(6,'1','0',',',10) |
+------------------------------+
| 0,1,1,0,0,0,0,0,0,0 |
+------------------------------+
URL: https://mariadb.com/kb/en/export_set/https://mariadb.com/kb/en/export_set/ T � % FIELDSyntax
------
FIELD(pattern, str1[,str2,...])
Description
-----------
Returns the index position of the string or number matching
the given pattern. Returns 0 in the event that none of the
arguments match the pattern. Raises an Error 1582 if not
given at least two arguments.
When all arguments given to the FIELD() function are
strings, they are treated as case-insensitive. When all the
arguments are numbers, they are treated as numbers.
Otherwise, they are treated as doubles.
If the given pattern occurs more than once, the FIELD()
function only returns the index of the first instance. If
the given pattern is NULL, the function returns 0, as a NULL
pattern always fails to match.
This function is complementary to the ELT() function.
Examples
--------
SELECT FIELD('ej', 'Hej', 'ej', 'Heja', 'hej',
'foo')
AS 'Field Results';
+---------------+
| Field Results |
+---------------+
| 2 |
+---------------+
SELECT FIELD('fo', 'Hej', 'ej', 'Heja', 'hej',
'foo')
AS 'Field Results';
+---------------+
| Field Results |
+---------------+
| 0 |
+---------------+
SELECT FIELD(1, 2, 3, 4, 5, 1) AS 'Field Results';
+---------------+
| Field Results |
+---------------+
| 5 |
+---------------+
SELECT FIELD(NULL, 2, 3) AS 'Field Results';
+---------------+
| Field Results |
+---------------+
| 0 |
+---------------+
SELECT FIELD('fail') AS 'Field Results';
Error 1582 (42000): Incorrect parameter count in call
to native function 'field'
URL: https://mariadb.com/kb/en/field/https://mariadb.com/kb/en/field/ +,� i�> x� �. �` S ' % EXTRACTVALUESyntax
------
EXTRACTVALUE(xml_frag, xpath_expr)
Description
-----------
The EXTRACTVALUE() function takes two string arguments: a
fragment of XML markup and an XPath expression, (also known
as a locator). It returns the text (That is, CDDATA), of the
first text node which is a child of the element or elements
matching the XPath expression.
In cases where a valid XPath expression does not match any
text nodes in a valid XML fragment, (including the implicit
/text() expression), the EXTRACTVALUE() function returns an
empty string.
Invalid Arguments
When either the XML fragment or the XPath expression is
NULL, the EXTRACTVALUE() function returns NULL. When the XML
fragment is invalid, it raises a warning Code 1525:
Warning (Code 1525): Incorrect XML value: 'parse error at
line 1 pos 11: unexpected END-OF-INPUT'
When the XPath value is invalid, it generates an Error 1105:
ERROR 1105 (HY000): XPATH syntax error: ')'
Explicit text() Expressions
This function is the equivalent of performing a match using
the XPath expression after appending /text(). In other
words:
SELECT
EXTRACTVALUE('example', '/cases/case') AS 'Base
Example',
EXTRACTVALUE('example', '/cases/case/text()') AS
'text() Example';
+--------------+----------------+
| Base Example | text() Example |
+--------------+----------------+
| example | example |
+--------------+----------------+
Count Matches
When EXTRACTVALUE() returns multiple matches, it returns the
content of the first child text node of each matching
element, in the matched order, as a single, space-delimited
string.
By design, the EXTRACTVALUE() function makes no distinction
between a match on an empty element and no match at all. If
you need to determine whether no matching element was found
in the XML fragment or if an element was found that
contained no child text nodes, use the XPath count()
function.
For instance, when looking for a value that exists, but
contains no child text nodes, you would get a count of the
number of matching instances:
SELECT
EXTRACTVALUE('', '/cases/case') AS 'Empty Example',
EXTRACTVALUE('', '/cases/case/count()') AS 'count()
Example';
+---------------+-----------------+
| Empty Example | count() Example |
+---------------+-----------------+
| | 1 |
+---------------+-----------------+
Alternatively, when looking for a value that doesn't exist,
count() returns 0.
SELECT
EXTRACTVALUE('', '/cases/person') AS 'No Match
Example',
EXTRACTVALUE('', '/cases/person/count()') AS 'count()
Example';
+------------------+-----------------+
| No Match Example | count() Example |
+------------------+-----------------+
| | 0|
+------------------+-----------------+
Matches
Important: The EXTRACTVALUE() function only returns CDDATA.
It does not return tags that the element might contain or
the text that these child elements contain.
SELECT EXTRACTVALUE('Personx@example.com', '/cases') AS
Case;
+--------+
| Case |
+--------+
| Person |
+--------+
Note, in the above example, while the XPath expression
matches to the parent instance, it does not return the
contained tag or its content.
Examples
--------
SELECT
ExtractValue('cccddd', '/a') AS val1,
ExtractValue('cccddd', '/a/b') AS val2,
ExtractValue('cccddd', '//b') AS val3,
ExtractValue('cccddd', '/b') AS val4,
ExtractValue('cccdddeee', '//b') AS val5;
+------+------+------+------+---------+
| val1 | val2 | val3 | val4 | val5 |
+------+------+------+------+---------+
| ccc | ddd | ddd | | ddd eee |
+------+------+------+------+---------+
URL: https://mariadb.com/kb/en/extractvalue/https://mariadb.com/kb/en/extractvalue/ U Z& % FIND_IN_SETSyntax
------
FIND_IN_SET(pattern, strlist)
Description
-----------
Returns the index position where the given pattern occurs in
a string list. The first argument is the pattern you want to
search for. The second argument is a string containing
comma-separated variables. If the second argument is of the
SET data-type, the function is optimized to use bit
arithmetic.
If the pattern does not occur in the string list or if the
string list is an empty string, the function returns 0. If
either argument is NULL, the function returns NULL. The
function does not return the correct result if the pattern
contains a comma (",") character.
Examples
--------
SELECT FIND_IN_SET('b','a,b,c,d') AS "Found Results";
+---------------+
| Found Results |
+---------------+
| 2 |
+---------------+
URL: https://mariadb.com/kb/en/find_in_set/https://mariadb.com/kb/en/find_in_set/ V U! % FORMATSyntax
------
FORMAT(num, decimal_position[, locale])
Description
-----------
Formats the given number for display as a string, adding
separators to appropriate position and rounding the results
to the given decimal position. For instance, it would format
15233.345 to 15,233.35.
If the given decimal position is 0, it rounds to return no
decimal point or fractional part. You can optionally specify
a locale value to format numbers to the pattern appropriate
for the given region.
Examples
--------
SELECT FORMAT(1234567890.09876543210, 4) AS 'Format';
+--------------------+
| Format |
+--------------------+
| 1,234,567,890.0988 |
+--------------------+
SELECT FORMAT(1234567.89, 4) AS 'Format';
+----------------+
| Format |
+----------------+
| 1,234,567.8900 |
+----------------+
SELECT FORMAT(1234567.89, 0) AS 'Format';
+-----------+
| Format |
+-----------+
| 1,234,568 |
+-----------+
SELECT FORMAT(123456789,2,'rm_CH') AS 'Format';
+----------------+
| Format |
+----------------+
| 123'456'789,00 |
+----------------+
URL: https://mariadb.com/kb/en/format/https://mariadb.com/kb/en/format/ �m� aIo�, �� W K& % FROM_BASE64The FROM_BASE64() function was introduced in MariaDB 10.0.5.
Syntax
------
FROM_BASE64(str)
Description
-----------
Decodes the given base-64 encode string, returning the
result as a binary string. Returns NULL if the given string
is NULL or if it's invalid.
It is the reverse of the TO_BASE64 function.
There are numerous methods to base-64 encode a string.
MariaDB uses the following:
It encodes alphabet value 64 as '+'.
It encodes alphabet value 63 as '/'.
It codes output in groups of four printable characters. Each
three byte of data encoded uses four characters. If the
final group is incomplete, it pads the difference with the
'=' character.
It divides long output, adding a new line very 76
characters.
In decoding, it recognizes and ignores newlines, carriage
returns, tabs and space whitespace characters.
SELECT TO_BASE64('Maria') AS 'Input';
+-----------+
| Input |
+-----------+
| TWFyaWE= |
+-----------+
SELECT FROM_BASE64('TWFyaWE=') AS 'Output';
+--------+
| Output |
+--------+
| Maria |
+--------+
URL: https://mariadb.com/kb/en/from_base64/https://mariadb.com/kb/en/from_base64/ X ] % HEXSyntax
------
HEX(N_or_S)
Description
-----------
If N_or_S is a number, returns a string representation of
the hexadecimal
value of N, where N is a longlong (BIGINT) number. This is
equivalent to CONV(N,10,16).
If N_or_S is a string, returns a hexadecimal string
representation of
N_or_S where each byte of each character in N_or_S is
converted to two hexadecimal
digits. If N_or_S is NULL, returns NULL. The inverse of this
operation is performed by the UNHEX()
function.
Examples
--------
SELECT HEX(255);
+----------+
| HEX(255) |
+----------+
| FF |
+----------+
SELECT 0x4D617269614442;
+------------------+
| 0x4D617269614442 |
+------------------+
| MariaDB |
+------------------+
SELECT HEX('MariaDB');
+----------------+
| HEX('MariaDB') |
+----------------+
| 4D617269614442 |
+----------------+
URL: https://mariadb.com/kb/en/hex/https://mariadb.com/kb/en/hex/ Y u* % INSERT FunctionSyntax
------
INSERT(str,pos,len,newstr)
Description
-----------
Returns the string str, with the substring beginning at
position pos
and len characters long replaced by the string newstr.
Returns the
original string if pos is not within the length of the
string.
Replaces the rest of the string from position pos if len is
not within
the length of the rest of the string. Returns NULL if any
argument is
NULL.
Examples
--------
SELECT INSERT('Quadratic', 3, 4, 'What');
+-----------------------------------+
| INSERT('Quadratic', 3, 4, 'What') |
+-----------------------------------+
| QuWhattic |
+-----------------------------------+
SELECT INSERT('Quadratic', -1, 4, 'What');
+------------------------------------+
| INSERT('Quadratic', -1, 4, 'What') |
+------------------------------------+
| Quadratic |
+------------------------------------+
SELECT INSERT('Quadratic', 3, 100, 'What');
+-------------------------------------+
| INSERT('Quadratic', 3, 100, 'What') |
+-------------------------------------+
| QuWhat |
+-------------------------------------+
URL: https://mariadb.com/kb/en/insert-function/https://mariadb.com/kb/en/insert-function/ ] ;! % LENGTHSyntax
------
LENGTH(str)
Description
-----------
Returns the length of the string str, measured in bytes. A
multi-byte
character counts as multiple bytes. This means that for a
string
containing five two-byte characters, LENGTH() returns 10,
whereas
CHAR_LENGTH() returns 5.
If str is not a string value, it is converted into a string.
If str is NULL, the function returns NULL.
Until MariaDB 10.3.1, returns MYSQL_TYPE_LONGLONG, or
bigint(10), in all cases. From MariaDB 10.3.1, returns
MYSQL_TYPE_LONG, or int(10), when the result would fit
within 32-bits.
Oracle Mode
When running Oracle mode from MariaDB 10.3, LENGTH() is a
synonym for CHAR_LENGTH().
Examples
--------
SELECT LENGTH('MariaDB');
+-------------------+
| LENGTH('MariaDB') |
+-------------------+
| 7 |
+-------------------+
SELECT LENGTH('π');
+--------------+
| LENGTH('π') |
+--------------+
| 2 |
+--------------+
In Oracle mode from MariaDB 10.3:
SELECT LENGTH('π');
+--------------+
| LENGTH('π') |
+--------------+
| 1 |
+--------------+
URL: https://mariadb.com/kb/en/length/https://mariadb.com/kb/en/length/ ` �$ % LOAD_FILESyntax
------
LOAD_FILE(file_name)
Description
-----------
Reads the file and returns the file contents as a string. To
use this function, the file must be located on the server
host, you must specify the full path name to the file, and
you must have the FILE privilege. The file must be readable
by all and it must be less than the size, in bytes, of the
max_allowed_packet system variable. If the secure_file_priv
system variable is set to a non-empty directory name, the
file to be loaded must be located in that directory.
If the file does not exist or cannot be read because one of
the preceding conditions is not satisfied, the function
returns NULL.
Since MariaDB 5.1, the character_set_filesystem system
variable has controlled interpretation of file names that
are given as literal strings.
Statements using the LOAD_FILE() function are not safe for
statement based replication. This is because the slave will
execute the LOAD_FILE() command itself. If the file doesn't
exist on the slave, the function will return NULL.
Examples
--------
UPDATE t SET blob_col=LOAD_FILE('/tmp/picture') WHERE
id=1;
URL: https://mariadb.com/kb/en/load_file/https://mariadb.com/kb/en/load_file/ N�� p"��� �4_�. ��
_ � % LIKESyntax
------
expr LIKE pat [ESCAPE 'escape_char']
expr NOT LIKE pat [ESCAPE 'escape_char']
Description
-----------
Tests whether expr matches the pattern pat. Returns either 1
(TRUE) or 0 (FALSE).
Both expr and pat may be any valid expression and are
evaluated to strings.
Patterns may use the following wildcard characters:
% matches any number of characters, including zero.
_ matches any single character.
Use NOT LIKE to test if a string does not match a pattern.
This is equivalent to using
the NOT operator on the entire LIKE expression.
If either the expression or the pattern is NULL, the result
is NULL.
LIKE performs case-insensitive substring matches if the
collation for the
expression and pattern is case-insensitive. For
case-sensitive matches, declare either argument
to use a binary collation using COLLATE, or coerce either of
them to a BINARY
string using CAST. Use SHOW COLLATION to get a list of
available collations. Collations ending in _bin are
case-sensitive.
Numeric arguments are coerced to binary strings.
The _ wildcard matches a single character, not byte. It will
only match a multi-byte character
if it is valid in the expression's character set. For
example, _ will match _utf8"€", but it
will not match _latin1"€" because the Euro sign is not a
valid latin1 character. If necessary,
use CONVERT to use the expression in a different character
set.
If you need to match the characters _ or %, you must escape
them. By default,
you can prefix the wildcard characters the backslash
character \ to escape them.
The backslash is used both to encode special characters like
newlines when a string is
parsed as well as to escape wildcards in a pattern after
parsing. Thus, to match an
actual backslash, you sometimes need to double-escape it as
"\\\\".
To avoid difficulties with the backslash character, you can
change the wildcard escape
character using ESCAPE in a LIKE expression. The argument to
ESCAPE
must be a single-character string.
Examples
--------
Select the days that begin with "T":
CREATE TABLE t1 (d VARCHAR(16));
INSERT INTO t1 VALUES ("Monday"), ("Tuesday"),
("Wednesday"), ("Thursday"), ("Friday"),
("Saturday"), ("Sunday");
SELECT * FROM t1 WHERE d LIKE "T%";
SELECT * FROM t1 WHERE d LIKE "T%";
+----------+
| d |
+----------+
| Tuesday |
| Thursday |
+----------+
Select the days that contain the substring "es":
SELECT * FROM t1 WHERE d LIKE "%es%";
SELECT * FROM t1 WHERE d LIKE "%es%";
+-----------+
| d |
+-----------+
| Tuesday |
| Wednesday |
+-----------+
Select the six-character day names:
SELECT * FROM t1 WHERE d like "___day";
SELECT * FROM t1 WHERE d like "___day";
+---------+
| d |
+---------+
| Monday |
| Friday |
| Sunday |
+---------+
With the default collations, LIKE is case-insensitive:
SELECT * FROM t1 where d like "t%";
SELECT * FROM t1 where d like "t%";
+----------+
| d |
+----------+
| Tuesday |
| Thursday |
+----------+
Use COLLATE to specify a binary collation, forcing
case-sensitive matches:
SELECT * FROM t1 WHERE d like "t%" COLLATE latin1_bin;
SELECT * FROM t1 WHERE d like "t%" COLLATE latin1_bin;
Empty set (0.00 sec)
You can include functions and operators in the expression to
match. Select dates
based on their day name:
CREATE TABLE t2 (d DATETIME);
INSERT INTO t2 VALUES
("2007-01-30 21:31:07"),
("1983-10-15 06:42:51"),
("2011-04-21 12:34:56"),
("2011-10-30 06:31:41"),
("2011-01-30 14:03:25"),
("2004-10-07 11:19:34");
SELECT * FROM t2 WHERE DAYNAME(d) LIKE "T%";
SELECT * FROM t2 WHERE DAYNAME(d) LIKE "T%";
+------------------+
| d |
+------------------+
| 2007-01-30 21:31 |
| 2011-04-21 12:34 |
| 2004-10-07 11:19 |
+------------------+
3 rows in set, 7 warnings (0.00 sec)
Optimizing LIKE
MariaDB can use indexes for LIKE on string columns in the
case where the LIKE doesn't start with % or _.
Starting from MariaDB 10.0, one can set the
optimizer_use_condition_selectivity variable to 5. If this
is done, then the optimizer will read
optimizer_selectivity_sampling_limit rows to calculate the
selectivity of the LIKE expression before starting to
calculate the query plan. This can help speed up some LIKE
queries by providing the optimizer with more information
about your data.
URL: https://mariadb.com/kb/en/like/https://mariadb.com/kb/en/like/ a ! % LOCATESyntax
------
LOCATE(substr,str), LOCATE(substr,str,pos)
Description
-----------
The first syntax returns the position of the first
occurrence of
substring substr in string str. The second syntax returns
the position
of the first occurrence of substring substr in string str,
starting at
position pos. Returns 0 if substr is not in str.
LOCATE() performs a case-insensitive search.
If any argument is NULL, returns NULL.
INSTR() is a synonym of LOCATE() without the third argument.
Examples
--------
SELECT LOCATE('bar', 'foobarbar');
+----------------------------+
| LOCATE('bar', 'foobarbar') |
+----------------------------+
| 4 |
+----------------------------+
SELECT LOCATE('My', 'Maria');
+-----------------------+
| LOCATE('My', 'Maria') |
+-----------------------+
| 0 |
+-----------------------+
SELECT LOCATE('bar', 'foobarbar', 5);
+-------------------------------+
| LOCATE('bar', 'foobarbar', 5) |
+-------------------------------+
| 7 |
+-------------------------------+
URL: https://mariadb.com/kb/en/locate/https://mariadb.com/kb/en/locate/ �I ����n �) b � % LOWERSyntax
------
LOWER(str)
Description
-----------
Returns the string str with all characters changed to
lowercase
according to the current character set mapping. The default
is latin1
(cp1252 West European).
Examples
--------
SELECT LOWER('QUADRATICALLY');
+------------------------+
| LOWER('QUADRATICALLY') |
+------------------------+
| quadratically |
+------------------------+
LOWER() (and UPPER()) are ineffective when applied to binary
strings (BINARY, VARBINARY, BLOB).
To perform lettercase conversion, CONVERT the string to a
non-binary string:
SET @str = BINARY 'North Carolina';
SELECT LOWER(@str), LOWER(CONVERT(@str USING latin1));
+----------------+-----------------------------------+
| LOWER(@str) | LOWER(CONVERT(@str USING latin1)) |
+----------------+-----------------------------------+
| North Carolina | north carolina |
+----------------+-----------------------------------+
URL: https://mariadb.com/kb/en/lower/https://mariadb.com/kb/en/lower/ c o % LPADSyntax
------
LPAD(str, len [,padstr])
Description
-----------
Returns the string str, left-padded with the string padstr
to a length
of len characters. If str is longer than len, the return
value is
shortened to len characters. If padstr is omitted, the LPAD
function pads spaces.
Prior to MariaDB 10.3.1, the padstr parameter was mandatory.
Returns NULL if given a NULL argument. If the result is
empty (zero length), returns either an empty string or, from
MariaDB 10.3.6 with SQL_MODE=Oracle, NULL.
The Oracle mode version of the function can be accessed
outside of Oracle mode by using LPAD_ORACLE as the function
name.
Examples
--------
SELECT LPAD('hello',10,'.');
+----------------------+
| LPAD('hello',10,'.') |
+----------------------+
| .....hello |
+----------------------+
SELECT LPAD('hello',2,'.');
+---------------------+
| LPAD('hello',2,'.') |
+---------------------+
| he |
+---------------------+
From MariaDB 10.3.1, with the pad string defaulting to
space.
SELECT LPAD('hello',10);
+------------------+
| LPAD('hello',10) |
+------------------+
| hello |
+------------------+
Oracle mode version from MariaDB 10.3.6:
SELECT LPAD('',0),LPAD_ORACLE('',0);
+------------+-------------------+
| LPAD('',0) | LPAD_ORACLE('',0) |
+------------+-------------------+
| | NULL |
+------------+-------------------+
URL: https://mariadb.com/kb/en/lpad/https://mariadb.com/kb/en/lpad/ d W % LTRIMSyntax
------
LTRIM(str)
Description
-----------
Returns the string str with leading space characters
removed.
Returns NULL if given a NULL argument. If the result is
empty, returns either an empty string, or, from MariaDB
10.3.6 with SQL_MODE=Oracle, NULL.
The Oracle mode version of the function can be accessed
outside of Oracle mode by using LTRIM_ORACLE as the function
name.
Examples
--------
SELECT QUOTE(LTRIM(' MariaDB '));
+-------------------------------+
| QUOTE(LTRIM(' MariaDB ')) |
+-------------------------------+
| 'MariaDB ' |
+-------------------------------+
Oracle mode version from MariaDB 10.3.6:
SELECT LTRIM(''),LTRIM_ORACLE('');
+-----------+------------------+
| LTRIM('') | LTRIM_ORACLE('') |
+-----------+------------------+
| | NULL |
+-----------+------------------+
URL: https://mariadb.com/kb/en/ltrim/https://mariadb.com/kb/en/ltrim/ e �# % MAKE_SETSyntax
------
MAKE_SET(bits,str1,str2,...)
Description
-----------
Returns a set value (a string containing substrings
separated by ","
characters) consisting of the strings that have the
corresponding bit
in bits set. str1 corresponds to bit 0, str2 to bit 1, and
so on. NULL
values in str1, str2, ... are not appended to the result.
Examples
--------
SELECT MAKE_SET(1,'a','b','c');
+-------------------------+
| MAKE_SET(1,'a','b','c') |
+-------------------------+
| a |
+-------------------------+
SELECT MAKE_SET(1 | 4,'hello','nice','world');
+----------------------------------------+
| MAKE_SET(1 | 4,'hello','nice','world') |
+----------------------------------------+
| hello,world |
+----------------------------------------+
SELECT MAKE_SET(1 | 4,'hello','nice',NULL,'world');
+---------------------------------------------+
| MAKE_SET(1 | 4,'hello','nice',NULL,'world') |
+---------------------------------------------+
| hello |
+---------------------------------------------+
SELECT QUOTE(MAKE_SET(0,'a','b','c'));
+--------------------------------+
| QUOTE(MAKE_SET(0,'a','b','c')) |
+--------------------------------+
| '' |
+--------------------------------+
URL: https://mariadb.com/kb/en/make_set/https://mariadb.com/kb/en/make_set/ f
0( % MATCH AGAINSTSyntax
------
MATCH (col1,col2,...) AGAINST (expr [search_modifier])
Description
-----------
A special construct used to perform a fulltext search on a
fulltext index.
See Fulltext Index Overview for a full description, and
Full-text Indexes for more articles on the topic.
Examples
--------
CREATE TABLE ft_myisam(copy TEXT,FULLTEXT(copy))
ENGINE=MyISAM;
INSERT INTO ft_myisam(copy) VALUES ('Once upon a time'),
('There was a wicked witch'),
('Who ate everybody up');
SELECT * FROM ft_myisam WHERE MATCH(copy)
AGAINST('wicked');
+--------------------------+
| copy |
+--------------------------+
| There was a wicked witch |
+--------------------------+
SELECT id, body, MATCH (title,body) AGAINST
('Security implications of running MySQL as root'
IN NATURAL LANGUAGE MODE) AS score
FROM articles WHERE MATCH (title,body) AGAINST
('Security implications of running MySQL as root'
IN NATURAL LANGUAGE MODE);
+----+-------------------------------------+-----------------+
| id | body | score |
+----+-------------------------------------+-----------------+
| 4 | 1. Never run mysqld as root. 2. ... | 1.5219271183014
|
| 6 | When configured properly, MySQL ... | 1.3114095926285
|
+----+-------------------------------------+-----------------+
URL: https://mariadb.com/kb/en/match-against/https://mariadb.com/kb/en/match-against/ Ls2
� �� ��؇ �� n �' % REGEXP_INSTRREGEXP_INSTR was introduced in MariaDB 10.0.5.
Syntax
------
REGEXP_INSTR(subject, pattern)
Returns the position of the first occurrence of the regular
expression pattern in the string subject, or 0 if pattern
was not found.
The positions start with 1 and are measured in characters
(i.e. not in bytes), which is important for multi-byte
character sets. You can cast a multi-byte character set to
BINARY to get offsets in bytes.
The function follows the case sensitivity rules of the
effective collation. Matching is performed case
insensitively for case insensitive collations, and case
sensitively for case sensitive collations and for binary
data.
The collation case sensitivity can be overwritten using the
(?i) and (?-i) PCRE flags.
MariaDB 10.0.5 switched to the PCRE regular expression
library for enhanced regular expression performance, and
REGEXP_INSTR was introduced as part of this enhancement.
Examples
--------
SELECT REGEXP_INSTR('abc','b');
-> 2
SELECT REGEXP_INSTR('abc','x');
-> 0
SELECT REGEXP_INSTR('BJÖRN','N');
-> 5
Casting a multi-byte character set as BINARY to get offsets
in bytes:
SELECT REGEXP_INSTR(BINARY 'BJÖRN','N') AS
cast_utf8_to_binary;
-> 6
Case sensitivity:
SELECT REGEXP_INSTR('ABC','b');
-> 2
SELECT REGEXP_INSTR('ABC' COLLATE utf8_bin,'b');
-> 0
SELECT REGEXP_INSTR(BINARY'ABC','b');
-> 0
SELECT REGEXP_INSTR('ABC','(?-i)b');
-> 0
SELECT REGEXP_INSTR('ABC' COLLATE utf8_bin,'(?i)b');
-> 2
URL: https://mariadb.com/kb/en/regexp_instr/https://mariadb.com/kb/en/regexp_instr/ o �) % REGEXP_REPLACEREGEXP_REPLACE was introduced in MariaDB 10.0.5.
Syntax
------
REGEXP_REPLACE(subject, pattern, replace)
Description
-----------
REGEXP_REPLACE returns the string subject with all
occurrences of the regular expression pattern replaced by
the string replace. If no occurrences are found, then
subject is returned as is.
The replace string can have backreferences to the
subexpressions in the form \N, where N is a number from 1
to 9.
The function follows the case sensitivity rules of the
effective collation. Matching is performed case
insensitively for case insensitive collations, and case
sensitively for case sensitive collations and for binary
data.
The collation case sensitivity can be overwritten using the
(?i) and (?-i) PCRE flags.
MariaDB 10.0.5 switched to the PCRE regular expression
library for enhanced regular expression performance, and
REGEXP_REPLACE was introduced as part of this enhancement.
MariaDB 10.0.11 introduced the default_regex_flags variable
to address the remaining compatibilities between PCRE and
the old regex library.
Examples
--------
SELECT REGEXP_REPLACE('ab12cd','[0-9]','') AS
remove_digits;
-> abcd
SELECT REGEXP_REPLACE('titlebody', '',' ')
AS strip_html;
-> title body
Backreferences to the subexpressions in the form \N, where
N is a number from 1 to 9:
SELECT REGEXP_REPLACE('James Bond','^(.*)
(.*)$','\\2, \\1') AS reorder_name;
-> Bond, James
Case insensitive and case sensitive matches:
SELECT REGEXP_REPLACE('ABC','b','-') AS
case_insensitive;
-> A-C
SELECT REGEXP_REPLACE('ABC' COLLATE utf8_bin,'b','-')
AS case_sensitive;
-> ABC
SELECT REGEXP_REPLACE(BINARY 'ABC','b','-') AS
binary_data;
-> ABC
Overwriting the collation case sensitivity using the (?i)
and (?-i) PCRE flags.
SELECT REGEXP_REPLACE('ABC','(?-i)b','-') AS
force_case_sensitive;
-> ABC
SELECT REGEXP_REPLACE(BINARY 'ABC','(?i)b','-') AS
force_case_insensitive;
-> A-C
URL: https://mariadb.com/kb/en/regexp_replace/https://mariadb.com/kb/en/regexp_replace/ p
c( % REGEXP_SUBSTRREGEXP_SUBSTR was introduced in MariaDB 10.0.5.
Syntax
------
REGEXP_SUBSTR(subject,pattern)
Description
-----------
Returns the part of the string subject that matches the
regular expression pattern, or an empty string if pattern
was not found.
The function follows the case sensitivity rules of the
effective collation. Matching is performed case
insensitively for case insensitive collations, and case
sensitively for case sensitive collations and for binary
data.
The collation case sensitivity can be overwritten using the
(?i) and (?-i) PCRE flags.
MariaDB 10.0.5 switched to the PCRE regular expression
library for enhanced regular expression performance, and
REGEXP_SUBSTR was introduced as part of this enhancement.
MariaDB 10.0.11 introduced the default_regex_flags variable
to address the remaining compatibilities between PCRE and
the old regex library.
Examples
--------
SELECT REGEXP_SUBSTR('ab12cd','[0-9]+');
-> 12
SELECT REGEXP_SUBSTR(
'See https://mariadb.org/en/foundation/ for details',
'https?://[^/]*');
-> https://mariadb.org
SELECT REGEXP_SUBSTR('ABC','b');
-> B
SELECT REGEXP_SUBSTR('ABC' COLLATE utf8_bin,'b');
->
SELECT REGEXP_SUBSTR(BINARY'ABC','b');
->
SELECT REGEXP_SUBSTR('ABC','(?i)b');
-> B
SELECT REGEXP_SUBSTR('ABC' COLLATE utf8_bin,'(?+i)b');
-> B
URL: https://mariadb.com/kb/en/regexp_substr/https://mariadb.com/kb/en/regexp_substr/ P�F
:u� �B u � % RPADSyntax
------
RPAD(str, len [, padstr])
Description
-----------
Returns the string str, right-padded with the string padstr
to a
length of len characters. If str is longer than len, the
return value
is shortened to len characters. If padstr is omitted, the
RPAD function pads spaces.
Prior to MariaDB 10.3.1, the padstr parameter was mandatory.
Returns NULL if given a NULL argument. If the result is
empty (a length of zero), returns either an empty string,
or, from MariaDB 10.3.6 with SQL_MODE=Oracle, NULL.
The Oracle mode version of the function can be accessed
outside of Oracle mode by using RPAD_ORACLE as the function
name.
Examples
--------
SELECT RPAD('hello',10,'.');
+----------------------+
| RPAD('hello',10,'.') |
+----------------------+
| hello..... |
+----------------------+
SELECT RPAD('hello',2,'.');
+---------------------+
| RPAD('hello',2,'.') |
+---------------------+
| he |
+---------------------+
From MariaDB 10.3.1, with the pad string defaulting to
space.
SELECT RPAD('hello',30);
+--------------------------------+
| RPAD('hello',30) |
+--------------------------------+
| hello |
+--------------------------------+
Oracle mode version from MariaDB 10.3.6:
SELECT RPAD('',0),RPAD_ORACLE('',0);
+------------+-------------------+
| RPAD('',0) | RPAD_ORACLE('',0) |
+------------+-------------------+
| | NULL |
+------------+-------------------+
URL: https://mariadb.com/kb/en/rpad/https://mariadb.com/kb/en/rpad/ v O % RTRIMSyntax
------
RTRIM(str)
Description
-----------
Returns the string str with trailing space characters
removed.
Returns NULL if given a NULL argument. If the result is
empty, returns either an empty string, or, from MariaDB
10.3.6 with SQL_MODE=Oracle, NULL.
The Oracle mode version of the function can be accessed
outside of Oracle mode by using RTRIM_ORACLE as the function
name.
Examples
--------
SELECT QUOTE(RTRIM('MariaDB '));
+-----------------------------+
| QUOTE(RTRIM('MariaDB ')) |
+-----------------------------+
| 'MariaDB' |
+-----------------------------+
Oracle mode version from MariaDB 10.3.6:
SELECT RTRIM(''),RTRIM_ORACLE('');
+-----------+------------------+
| RTRIM('') | RTRIM_ORACLE('') |
+-----------+------------------+
| | NULL |
+-----------+------------------+
URL: https://mariadb.com/kb/en/rtrim/https://mariadb.com/kb/en/rtrim/ w �" % SOUNDEXSyntax
------
SOUNDEX(str)
Description
-----------
Returns a soundex string from str. Two strings that sound
almost the
same should have identical soundex strings. A standard
soundex string is four
characters long, but the SOUNDEX() function returns an
arbitrarily long
string. You can use SUBSTRING() on the result to get a
standard soundex
string. All non-alphabetic characters in str are ignored.
All
international alphabetic characters outside the A-Z range
are treated as
vowels.
Important: When using SOUNDEX(), you should be aware of the
following limitations:
This function, as currently implemented, is intended to work
well with
strings that are in the English language only. Strings in
other languages may
not produce reliable results.
Examples
--------
SOUNDEX('Hello');
+------------------+
| SOUNDEX('Hello') |
+------------------+
| H400 |
+------------------+
SELECT SOUNDEX('MariaDB');
+--------------------+
| SOUNDEX('MariaDB') |
+--------------------+
| M631 |
+--------------------+
SELECT SOUNDEX('Knowledgebase');
+--------------------------+
| SOUNDEX('Knowledgebase') |
+--------------------------+
| K543212 |
+--------------------------+
SELECT givenname, surname FROM users WHERE
SOUNDEX(givenname) = SOUNDEX("robert");
+-----------+---------+
| givenname | surname |
+-----------+---------+
| Roberto | Castro |
+-----------+---------+
URL: https://mariadb.com/kb/en/soundex/https://mariadb.com/kb/en/soundex/ | G $ % SUBSTRINGSyntax
------
SUBSTRING(str,pos),
SUBSTRING(str FROM pos),
SUBSTRING(str,pos,len),
SUBSTRING(str FROM pos FOR len)
SUBSTR(str,pos),
SUBSTR(str FROM pos),
SUBSTR(str,pos,len),
SUBSTR(str FROM pos FOR len)
Description
-----------
The forms without a len argument return a substring from
string str starting at position pos.
The forms with a len argument return a substring len
characters long from string str, starting at position pos.
The forms that use FROM are standard SQL syntax.
It is also possible to use a negative value for pos. In this
case, the beginning of the substring is pos characters from
the end of the string, rather than the beginning. A negative
value may be used for pos in any of the forms of this
function.
By default, the position of the first character in the
string from which the substring is to be extracted is
reckoned as 1. For Oracle-compatibility, from MariaDB
10.3.3, when sql_mode is set to 'oracle', position zero is
treated as position 1 (although the first character is still
reckoned as 1).
If any argument is NULL, returns NULL.
Examples
--------
SELECT SUBSTRING('Knowledgebase',5);
+------------------------------+
| SUBSTRING('Knowledgebase',5) |
+------------------------------+
| ledgebase |
+------------------------------+
SELECT SUBSTRING('MariaDB' FROM 6);
+-----------------------------+
| SUBSTRING('MariaDB' FROM 6) |
+-----------------------------+
| DB |
+-----------------------------+
SELECT SUBSTRING('Knowledgebase',3,7);
+--------------------------------+
| SUBSTRING('Knowledgebase',3,7) |
+--------------------------------+
| owledge |
+--------------------------------+
SELECT SUBSTRING('Knowledgebase', -4);
+--------------------------------+
| SUBSTRING('Knowledgebase', -4) |
+--------------------------------+
| base |
+--------------------------------+
SELECT SUBSTRING('Knowledgebase', -8, 4);
+-----------------------------------+
| SUBSTRING('Knowledgebase', -8, 4) |
+-----------------------------------+
| edge |
+-----------------------------------+
SELECT SUBSTRING('Knowledgebase' FROM -8 FOR 4);
+------------------------------------------+
| SUBSTRING('Knowledgebase' FROM -8 FOR 4) |
+------------------------------------------+
| edge |
+------------------------------------------+
Oracle mode from MariaDB 10.3.3:
SELECT SUBSTR('abc',0,3);
+-------------------+
| SUBSTR('abc',0,3) |
+-------------------+
| |
+-------------------+
SELECT SUBSTR('abc',1,2);
+-------------------+
| SUBSTR('abc',1,2) |
+-------------------+
| ab |
+-------------------+
SET sql_mode='oracle';
SELECT SUBSTR('abc',0,3);
+-------------------+
| SUBSTR('abc',0,3) |
+-------------------+
| abc |
+-------------------+
SELECT SUBSTR('abc',1,2);
+-------------------+
| SUBSTR('abc',1,2) |
+-------------------+
| ab |
+-------------------+
URL: https://mariadb.com/kb/en/substring/https://mariadb.com/kb/en/substring/ (� ` ��� ���P1 � } :* % SUBSTRING_INDEXSyntax
------
SUBSTRING_INDEX(str,delim,count)
Description
-----------
Returns the substring from string str before count
occurrences of the
delimiter delim. If count is positive, everything to the
left
of the final delimiter (counting from the left) is returned.
If count
is negative, everything to the right of the final delimiter
(counting from the
right) is returned. SUBSTRING_INDEX() performs a
case-sensitive match when
searching for delim.
If any argument is NULL, returns NULL.
Examples
--------
SELECT SUBSTRING_INDEX('www.mariadb.org', '.', 2);
+--------------------------------------------+
| SUBSTRING_INDEX('www.mariadb.org', '.', 2) |
+--------------------------------------------+
| www.mariadb |
+--------------------------------------------+
SELECT SUBSTRING_INDEX('www.mariadb.org', '.', -2);
+---------------------------------------------+
| SUBSTRING_INDEX('www.mariadb.org', '.', -2) |
+---------------------------------------------+
| mariadb.org |
+---------------------------------------------+
URL: https://mariadb.com/kb/en/substring_index/https://mariadb.com/kb/en/substring_index/ ~ �$ % TO_BASE64The TO_BASE64() function was introduced in MariaDB 10.0.5.
Syntax
------
TO_BASE64(str)
Description
-----------
Converts the string argument str to its base-64 encoded
form, returning the result as a character string in the
connection character set and collation.
The argument str will be converted to string first if it is
not a string. A NULL argument will return a NULL result.
The reverse function, FROM_BASE64(), decodes an encoded
base-64 string.
There are a numerous different methods to base-64 encode a
string. The following are used by MariaDB and MySQL:
Alphabet value 64 is encoded as '+'.
Alphabet value 63 is encoded as '/'.
Encoding output is made up of groups of four printable
characters, with each three bytes of data encoded using four
characters. If the final group is not complete, it is padded
with '=' characters to make up a length of four.
To divide long output, a newline is added after every 76
characters.
Decoding will recognize and ignore newlines, carriage
returns, tabs, and spaces.
Examples
--------
SELECT TO_BASE64('Maria');
+--------------------+
| TO_BASE64('Maria') |
+--------------------+
| TWFyaWE= |
+--------------------+
URL: https://mariadb.com/kb/en/to_base64/https://mariadb.com/kb/en/to_base64/ � % TRIMSyntax
------
TRIM([{BOTH | LEADING | TRAILING} [remstr] FROM] str),
TRIM([remstr FROM] str)
Description
-----------
Returns the string str with all remstr prefixes or suffixes
removed. If none of the specifiers BOTH, LEADING, or
TRAILING is given, BOTH is assumed. remstr is optional and,
if not specified, spaces are removed.
Returns NULL if given a NULL argument. If the result is
empty, returns either an empty string, or, from MariaDB
10.3.6 with SQL_MODE=Oracle, NULL.
The Oracle mode version of the function can be accessed
outside of Oracle mode by using TRIM_ORACLE as the function
name.
Examples
--------
SELECT TRIM(' bar ')\G
*************************** 1. row
***************************
TRIM(' bar '): bar
SELECT TRIM(LEADING 'x' FROM 'xxxbarxxx')\G
*************************** 1. row
***************************
TRIM(LEADING 'x' FROM 'xxxbarxxx'): barxxx
SELECT TRIM(BOTH 'x' FROM 'xxxbarxxx')\G
*************************** 1. row
***************************
TRIM(BOTH 'x' FROM 'xxxbarxxx'): bar
SELECT TRIM(TRAILING 'xyz' FROM 'barxxyz')\G
*************************** 1. row
***************************
TRIM(TRAILING 'xyz' FROM 'barxxyz'): barx
Oracle mode version from MariaDB 10.3.6:
SELECT TRIM(''),TRIM_ORACLE('');
+----------+-----------------+
| TRIM('') | TRIM_ORACLE('') |
+----------+-----------------+
| | NULL |
+----------+-----------------+
URL: https://mariadb.com/kb/en/trim/https://mariadb.com/kb/en/trim/ � 1 % UNHEXSyntax
------
UNHEX(str)
Description
-----------
Performs the inverse operation of HEX(str). That is, it
interprets
each pair of hexadecimal digits in the argument as a number
and
converts it to the character represented by the number. The
resulting
characters are returned as a binary string.
If str is NULL, UNHEX() returns NULL.
Examples
--------
SELECT HEX('MariaDB');
+----------------+
| HEX('MariaDB') |
+----------------+
| 4D617269614442 |
+----------------+
SELECT UNHEX('4D617269614442');
+-------------------------+
| UNHEX('4D617269614442') |
+-------------------------+
| MariaDB |
+-------------------------+
SELECT 0x4D617269614442;
+------------------+
| 0x4D617269614442 |
+------------------+
| MariaDB |
+------------------+
SELECT UNHEX(HEX('string'));
+----------------------+
| UNHEX(HEX('string')) |
+----------------------+
| string |
+----------------------+
SELECT HEX(UNHEX('1267'));
+--------------------+
| HEX(UNHEX('1267')) |
+--------------------+
| 1267 |
+--------------------+
URL: https://mariadb.com/kb/en/unhex/https://mariadb.com/kb/en/unhex/ hd� �� ���� �� � �$ % UPDATEXMLSyntax
------
UpdateXML(xml_target, xpath_expr, new_xml)
Description
-----------
This function replaces a single portion of a given fragment
of XML markup
xml_target with a new XML fragment new_xml, and then returns
the
changed XML. The portion of xml_target that is replaced
matches an XPath
expression xpath_expr supplied by the user. If no expression
matching
xpath_expr is found, or if multiple matches are found, the
function returns
the original xml_target XML fragment. All three arguments
should be
strings.
Examples
--------
SELECT
UpdateXML('ccc', '/a', 'fff') AS val1,
UpdateXML('ccc', '/b', 'fff') AS val2,
UpdateXML('ccc', '//b', 'fff') AS val3,
UpdateXML('ccc', '/a/d', 'fff') AS val4,
UpdateXML('ccc', '/a/d', 'fff') AS val5
\G
*************************** 1. row
***************************
val1: fff
val2: ccc
val3: fff
val4: cccfff
val5: ccc
1 row in set (0.00 sec)
URL: https://mariadb.com/kb/en/updatexml/https://mariadb.com/kb/en/updatexml/ �
�
( % WEIGHT_STRINGThe WEIGHT_STRING function was introduced in MariaDB 10.0.5.
Syntax
------
WEIGHT_STRING(str [AS {CHAR|BINARY}(N)] [LEVEL levels]
[flags])
levels: N [ASC|DESC|REVERSE] [, N [ASC|DESC|REVERSE]] ...
Description
-----------
Returns a binary string representing the string's sorting
and comparison value. A string with a lower result means
that for sorting purposes the string appears before a string
with a higher result.
WEIGHT_STRING() is particularly useful when adding new
collations, for testing purposes.
If str is a non-binary string (CHAR, VARCHAR or TEXT),
WEIGHT_STRING returns the string's collation weight. If str
is a binary string (BINARY, VARBINARY or BLOB), the return
value is simply the input value, since the weight for each
byte in a binary string is the byte value.
WEIGHT_STRING() returns NULL if given a NULL input.
The optional AS clause permits casting the input string to a
binary or non-binary string, as well as to a particular
length.
AS BINARY(N) measures the length in bytes rather than
characters, and right pads with 0x00 bytes to the desired
length.
AS CHAR(N) measures the length in characters, and right pads
with spaces to the desired length.
N has a minimum value of 1, and if it is less than the
length of the input string, the string is truncated without
warning.
The optional LEVEL clause specifies that the return value
should contain weights for specific collation levels. The
levels specifier can either be a single integer, a
comma-separated list of integers, or a range of integers
separated by a dash (whitespace is ignored). Integers can
range from 1 to a maximum of 6, dependent on the collation,
and need to be listed in ascending order.
If the LEVEL clause is no provided, a default of 1 to the
maximum for the collation is assumed.
If the LEVEL is specified without using a range, an optional
modifier is permitted.
ASC, the default, returns the weights without any
modification.
DESC returns bitwise-inverted weights.
REVERSE returns the weights in reverse order.
Examples
--------
The examples below use the HEX() function to represent
non-printable results in hexadecimal format.
SELECT HEX(WEIGHT_STRING('x'));
+-------------------------+
| HEX(WEIGHT_STRING('x')) |
+-------------------------+
| 0058 |
+-------------------------+
SELECT HEX(WEIGHT_STRING('x' AS BINARY(4)));
+--------------------------------------+
| HEX(WEIGHT_STRING('x' AS BINARY(4))) |
+--------------------------------------+
| 78000000 |
+--------------------------------------+
SELECT HEX(WEIGHT_STRING('x' AS CHAR(4)));
+------------------------------------+
| HEX(WEIGHT_STRING('x' AS CHAR(4))) |
+------------------------------------+
| 0058002000200020 |
+------------------------------------+
SELECT HEX(WEIGHT_STRING(0xaa22ee LEVEL 1));
+--------------------------------------+
| HEX(WEIGHT_STRING(0xaa22ee LEVEL 1)) |
+--------------------------------------+
| AA22EE |
+--------------------------------------+
SELECT HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 DESC));
+-------------------------------------------+
| HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 DESC)) |
+-------------------------------------------+
| 55DD11 |
+-------------------------------------------+
SELECT HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 REVERSE));
+----------------------------------------------+
| HEX(WEIGHT_STRING(0xaa22ee LEVEL 1 REVERSE)) |
+----------------------------------------------+
| EE22AA |
+----------------------------------------------+
URL: https://mariadb.com/kb/en/weight_string/https://mariadb.com/kb/en/weight_string/ � � ) ' ALTER DATABASEModifies a database, changing its overall characteristics.
Syntax
------
ALTER {DATABASE | SCHEMA} [db_name]
alter_specification ...
ALTER {DATABASE | SCHEMA} db_name
UPGRADE DATA DIRECTORY NAME
alter_specification:
[DEFAULT] CHARACTER SET [=] charset_name
| [DEFAULT] COLLATE [=] collation_name
Description
-----------
ALTER DATABASE enables you to change the overall
characteristics of a
database. These characteristics are stored in the db.opt
file in the
database directory. To use ALTER DATABASE, you need the
ALTER
privilege on the database. ALTER SCHEMA is a synonym for
ALTER
DATABASE.
The CHARACTER SET clause changes the default database
character set.
The COLLATE clause changes the default database collation.
See Character Sets and Collations for more.
You can see what character sets and collations are available
using,
respectively, the SHOW CHARACTER SET and SHOW COLLATION
statements.
Changing the default character set/collation of a database
does not change the character set/collation of any stored
procedures or stored functions that were previously created,
and relied on the defaults. These need to be dropped and
recreated in order to apply the character set/collation
changes.
The database name can be omitted from the first syntax, in
which case
the statement applies to the default database.
The syntax that includes the UPGRADE DATA DIRECTORY NAME
clause was
added in MySQL 5.1.23. It updates the name of the directory
associated
with the database to use the encoding implemented in MySQL
5.1 for
mapping database names to database directory names (see
Identifier to File Name Mapping). This
clause is for use under these conditions:
It is intended when upgrading MySQL to 5.1 or later from
older versions.
It is intended to update a database directory name to the
current encoding format if the name contains special
characters that need encoding.
The statement is used by mysqlcheck (as invoked by
mysql_upgrade).
For example,if a database in MySQL 5.0 has a name of a-b-c,
the name
contains instance of the `-' character. In 5.0, the
database directory
is also named a-b-c, which is not necessarily safe for all
file
systems. In MySQL 5.1 and up, the same database name is
encoded as
a@002db@002dc to produce a file system-neutral directory
name.
When a MySQL installation is upgraded to MySQL 5.1 or later
from an
older version,the server displays a name such as a-b-c
(which is in
the old format) as #mysql50#a-b-c, and you must refer to the
name
using the #mysql50# prefix. Use UPGRADE DATA DIRECTORY NAME
in this
case to explicitly tell the server to re-encode the database
directory
name to the current encoding format:
ALTER DATABASE `#mysql50#a-b-c` UPGRADE DATA DIRECTORY NAME;
After executing this statement, you can refer to the
database as a-b-c
without the special #mysql50# prefix.
Examples
--------
ALTER DATABASE test CHARACTER SET = 'utf8' COLLATE =
'utf8_bin';
URL: https://mariadb.com/kb/en/alter-database/https://mariadb.com/kb/en/alter-database/ 3� 1 ��@� �X � �& ' ALTER EVENTModifies one or more characteristics of an existing event.
Syntax
------
ALTER
[DEFINER = { user | CURRENT_USER }]
EVENT event_name
[ON SCHEDULE schedule]
[ON COMPLETION [NOT] PRESERVE]
[RENAME TO new_event_name]
[ENABLE | DISABLE | DISABLE ON SLAVE]
[COMMENT 'comment']
[DO sql_statement]
Description
-----------
The ALTER EVENT statement is used to change one or more of
the
characteristics of an existing event without the need to
drop and recreate it.
The syntax for each of the DEFINER, ON SCHEDULE, ON
COMPLETION,
COMMENT, ENABLE / DISABLE, and DO clauses is exactly the
same as when used with CREATE EVENT.
This statement requires the EVENT privilege.
When a user executes a successful ALTER EVENT statement,
that user becomes
the definer for the affected event.
(In MySQL 5.1.11 and earlier, an event could be altered only
by its definer, or
by a user having the SUPER privilege.)
ALTER EVENT works only with an existing event:
ALTER EVENT no_such_event ON SCHEDULE EVERY '2:3'
DAY_HOUR;
ERROR 1539 (HY000): Unknown event 'no_such_event'
Examples
--------
ALTER EVENT myevent
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 2 HOUR
DO
UPDATE myschema.mytable SET mycol = mycol + 1;
URL: https://mariadb.com/kb/en/alter-event/https://mariadb.com/kb/en/alter-event/ � �) ' ALTER FUNCTIONSyntax
------
ALTER FUNCTION func_name [characteristic ...]
characteristic:
{ CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL
DATA }
| SQL SECURITY { DEFINER | INVOKER }
| COMMENT 'string'
Description
-----------
This statement can be used to change the characteristics of
a stored
function. More than one change may be specified in an ALTER
FUNCTION
statement. However, you cannot change the parameters or body
of a
stored function using this statement; to make such changes,
you must
drop and re-create the function using DROP FUNCTION and
CREATE FUNCTION.
You must have the ALTER ROUTINE privilege for the function.
(That
privilege is granted automatically to the function creator.)
If binary
logging is enabled, the ALTER FUNCTION statement might also
require
the SUPER privilege, as described in Binary Logging of
Stored Routines.
Example
ALTER FUNCTION hello SQL SECURITY INVOKER;
URL: https://mariadb.com/kb/en/alter-function/https://mariadb.com/kb/en/alter-function/ � �* ' ALTER PROCEDURESyntax
------
ALTER PROCEDURE proc_name [characteristic ...]
characteristic:
{ CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL
DATA }
| SQL SECURITY { DEFINER | INVOKER }
| COMMENT 'string'
Description
-----------
This statement can be used to change the characteristics of
a stored
procedure. More than one change may be specified in an ALTER
PROCEDURE
statement. However, you cannot change the parameters or body
of a
stored procedure using this statement. To make such changes,
you must
drop and re-create the procedure using either CREATE OR
REPLACE PROCEDURE (since MariaDB 10.1.3) or DROP PROCEDURE
and CREATE PROCEDURE (MariaDB 10.1.2 and before).
You must have the ALTER ROUTINE privilege for the procedure.
By default, that privilege is granted automatically to the
procedure creator. See Stored Routine Privileges.
Example
ALTER PROCEDURE simpleproc SQL SECURITY INVOKER;
URL: https://mariadb.com/kb/en/alter-procedure/https://mariadb.com/kb/en/alter-procedure/ �
% ' ALTER VIEWSyntax
------
ALTER
[ALGORITHM = {UNDEFINED | MERGE | TEMPTABLE}]
[DEFINER = { user | CURRENT_USER }]
[SQL SECURITY { DEFINER | INVOKER }]
VIEW view_name [(column_list)]
AS select_statement
[WITH [CASCADED | LOCAL] CHECK OPTION]
Description
-----------
This statement changes the definition of a view, which must
exist. The
syntax is similar to that for CREATE VIEW and the effect is
the same
as for CREATE OR REPLACE VIEW if the view exists. This
statement
requires the CREATE VIEW and DROP privileges for the view,
and some
privilege for each column referred to in the SELECT
statement. As of
MariaDB 5.1.23, ALTER VIEW is allowed only to the definer or
users with
the SUPER privilege.
Example
ALTER VIEW v AS SELECT a, a*3 AS a2 FROM t;
URL: https://mariadb.com/kb/en/alter-view/https://mariadb.com/kb/en/alter-view/ � �* ' CREATE DATABASESyntax
------
CREATE [OR REPLACE] {DATABASE | SCHEMA} [IF NOT EXISTS]
db_name
[create_specification] ...
create_specification:
[DEFAULT] CHARACTER SET [=] charset_name
| [DEFAULT] COLLATE [=] collation_name
Description
-----------
CREATE DATABASE creates a database with the given name. To
use this statement, you need the CREATE privilege for the
database. CREATE SCHEMA is a synonym for CREATE DATABASE.
For valid identifiers to use as database names, see
Identifier Names.
OR REPLACE
The OR REPLACE clause was added in MariaDB 10.1.3
If the optional OR REPLACE clause is used, it acts as a
shortcut for:
DROP DATABASE IF EXISTS db_name;
CREATE DATABASE db_name ...;
IF NOT EXISTS
When the IF NOT EXISTS clause is used, MariaDB will return a
warning instead of an error if the specified database
already exists.
Examples
--------
CREATE DATABASE db1;
Query OK, 1 row affected (0.18 sec)
CREATE DATABASE db1;
ERROR 1007 (HY000): Can't create database 'db1'; database
exists
CREATE OR REPLACE DATABASE db1;
Query OK, 2 rows affected (0.00 sec)
CREATE DATABASE IF NOT EXISTS db1;
Query OK, 1 row affected, 1 warning (0.01 sec)
SHOW WARNINGS;
+-------+------+----------------------------------------------+
| Level | Code | Message |
+-------+------+----------------------------------------------+
| Note | 1007 | Can't create database 'db1';
database exists |
+-------+------+----------------------------------------------+
Setting the character sets and collation. See Setting
Character Sets and Collations for more details.
CREATE DATABASE czech_slovak_names
CHARACTER SET = 'keybcs2'
COLLATE = 'keybcs2_bin';
URL: https://mariadb.com/kb/en/create-database/https://mariadb.com/kb/en/create-database/ ��>
]= : . @� �d � ") ' ALTER SEQUENCEALTER SEQUENCE was introduced in MariaDB 10.3.
Syntax
------
ALTER SEQUENCE [IF EXISTS] sequence_name
[ INCREMENT [ BY | = ] increment ]
[ MINVALUE [=] minvalue | NO MINVALUE | NOMINVALUE ]
[ MAXVALUE [=] maxvalue | NO MAXVALUE | NOMAXVALUE ]
[ START [ WITH | = ] start ] [ CACHE [=] cache ] [ [ NO ]
CYCLE ]
[ RESTART [[WITH | =] restart]
ALTER SEQUENCE allows one to change any values for a
SEQUENCE created with CREATE SEQUENCE.
The options for ALTER SEQUENCE can be given in any order.
Description
-----------
ALTER SEQUENCE changes the parameters of an existing
sequence generator. Any parameters not specifically set in
the ALTER SEQUENCE command retain their prior settings.
ALTER SEQUENCE requires the ALTER privilege.
Arguments to ALTER SEQUENCE
The following options may be used:
Option | Default value | Description |
INCREMENT | 1 | Increment to use for values. May be
negative. |
MINVALUE | 1 if INCREMENT > 0 and -9223372036854775807 if
INCREMENT < 0 | Minimum value for the sequence. |
MAXVALUE | 9223372036854775806 if INCREMENT > 0 and -1 if
INCREMENT < 0 | Max value for sequence. |
START | MINVALUE if INCREMENT > 0 and MAX_VALUE if
INCREMENT< 0 | First value that the sequence will generate.
|
CACHE | 1000 | Number of values that should be cached. 0 if
no CACHE. The underlying table will be updated first time a
new sequence number is generated and each time the cache
runs out. |
CYCLE | 0 (= NO CYCLE) | 1 if the sequence should start
again from MINVALUE# after it has run out of values. |
RESTART | START if restart value not is given | If RESTART
option is used, NEXT VALUE will return the restart value. |
The optional clause RESTART [ WITH restart ] sets the next
value for the sequence. This is equivalent to calling the
SETVAL() function with the is_used argument as 0. The
specified value will be returned by the next call of
nextval. Using RESTART with no restart value is
equivalent to supplying the start value that was recorded by
CREATE SEQUENCE or last set by ALTER SEQUENCE START WITH.
ALTER SEQUENCE will not allow you to change the sequence so
that it's inconsistent. For example:
CREATE SEQUENCE s1;
ALTER SEQUENCE s1 MINVALUE 10;
ERROR 4061 (HY000): Sequence 'test.t1' values are
conflicting
ALTER SEQUENCE s1 MINVALUE 10 RESTART 10;
ERROR 4061 (HY000): Sequence 'test.t1' values are
conflicting
ALTER SEQUENCE s1 MINVALUE 10 START 10 RESTART 10;
INSERT
To allow SEQUENCE objects to be backed up by old tools, like
mysqldump, one can use SELECT to read the current state of a
SEQUENCE object and use an INSERT to update the SEQUENCE
object. INSERT is only allowed if all fields are specified:
CREATE SEQUENCE s1;
INSERT INTO s1 VALUES(1000,10,2000,1005,1,1000,0,0);
SELECT * FROM s1;
+------------+-----------+-----------+-------+-----------+-------+-------+-------+
| next_value | min_value | max_value | start | increment |
cache | cycle | round |
+------------+-----------+-----------+-------+-----------+-------+-------+-------+
| 1000 | 10 | 2000 | 1005 | 1 | 1000 | 0 | 0 |
+------------+-----------+-----------+-------+-----------+-------+-------+-------+
SHOW CREATE SEQUENCE s1;
+-------+--------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+-------+--------------------------------------------------------------------------------------------------------------+
| s1 | CREATE SEQUENCE `s1` start with 1005 minvalue 10
maxvalue 2000 increment by 1 cache 1000 nocycle ENGINE=Aria
|
+-------+--------------------------------------------------------------------------------------------------------------+
Notes
ALTER SEQUENCE will instantly affect all future SEQUENCE
operations. This is in contrast to some other databases
where the changes requested by ALTER SEQUENCE will not be
seen until the sequence cache has run out.
ALTER SEQUENCE will take a full table lock of the sequence
object during
its (brief) operation. This ensures that ALTER SEQUENCE is
replicated
correctly. If you only want to set the next sequence value
to a
higher value than current, then you should use SETVAL()
instead, as this is not blocking.
If you want to change storage engine, sequence comment or
rename the sequence, you can use ALTER TABLE for this.
URL: https://mariadb.com/kb/en/alter-sequence/https://mariadb.com/kb/en/alter-sequence/ � �) ' CREATE PACKAGEOracle-style packages were introduced in MariaDB 10.3.5.
Syntax
------
CREATE
[ OR REPLACE]
[DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
PACKAGE [ IF NOT EXISTS ]
[ db_name . ] package_name
[ package_characteristic ... ]
{ AS | IS }
[ package_specification_element ... ]
END [ package_name ]
package_characteristic:
COMMENT 'string'
| SQL SECURITY { DEFINER | INVOKER }
package_specification_element:
FUNCTION_SYM package_specification_function ;
| PROCEDURE_SYM package_specification_procedure ;
package_specification_function:
func_name [ ( func_param [, func_param]... ) ]
RETURNS func_return_type
[ package_routine_characteristic... ]
package_specification_procedure:
proc_name [ ( proc_param [, proc_param]... ) ]
[ package_routine_characteristic... ]
func_return_type:
type
func_param:
param_name type
proc_param:
param_name { IN | OUT | INOUT | IN OUT } type
type:
Any valid MariaDB explicit or anchored data type
package_routine_characteristic:
COMMENT 'string'
| LANGUAGE SQL
| { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL
DATA }
| SQL SECURITY { DEFINER | INVOKER }
Description
-----------
The CREATE PACKAGE statement can be used when Oracle
SQL_MODE is set.
The CREATE PACKAGE creates the specification for a stored
package (a collection of logically related stored objects).
A stored package specification declares public routines
(procedures and functions) of the package, but does not
implement these routines.
A package whose specification was created by the CREATE
PACKAGE statement, should later be implemented using the
CREATE PACKAGE BODY statement.
Examples
--------
SET sql_mode=ORACLE;
DELIMITER $$
CREATE OR REPLACE PACKAGE employee_tools AS
FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2);
PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2));
PROCEDURE raiseSalaryStd(eid INT);
PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2));
END;
$$
DELIMITER ;
URL: https://mariadb.com/kb/en/create-package/https://mariadb.com/kb/en/create-package/ s gN�+^ Syntax
------
ALTER [ONLINE] [IGNORE] TABLE tbl_name
[WAIT n | NOWAIT]
alter_specification [, alter_specification] ...
alter_specification:
table_option ...
| ADD [COLUMN] [IF NOT EXISTS] col_name column_definition
[FIRST | AFTER col_name ]
| ADD [COLUMN] [IF NOT EXISTS] (col_name
column_definition,...)
| ADD {INDEX|KEY} [IF NOT EXISTS] [index_name]
[index_type] (index_col_name,...) [index_option] ...
| ADD [CONSTRAINT [symbol]] PRIMARY KEY
[index_type] (index_col_name,...) [index_option] ...
| ADD [CONSTRAINT [symbol]]
UNIQUE [INDEX|KEY] [index_name]
[index_type] (index_col_name,...) [index_option] ...
| ADD FULLTEXT [INDEX|KEY] [index_name]
(index_col_name,...) [index_option] ...
| ADD SPATIAL [INDEX|KEY] [index_name]
(index_col_name,...) [index_option] ...
| ADD [CONSTRAINT [symbol]]
FOREIGN KEY [IF NOT EXISTS] [index_name]
(index_col_name,...)
reference_definition
| ADD PERIOD FOR SYSTEM_TIME (start_column_name,
end_column_name)
| ALTER [COLUMN] col_name SET DEFAULT literal
| (expression)
| ALTER [COLUMN] col_name DROP DEFAULT
| CHANGE [COLUMN] [IF EXISTS] old_col_name new_col_name
column_definition
[FIRST|AFTER col_name]
| MODIFY [COLUMN] [IF EXISTS] col_name column_definition
[FIRST | AFTER col_name]
| DROP [COLUMN] [IF EXISTS] col_name [RESTRICT|CASCADE]
| DROP PRIMARY KEY
| DROP {INDEX|KEY} [IF EXISTS] index_name
| DROP FOREIGN KEY [IF EXISTS] fk_symbol
| DROP CONSTRAINT [IF EXISTS] constraint_name
| DISABLE KEYS
| ENABLE KEYS
| RENAME [TO] new_tbl_name
| ORDER BY col_name [, col_name] ...
| CONVERT TO CHARACTER SET charset_name [COLLATE
collation_name]
| [DEFAULT] CHARACTER SET [=] charset_name
| [DEFAULT] COLLATE [=] collation_name
| DISCARD TABLESPACE
| IMPORT TABLESPACE
| ALGORITHM [=] {DEFAULT|INPLACE|COPY|NOCOPY|INSTANT}
| LOCK [=] {DEFAULT|NONE|SHARED|EXCLUSIVE}
| FORCE
| partition_options
| ADD PARTITION (partition_definition)
| DROP PARTITION partition_names
| COALESCE PARTITION number
| REORGANIZE PARTITION [partition_names INTO
(partition_definitions)]
| ANALYZE PARTITION partition_names
| CHECK PARTITION partition_names
| OPTIMIZE PARTITION partition_names
| REBUILD PARTITION partition_names
| REPAIR PARTITION partition_names
| EXCHANGE PARTITION partition_name WITH TABLE tbl_name
| REMOVE PARTITIONING
| ADD SYSTEM VERSIONING
| DROP SYSTEM VERSIONING
index_col_name:
col_name [(length)] [ASC | DESC]
index_type:
USING {BTREE | HASH | RTREE}
index_option:
KEY_BLOCK_SIZE [=] value
| index_type
| WITH PARSER parser_name
| COMMENT 'string'
| CLUSTERING={YES| NO}
table_options:
table_option [[,] table_option] ...
In MariaDB 10.0.2 and later, IF EXISTS and IF NOT EXISTS
clauses have been added for the following:
ADD COLUMN [IF NOT EXISTS]
ADD INDEX [IF NOT EXISTS]
ADD FOREIGN KEY [IF NOT EXISTS]
ADD PARTITION [IF NOT EXISTS]
CREATE INDEX [IF NOT EXISTS]
DROP COLUMN [IF EXISTS]
DROP INDEX [IF EXISTS]
DROP FOREIGN KEY [IF EXISTS]
DROP PARTITION [IF EXISTS]
CHANGE COLUMN [IF EXISTS]
MODIFY COLUMN [IF EXISTS]
DROP INDEX [IF EXISTS]
When IF EXISTS and IF NOT EXISTS are used in clauses,
queries will not
report errors when the condition is triggered for that
clause. A warning with
the same message text will be issued and the ALTER will move
on to the next
clause in the statement (or end if finished).
This was done in MDEV-318.
Description
-----------
ALTER TABLE enables you to change the structure of an
existing table.
For example, you can add or delete columns, create or
destroy indexes,
change the type of existing columns, or rename columns or
the table
itself. You can also change the comment for the table and
the storage engine of the
table.
If another connection is using the table, a metadata lock is
active, and this statement will wait until the lock is
released. This is also true for non-transactional tables.
When adding a UNIQUE index on a column (or a set of columns)
which have duplicated values, an error will be produced and
the statement will be stopped. To suppress the error and
force the creation of UNIQUE indexes, discarding duplicates,
the IGNORE option can be specified. This can be useful if a
column (or a set of columns) should be UNIQUE but it
contains duplicate values; however, this technique provides
no control on which rows are preserved and which are
deleted. Also, note that IGNORE is accepted but ignored in
ALTER TABLE ... EXCHANGE PARTITION statements.
This statement can also be used to rename a table. For
details see RENAME TABLE.
When an index is created, the storage engine may use a
configurable buffer in the process. Incrementing the buffer
speeds up the index creation. Aria and MyISAM allocate a
buffer whose size is defined by aria_sort_buffer_size or
myisam_sort_buffer_size, also used for REPAIR TABLE.
InnoDB/XtraDB allocates three buffers whose size is defined
by innodb_sort_buffer_size.
Privileges
Executing the ALTER TABLE statement generally requires at
least the ALTER privilege for the table or the database..
If you are renaming a table, then it also requires the DROP,
CREATE and INSERT privileges for the table or the database
as well.
Online DDL
In MariaDB 10.0 and later, online DDL is supported with the
ALGORITHM and LOCK clauses.
See InnoDB Online DDL Overview for more information on
online DDL with InnoDB.
ALTER ONLINE TABLE
ALTER ONLINE TABLE has also worked for partitioned tables
since MariaDB 10.0.11.
Online ALTER TABLE is available by executing the following:
ALTER ONLINE TABLE ...;
This statement has the following semantics:
In MariaDB 10.0.12 and later, this statement is equivalent
to the following:
ALTER TABLE ... LOCK=NONE;
See the LOCK alter specification for more information.
In MariaDB 10.0.11, this statement is equivalent to the
following:
ALTER TABLE ... ALGORITHM=INPLACE;
See the ALGORITHM alter specification for more information.
MariaDB until 10.0.10
In MariaDB 10.0.10 and before, this statement ensures that
the ALTER TABLE statement does not make a copy of the table.
WAIT/NOWAIT
Set the lock wait timeout. See WAIT and NOWAIT.
Column Definitions
See CREATE TABLE: Column Definitions for information about
column definitions.
Index Definitions
See CREATE TABLE: Index Definitions for information about
index definitions.
The CREATE INDEX and DROP INDEX statements can also be used
to add or remove an index.
Character Sets and Collations
CONVERT TO CHARACTER SET charset_name [COLLATE
collation_name]
[DEFAULT] CHARACTER SET [=] charset_name
[DEFAULT] COLLATE [=] collation_name
See Setting Character Sets and Collations for details on
setting the character sets and collations.
Alter Specifications
Table Options
See CREATE TABLE: Table Options for information about table
options.
ADD COLUMN
... ADD COLUMN [IF NOT EXISTS] (col_name
column_definition,...)
Adds a column to the table. The syntax is the same as in
CREATE TABLE.
If you are using IF NOT_EXISTS the column will not be added
if it was not there already. This is very useful when doing
scripts to modify tables.
The FIRST and AFTER clauses affect the physical order of
columns in the datafile. Use FIRST to add a column in the
first (leftmost) position, or AFTER followed by a column
name to add the new column in any other position. Note that,
nowadays, the physical position of a column is usually
irrelevant.
See also Instant ADD COLUMN for InnoDB.
DROP COLUMN
... DROP COLUMN [IF EXISTS] col_name [CASCADE|RESTRICT]
Drops the column from the table.
If you are using IF EXISTS you will not get an error if the
column didn't exist.
If the column is part of any index, the column will be
dropped from them, except if you add a new column with
identical name at the same time. The index will be dropped
if all columns from the index were dropped.
If the column was used in a view or trigger, you will get an
error next time the view or trigger is accessed.
Dropping a column that is part of a multi-column UNIQUE
constraint is not permitted. For example:
CREATE TABLE a (
a int,
b int,
primary key (a,b)
);
ALTER TABLE x DROP COLUMN a;
[42000][1072] Key column 'A' doesny�� 't exist in table
The reason is that dropping column a would result in the new
constraint that all values in column b be unique. In order
to drop the column, an explicit DROP PRIMARY KEY and ADD
PRIMARY KEY would be required. Up until MariaDB 10.2.7, the
column was dropped and the additional constraint applied,
resulting in the following structure:
ALTER TABLE x DROP COLUMN a;
Query OK, 0 rows affected (0.46 sec)
DESC x;
+-------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| b | int(11) | NO | PRI | NULL | |
+-------+---------+------+-----+---------+-------+
MariaDB 10.4.0 supports instant DROP COLUMN. DROP COLUMN of
an indexed column would imply DROP INDEX (and in the case of
a non-UNIQUE multi-column index, possibly ADD INDEX). These
will not be allowed with ALGORITHM=INSTANT, but unlike
before, they can be allowed with ALGORITHM=NOCOPY
RESTRICT and CASCADE are allowed to make porting from other
database systems easier. In MariaDB, they do nothing.
MODIFY COLUMN
Allows you to modify the type of a column. The column will
be at the same place as the original column and all indexes
on the column will be kept. Note that when modifying column,
you should specify all attributes for the new column.
CREATE TABLE t1 (a INT UNSIGNED AUTO_INCREMENT, PRIMARY
KEY((a));
ALTER TABLE t1 MODIFY a BIGINT UNSIGNED AUTO_INCREMENT;
CHANGE COLUMN
Works like MODIFY COLUMN except that you can also change the
name of the column. The column will be at the same place as
the original column and all index on the column will be
kept.
CREATE TABLE t1 (a INT UNSIGNED AUTO_INCREMENT, PRIMARY
KEY(a));
ALTER TABLE t1 CHANGE a b BIGINT UNSIGNED AUTO_INCREMENT;
ALTER COLUMN
This lets you change column options.
CREATE TABLE t1 (a INT UNSIGNED AUTO_INCREMENT, b
varchar(50), PRIMARY KEY(a));
ALTER TABLE t1 ALTER b SET DEFAULT 'hello';
ADD PRIMARY KEY
Add a primary key.
For PRIMARY KEY indexes, you can specify a name for the
index, but it is silently ignored, and the name of the index
is always PRIMARY.
See Getting Started with Indexes: Primary Key for more
information.
DROP PRIMARY KEY
Drop a primary key.
For PRIMARY KEY indexes, you can specify a name for the
index, but it is silently ignored, and the name of the index
is always PRIMARY.
See Getting Started with Indexes: Primary Key for more
information.
ADD FOREIGN KEY
Add a foreign key.
For FOREIGN KEY indexes, a reference definition must be
provided.
For FOREIGN KEY indexes, you can specify a name for the
constraint, using the CONSTRAINT keyword. That name will be
used in error messages.
First, you have to specify the name of the target (parent)
table and a column or a column list which must be indexed
and whose values must match to the foreign key's values.
The MATCH clause is accepted to improve the compatibility
with other DBMS's, but has no meaning in MariaDB. The ON
DELETE and ON UPDATE clauses specify what must be done when
a DELETE (or a REPLACE) statements attempts to delete a
referenced row from the parent table, and when an UPDATE
statement attempts to modify the referenced foreign key
columns in a parent table row, respectively. The following
options are allowed:
RESTRICT: The delete/update operation is not performed. The
statement terminates with a 1451 error (SQLSTATE '2300').
NO ACTION: Synonym for RESTRICT.
CASCADE: The delete/update operation is performed in both
tables.
SET NULL: The update or delete goes ahead in the parent
table, and the corresponding foreign key fields in the child
table are set to NULL. (They must not be defined as NOT NULL
for this to succeed).
MariaDB until 5.3
SET DEFAULT: This option is currently implemented only for
the PBXT storage engine, which is disabled by default and no
longer maintained. It sets the child table's foreign key
fields to their DEFAULT values when the referenced parent
table key entries are updated or deleted.
If either clause is omitted, the default behavior for the
omitted clause is RESTRICT.
See Foreign Keys for more information.
DROP FOREIGN KEY
Drop a foreign key.
See Foreign Keys for more information.
ADD INDEX
Add a plain index.
Plain indexes are regular indexes that are not unique, and
are not acting as a primary key or a foreign key. They are
also not the "specialized" FULLTEXT or SPATIAL indexes.
See Getting Started with Indexes: Plain Indexes for more
information.
DROP INDEX
Drop a plain index.
Plain indexes are regular indexes that are not unique, and
are not acting as a primary key or a foreign key. They are
also not the "specialized" FULLTEXT or SPATIAL indexes.
See Getting Started with Indexes: Plain Indexes for more
information.
ADD UNIQUE INDEX
Add a unique index.
The UNIQUE keyword means that the index will not accept
duplicated values, except for NULLs. An error will raise if
you try to insert duplicate values in a UNIQUE index.
For UNIQUE indexes, you can specify a name for the
constraint, using the CONSTRAINT keyword. That name will be
used in error messages.
See Getting Started with Indexes: Unique Index for more
information.
DROP UNIQUE INDEX
Drop a unique index.
The UNIQUE keyword means that the index will not accept
duplicated values, except for NULLs. An error will raise if
you try to insert duplicate values in a UNIQUE index.
For UNIQUE indexes, you can specify a name for the
constraint, using the CONSTRAINT keyword. That name will be
used in error messages.
See Getting Started with Indexes: Unique Index for more
information.
ADD FULLTEXT INDEX
Add a FULLTEXT index.
See Full-Text Indexes for more information.
DROP FULLTEXT INDEX
Drop a FULLTEXT index.
See Full-Text Indexes for more information.
ADD SPATIAL INDEX
Add a SPATIAL index.
See SPATIAL INDEX for more information.
DROP SPATIAL INDEX
Drop a SPATIAL index.
See SPATIAL INDEX for more information.
ENABLE/ DISABLE KEYS
DISABLE KEYS will disable all non unique keys for the table
for storage engines that support this (at least MyISAM and
Aria). This can be used to speed up inserts into empty
tables.
ENABLE KEYS will enable all disabled keys.
RENAME TO
Renames the table. See also RENAME TABLE.
ADD CONSTRAINT
Modifies the table adding a constraint on a particular
column or columns.
MariaDB 10.2.1 introduced new ways to define a constraint.
Note: Before MariaDB 10.2.1, constraint expressions were
accepted in syntax, but ignored.
ALTER TABLE table_name
ADD CONSTRAINT [constraint_name] CHECK(expression);
Before a row is inserted or updated, all constraints are
evaluated in the order they are defined. If any constraint
fails, then the row will not be updated. One can use most
deterministic functions in a constraint, including UDF's.
CREATE TABLE account_ledger (
id INT PRIMARY KEY AUTO_INCREMENT,
transaction_name VARCHAR(100),
credit_account VARCHAR(100),
credit_amount INT,
debit_account VARCHAR(100),
debit_amount INT);
ALTER TABLE account_ledger
ADD CONSTRAINT is_balanced
CHECK((debit_amount + credit_amount) = 0);
The constraint_name is optional. If you don't provide one
in the ALTER TABLE statement, MariaDB auto-generates a name
for you. This is done so that you can remove it later using
DROP CONSTRAINT clause.
You can disable all constraint expression checks by setting
the variable check_constraint_checks to OFF. You may find
this useful when loading a table that violates some
constraints that you want to later find and fix in SQL.
To view constraints on a table, query
information_schema.TABLE_CONSTRAINTS:
SELECT CONSTRAINT_NAME, TABLE_NAME, CONSTRAINT_TYPE
FROM information_schema.TABLE_CONSTRAINTS
WHERE TABLE_NAME = 'account_ledger';
+-----------------+----------------+-----------------+
| CONSTRAINT_NAME | TABLE_NAME | CONSTRAINT_TYPE |
+-----------------+----------------+-----------------+
| is_balanced | account_ledger | CHECK |
+-----------------+----------------+-----------------+
DROP CONSTRAINT
DROP CONSTRAINT for UNIQUE and FOREIGN KEY constraints was
introduced in MariaDB 10.2.22 and MariaDB 10.w��� 3.13.
DROP CONSTRAINT for CHECK constraints was introduced in
MariaDB 10.2.1
Modifies the table, removing the given constraint.
ALTER TABLE table_name
DROP CONSTRAINT constraint_name;
When you add a constraint to a table, whether through a
CREATE TABLE or ALTER TABLE...ADD CONSTRAINT statement, you
can either set a constraint_name yourself, or allow MariaDB
to auto-generate one for you. To view constraints on a
table, query information_schema.TABLE_CONSTRAINTS. For
instance,
CREATE TABLE t (
a INT,
b INT,
c INT,
CONSTRAINT CHECK(a > b),
CONSTRAINT check_equals CHECK(a = c));
SELECT CONSTRAINT_NAME, TABLE_NAME, CONSTRAINT_TYPE
FROM information_schema.TABLE_CONSTRAINTS
WHERE TABLE_NAME = 't';
+-----------------+----------------+-----------------+
| CONSTRAINT_NAME | TABLE_NAME | CONSTRAINT_TYPE |
+-----------------+----------------+-----------------+
| check_equals | t | CHECK |
| CONSTRAINT_1 | t | CHECK |
+-----------------+----------------+-----------------+
To remove a constraint from the table, issue an ALTER
TABLE...DROP CONSTRAINT statement. For example,
ALTER TABLE t DROP CONSTRAINT is_unique;
ADD SYSTEM VERSIONING
System-versioned tables was added in MariaDB 10.3.4.
Add system versioning.
DROP SYSTEM VERSIONING
System-versioned tables was added in MariaDB 10.3.4.
Drop system versioning.
ADD PERIOD FOR SYSTEM_TIME
System-versioned tables was added in MariaDB 10.3.4.
FORCE
ALTER TABLE ... FORCE can force MariaDB to re-build the
table.
In MariaDB 5.5 and before, this could only be done by
setting the ENGINE table option to its old value. For
example, for an InnoDB table, one could execute the
following:
ALTER TABLE tab_name ENGINE = InnoDB;
In MariaDB 10.0 and later, the FORCE option can be used
instead. For example, :
ALTER TABLE tab_name FORCE;
With InnoDB, the table rebuild will only reclaim unused
space (i.e. the space previously used for deleted rows) if
the innodb_file_per_table system variable is set to ON. If
the system variable is OFF, then the space will not be
reclaimed, but it will be-re-used for new data that's later
added.
EXCHANGE PARTITION
ALTER TABLE ... EXCHANGE PARTITION was introduced in MariaDB
10.0.4
This is used to exchange the tablespace files between a
partition and another table.
See copying InnoDB's transportable tablespaces for more
information.
DISCARD TABLESPACE
This is used to discard an InnoDB table's tablespace.
See copying InnoDB's transportable tablespaces for more
information.
IMPORT TABLESPACE
This is used to import an InnoDB table's tablespace. The
tablespace should have been copied from its original server
after executing FLUSH TABLES FOR EXPORT.
See copying InnoDB's transportable tablespaces for more
information.
ALTER TABLE ... IMPORT only applies to InnoDB tables. Most
other popular storage engines, such as Aria and MyISAM, will
recognize their data files as soon as they've been placed
in the proper directory under the datadir, and no special
DDL is required to import them.
ALGORITHM
In MariaDB 5.5 and before, ALTER TABLE operations required
making a temporary copy of the table, which can be slow for
large tables.
In MariaDB 10.0 and later, the ALTER TABLE statement
supports the ALGORITHM clause. This clause is one of the
clauses that is used to implement online DDL. ALTER TABLE
supports several different algorithms. An algorithm can be
explicitly chosen for an ALTER TABLE operation by setting
the ALGORITHM clause. The supported values are:
ALGORITHM=DEFAULT - This implies the default behavior for
the specific statement, such as if no ALGORITHM clause is
specified.
ALGORITHM=COPY
ALGORITHM=INPLACE
ALGORITHM=NOCOPY - This was added in MariaDB 10.3.7.
ALGORITHM=INSTANT - This was added in MariaDB 10.3.7.
See InnoDB Online DDL Overview: ALGORITHM for information on
how the ALGORITHM clause affects InnoDB.
ALGORITHM=DEFAULT
The default behavior, which occurs if ALGORITHM=DEFAULT is
specified, or if ALGORITHM is not specified at all, usually
only makes a copy if the operation doesn't support being
done in-place at all. In this case, the most efficient
available algorithm will usually be used.
However, in MariaDB 10.3.6 and before, if the value of the
old_alter_table system variable is set to ON, then the
default behavior is to perform ALTER TABLE operations by
making a copy of the table using the old algorithm.
In MariaDB 10.3.7 and later, the old_alter_table system
variable is deprecated. Instead, the alter_algorithm system
variable defines the default algorithm for ALTER TABLE
operations.
ALGORITHM=COPY
ALGORITHM=COPY was introduced in MariaDB 10.0 as the name
for the original ALTER TABLE algorithm.
When ALGORITHM=COPY is set, MariaDB essentially does the
following operations:
-- Create a temporary table with the new definition
CREATE TEMPORARY TABLE tmp_tab (
...
);
-- Copy the data from the original table
INSERT INTO tmp_tab
SELECT * FROM original_tab;
-- Drop the original table
DROP TABLE original_tab;
-- Rename the temporary table, so that it replaces the
original one
RENAME TABLE tmp_tab TO original_tab;
This algorithm is very inefficient, but it is generic, so it
works for all storage engines.
If ALGORITHM=COPY is specified, then the copy algorithm will
be used even if it is not necessary. This can result in a
lengthy table copy. If multiple ALTER TABLE operations are
required that each require the table to be rebuilt, then it
is best to specify all operations in a single ALTER TABLE
statement, so that the table is only rebuilt once.
ALGORITHM=INPLACE
ALGORITHM=INPLACE was introduced in MariaDB 10.0.
ALGORITHM=COPY can be incredibly slow, because the whole
table has to be copied and rebuilt. ALGORITHM=INPLACE was
introduced as a way to avoid this by performing operations
in-place and avoiding the table copy and rebuild, when
possible.
When ALGORITHM=INPLACE is set, the underlying storage engine
uses optimizations to perform the operation while avoiding
the table copy and rebuild. However, INPLACE is a bit of a
misnomer, since some operations may still require the table
to be rebuilt for some storage engines. Regardless, several
operations can be performed without a full copy of the table
for some storage engines.
A more accurate name would have been ALGORITHM=ENGINE, where
ENGINE refers to an "engine-specific" algorithm.
If an ALTER TABLE operation supports ALGORITHM=INPLACE, then
it can be performed using optimizations by the underlying
storage engine, but it may rebuilt.
See InnoDB Online DDL Operations with ALGORITHM=INPLACE for
more.
ALGORITHM=NOCOPY
ALGORITHM=NOCOPY was introduced in MariaDB 10.3.7.
ALGORITHM=INPLACE can sometimes be surprisingly slow in
instances where it has to rebuild the clustered index,
because when the clustered index has to be rebuilt, the
whole table has to be rebuilt. ALGORITHM=NOCOPY was
introduced as a way to avoid this.
If an ALTER TABLE operation supports ALGORITHM=NOCOPY, then
it can be performed without rebuilding the clustered index.
If ALGORITHM=NOCOPY is specified for an ALTER TABLE
operation that does not support ALGORITHM=NOCOPY, then an
error will be raised. In this case, raising an error is
preferable, if the alternative is for the operation to
rebuild the clustered index, and perform unexpectedly
slowly.
See InnoDB Online DDL Operations with ALGORITHM=NOCOPY for
more.
ALGORITHM=INSTANT
ALGORITHM=INSTANT was introduced in MariaDB 10.3.7.
ALGORITHM=INPLACE can sometimes be surprisingly slow in
instances where it has to modify data files.
ALGORITHM=INSTANT was introduced as a way to avoid this.
If an ALTER TABLE operation supports ALGORITHM=INSTANT, then
it can be performed without modifying any data files.
If ALGORITHM=INSTANT is specified for an ALTER TABLE
operation that does not support ALGORITHM=INSTANT, then an
error will be raised. In this case, raising an error is
preferable, if the alternative is for the operation to
modify data files, and perform unexpectedly slowly.
See InnoDB Online DDL Operations with ALGORITHM=INSTANT for
more.
LOCK
In MariaDB 10.0 and later, the ALTER :�kN � TABLE statement
supports the LOCK clause. This clause is one of the clauses
that is used to implement online DDL. ALTER TABLE supports
several different locking strategies. A locking strategy can
be explicitly chosen for an ALTER TABLE operation by setting
the LOCK clause. The supported values are:
DEFAULT: Acquire the least restrictive lock on the table
that is supported for the specific operation. Permit the
maximum amount of concurrency that is supported for the
specific operation.
NONE: Acquire no lock on the table. Permit all concurrent
DML. If this locking strategy is not permitted for an
operation, then an error is raised.
SHARED: Acquire a read lock on the table. Permit read-only
concurrent DML. If this locking strategy is not permitted
for an operation, then an error is raised.
EXCLUSIVE: Acquire a write lock on the table. Do not permit
concurrent DML.
Different storage engines support different locking
strategies for different operations. If a specific locking
strategy is chosen for an ALTER TABLE operation, and that
table's storage engine does not support that locking
strategy for that specific operation, then an error will be
raised.
If the LOCK clause is not explicitly set, then the operation
uses LOCK=DEFAULT.
ALTER ONLINE TABLE is equivalent to LOCK=NONE. Therefore,
the ALTER ONLINE TABLE statement can be used to ensure that
your ALTER TABLE operation allows all concurrent DML.
See InnoDB Online DDL Overview: LOCK for information on how
the LOCK clause affects InnoDB.
Progress Reporting
MariaDB provides progress reporting for ALTER TABLE
statement for clients
that support the new progress reporting protocol. For
example, if you were using the mysql client, then the
progress report might look like this::
ALTER TABLE test ENGINE=Aria;
Stage: 1 of 2 'copy to tmp table' 46% of stage
The progress report is also shown in the output of the SHOW
PROCESSLIST statement and in the contents of the
information_schema.PROCESSLIST table.
See Progress Reporting for more information.
Aborting ALTER TABLE Operations
If an ALTER TABLE operation is being performed and the
connection is killed, the changes will be rolled back in a
controlled manner. The rollback can be a slow operation as
the time it takes is relative to how far the operation has
progressed.
Aborting ALTER TABLE ... ALGORITHM=COPY was made faster by
removing excessive undo logging (MDEV-11415). This
significantly shortens the time it takes to abort a running
ALTER TABLE operation.
Examples
--------
Adding a new column:
ALTER TABLE t1 ADD x INT;
Dropping a column:
ALTER TABLE t1 DROP x;
Modifying the type of a column:
ALTER TABLE t1 MODIFY x bigint unsigned;
Changing the name and type of a column:
ALTER TABLE t1 CHANGE a b bigint unsigned auto_increment;
Combining multiple clauses in a single ALTER TABLE
statement, separated by commas:
ALTER TABLE t1 DROP x, ADD x2 INT, CHANGE y y2 INT;
Changing the storage engine:
ALTER TABLE t1 ENGINE = InnoDB;
Rebuilding the table (the previous example will also rebuild
the table if it was already InnoDB):
ALTER TABLE t1 FORCE;
URL: https://mariadb.com/kb/en/alter-table/is function, the subselect will execute with your
privileges. As long as you have privileges to
select the salary of each employee, the caller of the
function will be able to get the maximum
salary for each department without being able to see
individual salaries.
Character sets and collations
Function return types can be declared to use any valid
character set and collation. If used, the COLLATE attribute
needs to be preceded by a CHARACTER SET attribute.
If the character set and collation are not specifically set
in the statement, the database defaults at the time of
creation will be used. If the database defaults change at a
later stage, the stored function character set/collation
will not be changed at the same time; the stored function
needs to be dropped and recreated to ensure the same
character set/collation as the database is used.
Examples
--------
The following example function takes a parameter, performs
an operation using
an SQL function, and returns the result.
CREATE FUNCTION hello (s CHAR(20))
RETURNS CHAR(50) DETERMINISTIC
RETURN CONCAT('Hello, ',s,'!');
SELECT hello('world');
+----------------+
| hello('world') |
+----------------+
| Hello, world! |
+----------------+
You can use a compound statement in a function to manipulate
data with statements
like INSERT and UPDATE. The following example creates a
counter function
that uses a temporary table to store the current value.
Because the compound statement
contains statements terminated with semicolons, you have to
first change the statement
delimiter with the DELIMITER statement to allow the
semicolon to be used in the
function body. See Delimiters in the mysql client for more.
CREATE TEMPORARY TABLE counter (c INT);
INSERT INTO counter VALUES (0);
DELIMITER //
CREATE FUNCTION counter () RETURNS INT
BEGIN
UPDATE counter SET c = c + 1;
RETURN (SELECT c FROM counter LIMIT 1);
END //
DELIMITER ;
Character set and collation:
CREATE FUNCTION hello2 (s CHAR(20))
RETURNS CHAR(50) CHARACTER SET 'utf8' COLLATE
'utf8_bin' DETERMINISTIC
RETURN CONCAT('Hello, ',s,'!');
URL: https://mariadb.com/kb/en/create-function/ x _ l t�U ��
�
% ' CONSTRAINTMariaDB supports the implementation of constraints at the
table-level using either CREATE TABLE or ALTER TABLE
statements. A table constraint restricts the data you can
add to the table. If you attempt to insert invalid data on a
column, MariaDB throws an error.
Syntax
------
[CONSTRAINT [symbol]] constraint_expression
constraint_expression:
| PRIMARY KEY [index_type] (index_col_name, ...)
[index_option] ...
| FOREIGN KEY [index_name] (index_col_name, ...)
REFERENCES tbl_name (index_col_name, ...)
[ON DELETE reference_option]
[ON UPDATE reference_option]
| UNIQUE [INDEX|KEY] [index_name]
[index_type] (index_col_name, ...) [index_option] ...
| CHECK (check_constraints)
index_type:
USING {BTREE | HASH | RTREE}
index_col_name:
col_name [(length)] [ASC | DESC]
index_option:
| KEY_BLOCK_SIZE [=] value
| index_type
| WITH PARSER parser_name
| COMMENT 'string'
| CLUSTERING={YES|NO}
reference_option:
RESTRICT | CASCADE | SET NULL | NO ACTION | SET DEFAULT
Description
-----------
Constraints provide restrictions on the data you can add to
a table. This allows you to enforce data integrity from
MariaDB, rather than through application logic. When a
statement violates a constraint, MariaDB throws an error.
There are four types of table constraints:
Constraint | Description |
PRIMARY KEY | Sets the column for referencing rows. Values
must be unique and not null. |
FOREIGN KEY | Sets the column to reference the primary key
on another table. |
UNIQUE | Requires values in column or columns only occur
once in the table. |
CHECK | Checks whether the data meets the given condition. |
FOREIGN KEY Constraints
InnoDB supports foreign key constraints. The syntax for a
foreign key
constraint definition in InnoDB looks like this:
[CONSTRAINT [symbol]] FOREIGN KEY
[index_name] (index_col_name, ...)
REFERENCES tbl_name (index_col_name,...)
[ON DELETE reference_option]
[ON UPDATE reference_option]
reference_option:
RESTRICT | CASCADE | SET NULL | NO ACTION
CHECK Constraints
From MariaDB 10.2.1, constraints are enforced. Before
MariaDB 10.2.1 constraint expressions were accepted in the
syntax but ignored.
In MariaDB 10.2.1 you can define constraints in 2 different
ways:
CHECK(expression) given as part of a column definition.
CONSTRAINT [constraint_name] CHECK (expression)
Before a row is inserted or updated, all constraints are
evaluated in the order they are defined. If any constraint
expression returns false, then the row will not be inserted
or updated.
One can use most deterministic functions in a constraint,
including UDFs.
CREATE TABLE t1 (a INT CHECK (a>2), b INT CHECK (b>2),
CONSTRAINT a_greater CHECK (a>b));
If you use the second format and you don't give a name to
the constraint, then the constraint will get an
automatically generated name. This is done so that you can
later delete the constraint with ALTER TABLE DROP
constraint_name.
One can disable all constraint expression checks by setting
the check_constraint_checks variable to OFF. This is useful
for example when loading a table that violates some
constraints that you want to later find and fix in SQL.
Replication
In row-based replication, only the master checks
constraints, and failed statements will not be replicated.
In statement-based replication, the slaves will also check
constraints. Constraints should therefore be identical, as
well as deterministic, in a replication environment.
Auto_increment
From MariaDB 10.2.6, auto_increment columns are no longer
permitted in check constraints. Previously they were
permitted, but would not work correctly. See MDEV-11117.
Examples
--------
CREATE TABLE product (category INT NOT NULL, id INT NOT
NULL,
price DECIMAL,
PRIMARY KEY(category, id)) ENGINE=INNODB;
CREATE TABLE customer (id INT NOT NULL,
PRIMARY KEY (id)) ENGINE=INNODB;
CREATE TABLE product_order (no INT NOT NULL AUTO_INCREMENT,
product_category INT NOT NULL,
product_id INT NOT NULL,
customer_id INT NOT NULL,
PRIMARY KEY(no),
INDEX (product_category, product_id),
FOREIGN KEY (product_category, product_id)
REFERENCES product(category, id)
ON UPDATE CASCADE ON DELETE RESTRICT,
INDEX (customer_id),
FOREIGN KEY (customer_id)
REFERENCES customer(id)) ENGINE=INNODB;
The following examples will work from MariaDB 10.2.1
onwards.
Numeric constraints and comparisons:
CREATE TABLE t1 (a INT CHECK (a>2), b INT CHECK (b>2),
CONSTRAINT a_greater CHECK (a>b));
INSERT INTO t1(a) VALUES (1);
ERROR 4022 (23000): CONSTRAINT `a` failed for `test`.`t1`
INSERT INTO t1(a,b) VALUES (3,4);
ERROR 4022 (23000): CONSTRAINT `a_greater` failed for
`test`.`t1`
INSERT INTO t1(a,b) VALUES (4,3);
Query OK, 1 row affected (0.04 sec)
Dropping a constraint:
ALTER TABLE t1 DROP CONSTRAINT a_greater;
Adding a constraint:
ALTER TABLE t1 ADD CONSTRAINT a_greater CHECK (a>b);
Date comparisons and character length:
CREATE TABLE t2 (name VARCHAR(30) CHECK
(CHAR_LENGTH(name)>2), start_date DATE,
end_date DATE CHECK (start_date IS NULL OR end_date IS NULL
OR start_date2)), start_date DATE,
end_date DATE CHECK (start_date IS NULL OR end_date IS NULL
OR start_date2 is very different to CHAR_LENGTH(name>2) as
the latter mistakenly performs a numeric comparison on the
name field, leading to unexpected results.
URL: https://mariadb.com/kb/en/constraint/https://mariadb.com/kb/en/constraint/ B�{�@ �3 � x ' ' CREATE EVENTSyntax
------
CREATE [OR REPLACE]
[DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
EVENT
[IF NOT EXISTS]
event_name
ON SCHEDULE schedule
[ON COMPLETION [NOT] PRESERVE]
[ENABLE | DISABLE | DISABLE ON SLAVE]
[COMMENT 'comment']
DO sql_statement;
schedule:
AT timestamp [+ INTERVAL interval] ...
| EVERY interval
[STARTS timestamp [+ INTERVAL interval] ...]
[ENDS timestamp [+ INTERVAL interval] ...]
interval:
quantity {YEAR | QUARTER | MONTH | DAY | HOUR | MINUTE |
WEEK | SECOND | YEAR_MONTH | DAY_HOUR | DAY_MINUTE |
DAY_SECOND | HOUR_MINUTE | HOUR_SECOND | MINUTE_SECOND}
Description
-----------
This statement creates and schedules a new event. It
requires the
EVENT privilege for the schema in which the event is to be
created.
The minimum requirements for a valid CREATE EVENT statement
are as
follows:
The keywords CREATE EVENT plus an event name, which uniquely
identifies
the event in the current schema. (Prior to MySQL 5.1.12,
the event name
needed to be unique only among events created by the same
user on a given
database.)
An ON SCHEDULE clause, which determines when and how often
the event
executes.
A DO clause, which contains the SQL statement to be executed
by an
event.
Here is an example of a minimal CREATE EVENT statement:
CREATE EVENT myevent
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
DO
UPDATE myschema.mytable SET mycol = mycol + 1;
The previous statement creates an event named myevent. This
event executes once
— one hour following its creation
— by running an SQL statement that increments the
value of the myschema.mytable table's mycol column by 1.
The event_name must be a valid MariaDB identifier with a
maximum length
of 64 characters. It may be delimited using back ticks, and
may be
qualified with the name of a database schema. An event is
associated
with both a MariaDB user (the definer) and a schema, and its
name must
be unique among names of events within that schema. In
general, the
rules governing event names are the same as those for names
of stored
routines. See Identifier Names.
If no schema is indicated as part of event_name, the default
(current)
schema is assumed.
For valid identifiers to use as event names, see Identifier
Names.
OR REPLACE
The OR REPLACE clause was included in MariaDB 10.1.4. If
used and the event already exists, instead of an error being
returned, the existing event will be dropped and replaced by
the newly defined event.
IF NOT EXISTS
If the IF NOT EXISTS clause is used, MariaDB will return a
warning instead of an error if the event already exists.
Cannot be used together with OR REPLACE.
ON SCHEDULE
The ON SCHEDULE clause can be used to specify when the event
must be triggered.
AT
If you want to execute the event only once (one time event),
you can use the AT keyword, followed by a timestamp. If you
use CURRENT_TIMESTAMP, the event acts as soon as it is
created. As a convenience, you can add one or more intervals
to that timestamp. You can also specify a timestamp in the
past, so that the event is stored but not triggered, until
you modify it via ALTER EVENT.
The following example shows how to create an event that will
be triggered tomorrow at a certain time:
CREATE EVENT example
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 DAY + INTERVAL
3 HOUR
DO something;
You can also specify that an event must be triggered at a
regular interval (recurring event). In such cases, use the
EVERY clause followed by the interval.
If an event is recurring, you can specify when the first
execution must happen via the STARTS clause and a maximum
time for the last execution via the ENDS clause. STARTS and
ENDS clauses are followed by a timestamp and, optionally,
one or more intervals. The ENDS clause can specify a
timestamp in the past, so that the event is stored but not
executed until you modify it via ALTER EVENT.
In the following example, next month a recurring event will
be triggered hourly for a week:
CREATE EVENT example
ON SCHEDULE EVERY 1 HOUR
STARTS CURRENT_TIMESTAMP + INTERVAL 1 MONTH
ENDS CURRENT_TIMESTAMP + INTERVAL 1 MONTH + INTERVAL 1 WEEK
DO some_task;
Intervals consist of a quantity and a time unit. The time
units are the same used for other staments and time
functions, except that you can't use microseconds for
events. For simple time units, like HOUR or MINUTE, the
quantity is an integer number, for example '10 MINUTE'.
For composite time units, like HOUR_MINUTE or HOUR_SECOND,
the quantity must be a string with all involved simple
values and their separators, for example '2:30' or
'2:30:30'.
ON COMPLETION [NOT] PRESERVE
The ON COMPLETION clause can be used to specify if the event
must be deleted after its last execution (that is, after its
AT or ENDS timestamp is past). By default, events are
dropped when they are expired. To explicitly state that this
is the desired behaviour, you can use ON COMPLETION NOT
PRESERVE. Instead, if you want the event to be preserved,
you can use ON COMPLETION PRESERVE.
In you specify ON COMPLETION NOT PRESERVE, and you specify a
timestamp in the past for AT or ENDS clause, the event will
be immediatly dropped. In such cases, you will get a Note
1558: "Event execution time is in the past and ON
COMPLETION NOT PRESERVE is set. The event was dropped
immediately after creation".
ENABLE/DISABLE/DISABLE ON SLAVE
Events are ENABLEd by default. If you want to stop MariaDB
from executing
an event, you may specify DISABLE. When it is ready to be
activated, you
may enable it using ALTER EVENT. Another option is
DISABLE ON SLAVE, which indicates that an event was created
on a master and has been replicated to the slave, which is
prevented from executing the event. If DISABLE ON SLAVE is
specifically set, the event will not be executed.
COMMENT
The COMMENT clause may be used to set a comment for the
event. Maximum
length for comments is 64 characters. The comment is a
string, so it must be
quoted. To see events comments, you can query the
INFORMATION_SCHEMA.EVENTS table (the column is named
EVENT_COMMENT).
Examples
--------
Minimal CREATE EVENT statement:
CREATE EVENT myevent
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
DO
UPDATE myschema.mytable SET mycol = mycol + 1;
An event that will be triggered tomorrow at a certain time:
CREATE EVENT example
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 DAY + INTERVAL
3 HOUR
DO something;
Next month a recurring event will be triggered hourly for a
week:
CREATE EVENT example
ON SCHEDULE EVERY 1 HOUR
STARTS CURRENT_TIMESTAMP + INTERVAL 1 MONTH
ENDS CURRENT_TIMESTAMP + INTERVAL 1 MONTH + INTERVAL 1 WEEK
DO some_task;
OR REPLACE and IF NOT EXISTS:
CREATE EVENT myevent
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
DO
UPDATE myschema.mytable SET mycol = mycol + 1;
ERROR 1537 (HY000): Event 'myevent' already exists
CREATE OR REPLACE EVENT myevent
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
DO
UPDATE myschema.mytable SET mycol = mycol + 1;;
Query OK, 0 rows affected (0.00 sec)
CREATE EVENT IF NOT EXISTS myevent
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
DO
UPDATE myschema.mytable SET mycol = mycol + 1;
Query OK, 0 rows affected, 1 warning (0.00 sec)
SHOW WARNINGS;
+-------+------+--------------------------------+
| Level | Code | Message |
+-------+------+--------------------------------+
| Note | 1537 | Event 'myevent' already exists |
+-------+------+--------------------------------+
URL: https://mariadb.com/kb/en/create-event/https://mariadb.com/kb/en/create-event/ � ou�p Syntax
------
CREATE [OR REPLACE]
[DEFINER = {user | CURRENT_USER | role | CURRENT_ROLE }]
[AGGREGATE] FUNCTION [IF NOT EXISTS] func_name
([func_parameter[,...]])
RETURNS type
[characteristic ...]
RETURN func_body
func_parameter:
param_name type
type:
Any valid MariaDB data type
characteristic:
LANGUAGE SQL
| [NOT] DETERMINISTIC
| { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL
DATA }
| SQL SECURITY { DEFINER | INVOKER }
| COMMENT 'string'
func_body:
Valid SQL procedure statement
Description
-----------
Use the CREATE FUNCTION statement to create a new stored
function. You must have
the CREATE ROUTINE database privilege to use CREATE
FUNCTION.
A function takes any number of arguments and returns a value
from the function body. The
function body can be any valid SQL expression as you would
use, for example, in any select
expression. If you have the appropriate privileges, you can
call the function exactly as you
would any built-in function. See Security below for details
on privileges.
You can also use a variant of the CREATE FUNCTION statement
to install a user-defined
function (UDF) defined by a plugin. See CREATE FUNCTION
(UDF)
for details.
You can use a SELECT statement for the function body by
enclosing it in
parentheses, exactly as you would to use a subselect for any
other expression. The SELECT
statement must return a single value. If more than one
column is returned when the function is called,
error 1241 results. If more than one row is returned when
the function is called, error 1242
results. Use a LIMIT clause to ensure only one row is
returned.
You can also replace the RETURN clause with a BEGIN...END
compound
statement. The compound statement must contain a RETURN
statement. When the function is
called, the RETURN statement immediately returns its result,
and any statements after RETURN
are effectively ignored.
By default, a function is associated with the default
database. To associate the function explicitly
with a given database, specify the fully-qualified name as
db_name.func_name
when you create it. If the function name is the same as the
name of a built-in function, you must
use the fully qualified name when you call it.
The parameter list enclosed within parentheses must always
be present.
If there are no parameters, an empty parameter list of ()
should be
used. Parameter names are not case sensitive.
Each parameter can be declared to use any valid data type,
except that
the COLLATE attribute cannot be used.
For valid identifiers to use as function names, see
Identifier Names.
AGGREGATE
From MariaDB 10.3.3, it is possible to create stored
aggregate functions as well. See Stored Aggregate Functions
for details.
RETURNS
The RETURNS clause specifies the return type of the
function. NULL values are permitted with all return types.
What happens if the RETURN clause returns a value of a
different type? It depends on the SQL_MODE in effect at the
moment of the function creation.
If the SQL_MODE is strict (STRICT_ALL_TABLES or
STRICT_TRANS_TABLES flags are specified), a 1366 error will
be produced.
Otherwise, the value is coerced to the proper type. For
example, if a function
specifies an ENUM or SET value in the RETURNS clause, but
the RETURN
clause returns an integer, the value returned from the
function is the string for the corresponding ENUM
member of set of SET members.
MariaDB stores the SQL_MODE system variable setting that is
in effect at the
time a routine is created, and always executes the routine
with this setting in
force, regardless of the server SQL mode in effect when the
routine is invoked.
LANGUAGE SQL
LANGUAGE SQL is a standard SQL clause, and it can be used in
MariaDB for portability. However that clause has no meaning,
because SQL is the only supported language for stored
functions.
A function is deterministic if it can produce only one
result for a given list of parameters. If the result may be
affected by stored data, server variables, random numbers or
any value that is not explicitly passed, then the function
is not deterministic. Also, a function is non-deterministic
if it uses non-deterministic functions like NOW() or
CURRENT_TIMESTAMP(). The optimizer may choose a faster
execution plan if it known that the function is
deterministic. In such cases, you should declare the routine
using the DETERMINISTIC keyword. If you want to explicitly
state that the function is not deterministic (which is the
default) you can use the NOT DETERMINISTIC keywords.
If you declare a non-deterministic function as
DETERMINISTIC, you may get incorrect results. If you declare
a deterministic function as NOT DETERMINISTIC, in some cases
the queries will be slower.
OR REPLACE
If the optional OR REPLACE clause is used, it acts as a
shortcut for:
DROP FUNCTION IF EXISTS function_name;
CREATE FUNCTION function_name ...;
with the exception that any existing privileges for the
function are not dropped.
IF NOT EXISTS
If the IF NOT EXISTS clause is used, MariaDB will return a
warning instead of an error if the function already exists.
Cannot be used together with OR REPLACE.
[NOT] DETERMINISTIC
The [NOT] DETERMINISTIC clause also affects binary logging,
because the STATEMENT format can not be used to store or
replicate non-deterministic statements.
CONTAINS SQL, NO SQL, READS SQL DATA, and MODIFIES SQL DATA
are informative clauses that tell the server what the
function does. MariaDB does not check in any way whether the
specified clause is correct. If none of these clauses are
specified, CONTAINS SQL is used by default.
MODIFIES SQL DATA
MODIFIES SQL DATA means that the function contains
statements that may modify data stored in databases. This
happens if the function contains statements like DELETE,
UPDATE, INSERT, REPLACE or DDL.
READS SQL DATA
READS SQL DATA means that the function reads data stored in
databases, but does not modify any data. This happens if
SELECT statements are used, but there no write operations
are executed.
CONTAINS SQL
CONTAINS SQL means that the function contains at least one
SQL statement, but it does not read or write any data stored
in a database. Examples include SET or DO.
NO SQL
NO SQL means nothing, because MariaDB does not currently
support any language other than SQL.
Oracle Mode
From MariaDB 10.3, a subset of Oracle's PL/SQL language has
been supported in addition to the traditional SQL/PSM-based
MariaDB syntax. See Oracle mode from MariaDB 10.3 for
details on changes when running Oracle mode.
Security
You must have the EXECUTE privilege on a function to call
it.
MariaDB automatically grants the EXECUTE and ALTER ROUTINE
privileges to the
account that called CREATE FUNCTION, even if the DEFINER
clause was used.
Each function has an account associated as the definer. By
default, the definer is the account
that created the function. Use the DEFINER clause to specify
a different account as the
definer. You must have the SUPER privilege to use the
DEFINER
clause. See Account Names for details on specifying
accounts.
The SQL SECURITY clause specifies what privileges are used
when a function is called.
If SQL SECURITY is INVOKER, the function body will be
evaluated using the privileges
of the user calling the function. If SQL SECURITY is
DEFINER, the function body is
always evaluated using the privileges of the definer
account. DEFINER is the default.
This allows you to create functions that grant limited
access to certain data. For example, say
you have a table that stores some employee information, and
that you've granted SELECT
privileges only on certain columns to the user account
roger.
CREATE TABLE employees (name TINYTEXT, dept TINYTEXT, salary
INT);
GRANT SELECT (name, dept) ON employees TO roger;
To allow the user the get the maximum salary for a
department, define a function and grant
the EXECUTE privilege:
CREATE FUNCTION max_salary (dept TINYTEXT) RETURNS INT
RETURN
(SELECT MAX(salary) FROM employees WHERE employees.dept =
dept);
GRANT EXECUTE ON FUNCTION max_salary TO roger;
Since SQL SECURITY defaults to DEFINER, whenever the user
roger calls
th� �J � �
' ' CREATE INDEXSyntax
------
CREATE [OR REPLACE] [UNIQUE|FULLTEXT|SPATIAL] INDEX
[IF NOT EXISTS] index_name
[index_type]
ON tbl_name (index_col_name,...)
[WAIT n | NOWAIT]
[index_option]
[algorithm_option | lock_option] ...
index_col_name:
col_name [(length)] [ASC | DESC]
index_type:
USING {BTREE | HASH | RTREE}
index_option:
KEY_BLOCK_SIZE [=] value
| index_type
| WITH PARSER parser_name
| COMMENT 'string'
algorithm_option:
ALGORITHM [=] {DEFAULT|INPLACE|COPY|NOCOPY|INSTANT}
lock_option:
LOCK [=] {DEFAULT|NONE|SHARED|EXCLUSIVE}
Description
-----------
CREATE INDEX is mapped to an ALTER TABLE statement to create
indexes.
See ALTER TABLE. CREATE INDEX cannot be used to create a
PRIMARY KEY; use ALTER TABLE instead.
If another connection is using the table, a metadata lock is
active, and this statement will wait until the lock is
released. This is also true for non-transactional tables.
Another shortcut, DROP INDEX, allows the removal of an
index.
For valid identifiers to use as index names, see Identifier
Names.
Note that KEY_BLOCK_SIZE is currently ignored in CREATE
INDEX, although it is included in the output of SHOW CREATE
TABLE.
Privileges
Executing the CREATE INDEX statement requires the INDEX
privilege for the table or the database.
Online DDL
In MariaDB 10.0 and later, online DDL is supported with the
ALGORITHM and LOCK clauses.
See InnoDB Online DDL Overview for more information on
online DDL with InnoDB.
CREATE OR REPLACE INDEX ...
The OR REPLACE clause was added in MariaDB 10.1.4.
If the OR REPLACE clause is used and if the index already
exists, then instead of returning an error, the server will
drop the existing index and replace it with the newly
defined index.
CREATE INDEX IF NOT EXISTS ...
If the IF NOT EXISTS clause is used, then the index will
only be created if an index with the same name does not
already exist. If the index already exists, then a warning
will be triggered by default.
Index Definitions
See CREATE TABLE: Index Definitions for information about
index definitions.
WAIT/NOWAIT
Set the lock wait timeout. See WAIT and NOWAIT.
ALGORITHM
See ALTER TABLE: ALGORITHM for more information.
LOCK
See ALTER TABLE: LOCK for more information.
Progress Reporting
MariaDB provides progress reporting for CREATE INDEX
statement for clients
that support the new progress reporting protocol. For
example, if you were using the mysql client, then the
progress report might look like this::
CREATE INDEX ON tab (num);;
Stage: 1 of 2 'copy to tmp table' 46% of stage
The progress report is also shown in the output of the SHOW
PROCESSLIST statement and in the contents of the
information_schema.PROCESSLIST table.
See Progress Reporting for more information.
Examples
--------
Creating a unique index:
CREATE UNIQUE INDEX HomePhone ON Employees(Home_Phone);
OR REPLACE and IF NOT EXISTS:
CREATE INDEX xi ON xx5 (x);
Query OK, 0 rows affected (0.03 sec)
CREATE INDEX xi ON xx5 (x);
ERROR 1061 (42000): Duplicate key name 'xi'
CREATE OR REPLACE INDEX xi ON xx5 (x);
Query OK, 0 rows affected (0.03 sec)
CREATE INDEX IF NOT EXISTS xi ON xx5 (x);
Query OK, 0 rows affected, 1 warning (0.00 sec)
SHOW WARNINGS;
+-------+------+-------------------------+
| Level | Code | Message |
+-------+------+-------------------------+
| Note | 1061 | Duplicate key name 'xi' |
+-------+------+-------------------------+
URL: https://mariadb.com/kb/en/create-index/https://mariadb.com/kb/en/create-index/ � x * ' CREATE SEQUENCECREATE SEQUENCE was introduced in MariaDB 10.3.
Syntax
------
CREATE [OR REPLACE] [TEMPORARY] SEQUENCE [IF NOT EXISTS]
sequence_name
[ INCREMENT [ BY | = ] increment ]
[ MINVALUE [=] minvalue | NO MINVALUE | NOMINVALUE ]
[ MAXVALUE [=] maxvalue | NO MAXVALUE | NOMAXVALUE ]
[ START [ WITH | = ] start ]
[ CACHE [=] cache | NOCACHE ] [ CYCLE | NOCYCLE]
[table_options]
The options for CREATE SEQUENCE can be given in any order,
optionally followed by table_options.
table_options can be any of the normal table options in
CREATE TABLE but the most usable ones are ENGINE=... and
COMMENT=.
NOMAXVALUE and NOMINVALUE are there to allow one to create
SEQUENCEs using the Oracle syntax.
Description
-----------
CREATE SEQUENCE will create a sequence that generates new
values when called with NEXT VALUE FOR sequence_name. It's
an alternative to AUTO INCREMENT when one wants to have more
control of how the numbers are generated. As the SEQUENCE
caches values (up to CACHE) it can in some cases be much
faster than AUTO INCREMENT. Another benefit is that one can
access the last value generated by all used sequences, which
solves one of the limitations with LAST_INSERT_ID().
CREATE SEQUENCE requires the CREATE privilege.
DROP SEQUENCE can be used to drop a sequence, and ALTER
SEQUENCE to change it.
Arguments to Create
The following options may be used:
Option | Default value | Description |
INCREMENT | 1 | Increment to use for values. May be
negative. Setting an increment of 0 causes the sequence to
use the value of the auto_increment_increment system
variable at the time of creation, which is always a positive
number. (see MDEV-16035). |
MINVALUE | 1 if INCREMENT > 0 and -9223372036854775807 if
INCREMENT < 0 | Minimum value for the sequence |
MAXVALUE | 9223372036854775806 if INCREMENT > 0 and -1 if
INCREMENT < 0 | Max value for sequence |
START | MINVALUE if INCREMENT > 0 and MAX_VALUE if
INCREMENT< 0 | First value that the sequence will generate |
CACHE | 1000 | Number of values that should be cached. 0
if no CACHE. The underlying table will be updated first time
a new sequence number is generated and each time the cache
runs out. |
If CYCLE is used then the sequence should start again from
MINVALUE after it has run out of values. Default value is
NOCYCLE.
Constraints on Create Arguments
To be able to create a legal sequence, the following must
hold:
MAXVALUE >= start
MAXVALUE > MINVALUE
START >= MINVALUE
MAXVALUE = -9223372036854775807 (LONGLONG_MIN+1)
Note that sequences can't generate the maximum/minimum 64
bit number because of the constraint of
MINVALUE and MAXVALUE.
Examples
--------
CREATE SEQUENCE s START WITH 100 INCREMENT BY 10;
CREATE SEQUENCE s2 START WITH -100 INCREMENT BY -10;
The following statement fails, as the increment conflicts
with the defaults
CREATE SEQUENCE s3 START WITH -100 INCREMENT BY 10;
ERROR 4082 (HY000): Sequence 'test.s3' values are
conflicting
The sequence can be created by specifying workable minimum
and maximum values:
CREATE SEQUENCE s3 START WITH -100 INCREMENT BY 10
MINVALUE=-100 MAXVALUE=1000;
URL: https://mariadb.com/kb/en/create-sequence/https://mariadb.com/kb/en/create-sequence/ �
� �
�Y �4 � +. ' CREATE PACKAGE BODYOracle-style packages were introduced in MariaDB 10.3.5.
Syntax
------
CREATE [ OR REPLACE ]
[DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
PACKAGE BODY
[ IF NOT EXISTS ]
[ db_name . ] package_name
[ package_characteristic... ]
{ AS | IS }
package_implementation_declare_section
package_implementation_executable_section
END [ package_name]
package_implementation_declare_section:
package_implementation_item_declaration
[ package_implementation_item_declaration... ]
[ package_implementation_routine_definition... ]
| package_implementation_routine_definition
[ package_implementation_routine_definition...]
package_implementation_item_declaration:
variable_declaration ;
variable_declaration:
variable_name[,...] type [:= expr ]
package_implementation_routine_definition:
FUNCTION package_specification_function
[ package_implementation_function_body ] ;
| PROCEDURE package_specification_procedure
[ package_implementation_procedure_body ] ;
package_implementation_function_body:
{ AS | IS } package_routine_body [func_name]
package_implementation_procedure_body:
{ AS | IS } package_routine_body [proc_name]
package_routine_body:
[ package_routine_declarations ]
BEGIN
statements [ EXCEPTION exception_handlers ]
END
package_routine_declarations:
package_routine_declaration ';'
[package_routine_declaration ';']...
package_routine_declaration:
variable_declaration
| condition_name CONDITION FOR condition_value
| user_exception_name EXCEPTION
| CURSOR_SYM cursor_name
[ ( cursor_formal_parameters ) ]
IS select_statement
;
package_implementation_executable_section:
END
| BEGIN
statement ; [statement ; ]...
[EXCEPTION exception_handlers]
END
exception_handlers:
exception_handler [exception_handler...]
exception_handler:
WHEN_SYM condition_value [, condition_value]...
THEN_SYM statement ; [statement ;]...
condition_value:
condition_name
| user_exception_name
| SQLWARNING
| SQLEXCEPTION
| NOT FOUND
| OTHERS_SYM
| SQLSTATE [VALUE] sqlstate_value
| mariadb_error_code
Description
-----------
The CREATE PACKAGE BODY statement can be used when Oracle
SQL_MODE is set.
The CREATE PACKAGE BODY statement creates the package body
for a stored package. The package specification must be
previously created using the CREATE PACKAGE statement.
A package body provides implementations of the package
public routines and can optionally have:
package-wide private variables
package private routines
forward declarations for private routines
an executable initialization section
Examples
--------
SET sql_mode=ORACLE;
DELIMITER $$
CREATE OR REPLACE PACKAGE employee_tools AS
FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2);
PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2));
PROCEDURE raiseSalaryStd(eid INT);
PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2));
END;
$$
CREATE PACKAGE BODY employee_tools AS
-- package body variables
stdRaiseAmount DECIMAL(10,2):=500;
-- private routines
PROCEDURE log (eid INT, ecmnt TEXT) AS
BEGIN
INSERT INTO employee_log (id, cmnt) VALUES (eid, ecmnt);
END;
-- public routines
PROCEDURE hire(ename TEXT, esalary DECIMAL(10,2)) AS
eid INT;
BEGIN
INSERT INTO employee (name, salary) VALUES (ename,
esalary);
eid:= last_insert_id();
log(eid, 'hire ' || ename);
END;
FUNCTION getSalary(eid INT) RETURN DECIMAL(10,2) AS
nSalary DECIMAL(10,2);
BEGIN
SELECT salary INTO nSalary FROM employee WHERE id=eid;
log(eid, 'getSalary id=' || eid || ' salary=' ||
nSalary);
RETURN nSalary;
END;
PROCEDURE raiseSalary(eid INT, amount DECIMAL(10,2)) AS
BEGIN
UPDATE employee SET salary=salary+amount WHERE id=eid;
log(eid, 'raiseSalary id=' || eid || ' amount=' ||
amount);
END;
PROCEDURE raiseSalaryStd(eid INT) AS
BEGIN
raiseSalary(eid, stdRaiseAmount);
log(eid, 'raiseSalaryStd id=' || eid);
END;
BEGIN
-- This code is executed when the current session
-- accesses any of the package routines for the first time
log(0, 'Session ' || connection_id() || ' ' ||
current_user || ' started');
END;
$$
DELIMITER ;
URL: https://mariadb.com/kb/en/create-package-body/https://mariadb.com/kb/en/create-package-body/ �
�( ' DROP DATABASESyntax
------
DROP {DATABASE | SCHEMA} [IF EXISTS] db_name
Description
-----------
DROP DATABASE drops all tables in the database and deletes
the database. Be very careful with this statement! To use
DROP DATABASE,
you need the DROP privilege on the database. DROP SCHEMA is
a synonym for DROP DATABASE.
Important: When a database is dropped, user privileges on
the database are not automatically dropped. See GRANT.
IF EXISTS
Use IF EXISTS to prevent an error from occurring for
databases that do not exist. A NOTE is generated for each
non-existent database when using IF EXISTS. See SHOW
WARNINGS.
Examples
--------
DROP DATABASE bufg;
Query OK, 0 rows affected (0.39 sec)
DROP DATABASE bufg;
ERROR 1008 (HY000): Can't drop database 'bufg'; database
doesn't exist
\W
Show warnings enabled.
DROP DATABASE IF EXISTS bufg;
Query OK, 0 rows affected, 1 warning (0.00 sec)
Note (Code 1008): Can't drop database 'bufg'; database
doesn't exist
URL: https://mariadb.com/kb/en/drop-database/https://mariadb.com/kb/en/drop-database/ �: z?g Syntax
------
CREATE
[OR REPLACE]
[DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
PROCEDURE sp_name ([proc_parameter[,...]])
[characteristic ...] routine_body
proc_parameter:
[ IN | OUT | INOUT ] param_name type
type:
Any valid MariaDB data type
characteristic:
LANGUAGE SQL
| [NOT] DETERMINISTIC
| { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL
DATA }
| SQL SECURITY { DEFINER | INVOKER }
| COMMENT 'string'
routine_body:
Valid SQL procedure statement
Description
-----------
Creates a stored procedure. By default, a routine is
associated with the default database. To associate the
routine
explicitly with a given database, specify the name as
db_name.sp_name
when you create it.
When the routine is invoked, an implicit USE db_name is
performed (and
undone when the routine terminates). The causes the routine
to have
the given default database while it executes. USE statements
within
stored routines are disallowed.
When a stored procedure has been created, you invoke it by
using the CALL statement (see CALL).
To execute the CREATE PROCEDURE statement, it is
necessary to have the CREATE ROUTINE privilege. By default,
MariaDB
automatically grants the ALTER ROUTINE and EXECUTE
privileges to the
routine creator. See also Stored Routine Privileges.
The DEFINER and SQL SECURITY clauses specify the security
context to
be used when checking access privileges at routine execution
time, as
described later.
If the routine name is the same as the name of a built-in
SQL
function, you must use a space between the name and the
following
parenthesis when defining the routine, or a syntax error
occurs. This
is also true when you invoke the routine later. For this
reason, we
suggest that it is better to avoid re-using the names of
existing SQL
functions for your own stored routines.
The IGNORE_SPACE SQL mode applies to built-in functions, not
to stored
routines. It is always allowable to have spaces after a
routine name,
regardless of whether IGNORE_SPACE is enabled.
The parameter list enclosed within parentheses must always
be present.
If there are no parameters, an empty parameter list of ()
should be
used. Parameter names are not case sensitive.
Each parameter can be declared to use any valid data type,
except that
the COLLATE attribute cannot be used.
For valid identifiers to use as procedure names, see
Identifier Names.
IN/OUT/INOUT
Each parameter is an IN parameter by default. To specify
otherwise for
a parameter, use the keyword OUT or INOUT before the
parameter name.
An IN parameter passes a value into a procedure. The
procedure might
modify the value, but the modification is not visible to the
caller
when the procedure returns. An OUT parameter passes a value
from the
procedure back to the caller. Its initial value is NULL
within the
procedure, and its value is visible to the caller when the
procedure
returns. An INOUT parameter is initialized by the caller,
can be
modified by the procedure, and any change made by the
procedure is
visible to the caller when the procedure returns.
For each OUT or INOUT parameter, pass a user-defined
variable in the
CALL statement that invokes the procedure so that you can
obtain its
value when the procedure returns. If you are calling the
procedure
from within another stored procedure or function, you can
also pass a
routine parameter or local routine variable as an IN or
INOUT
parameter.
DETERMINISTIC/NOT DETERMINISTIC
DETERMINISTIC and NOT DETERMINISTIC apply only to functions.
Specifying DETERMINISTC or NON-DETERMINISTIC in procedures
has no effect. The default value is NOT DETERMINISTIC.
Functions are DETERMINISTIC when they always return the same
value for the same input. For example, a truncate or
substring function. Any function involving data, therefore,
is always NOT DETERMINISTIC.
CONTAINS SQL/NO SQL/READS SQL DATA/MODIFIES SQL DATA
CONTAINS SQL, NO SQL, READS SQL DATA, and MODIFIES SQL DATA
are informative clauses that tell the server what the
function does. MariaDB does not check in any way whether the
specified clause is correct. If none of these clauses are
specified, CONTAINS SQL is used by default.
MODIFIES SQL DATA means that the function contains
statements that may modify data stored in databases. This
happens if the function contains statements like DELETE,
UPDATE, INSERT, REPLACE or DDL.
READS SQL DATA means that the function reads data stored in
databases, but does not modify any data. This happens if
SELECT statements are used, but there no write operations
are executed.
CONTAINS SQL means that the function contains at least one
SQL statement, but it does not read or write any data stored
in a database. Examples include SET or DO.
NO SQL means nothing, because MariaDB does not currently
support any language other than SQL.
The routine_body consists of a valid SQL procedure
statement. This can
be a simple statement such as SELECT or INSERT, or it can be
a
compound statement written using BEGIN and END. Compound
statements
can contain declarations, loops, and other control structure
statements. See Programmatic and Compound Statements for
syntax details.
MariaDB allows routines to contain DDL statements, such as
CREATE and
DROP. MariaDB also allows stored procedures (but not stored
functions)
to contain SQL transaction statements such as COMMIT.
For additional information about statements that are not
allowed in
stored routines, see Stored Routine Limitations.
Invoking stored procedure from within programs
For information about invoking stored procedures from within
programs written in a language that has a MariaDB/MySQL
interface, see CALL.
OR REPLACE
If the optional OR REPLACE clause is used, it acts as a
shortcut for:
DROP PROCEDURE IF EXISTS name;
CREATE PROCEDURE name ...;
with the exception that any existing privileges for the
procedure are not dropped.
sql_mode
MariaDB stores the sql_mode system variable setting that is
in effect at the time a routine is created, and always
executes the routine with this setting in force, regardless
of the server SQL mode in effect when the routine is
invoked.
Character Sets and Collations
Procedure parameters can be declared with any character
set/collation. If the character set and collation are not
specifically set, the database defaults at the time of
creation will be used. If the database defaults change at a
later stage, the stored procedure character set/collation
will not be changed at the same time; the stored procedure
needs to be dropped and recreated to ensure the same
character set/collation as the database is used.
Oracle Mode
From MariaDB 10.3, a subset of Oracle's PL/SQL language has
been supported in addition to the traditional SQL/PSM-based
MariaDB syntax. See Oracle mode from MariaDB 10.3 for
details on changes when running Oracle mode.
Examples
--------
The following example shows a simple stored procedure that
uses an OUT
parameter. It uses the DELIMITER command to set a new
delimiter for the duration of the process — see Delimiters
in the mysql client.
DELIMITER //
CREATE PROCEDURE simpleproc (OUT param1 INT)
BEGIN
SELECT COUNT(*) INTO param1 FROM t;
END;
//
DELIMITER ;
CALL simpleproc(@a);
SELECT @a;
+------+
| @a |
+------+
| 1 |
+------+
Character set and collation:
DELIMITER //
CREATE PROCEDURE simpleproc2 (
OUT param1 CHAR(10) CHARACTER SET 'utf8' COLLATE
'utf8_bin'
)
BEGIN
SELECT CONCAT('a'),f1 INTO param1 FROM t;
END;
//
DELIMITER ;
CREATE OR REPLACE:
DELIMITER //
CREATE PROCEDURE simpleproc2 (
OUT param1 CHAR(10) CHARACTER SET 'utf8' COLLATE
'utf8_bin'
)
BEGIN
SELECT CONCAT('a'),f1 INTO param1 FROM t;
END;
//
ERROR 1304 (42000): PROCEDURE simpleproc2 already exists
DELIMITER ;
DELIMITER //
CREATE OR REPLACE PROCEDURE simpleproc2 (
OUT param1 CHAR(10) CHARACTER SET 'utf8' COLLATE
'utf8_bin'
)
BEGIN
SELECT CONCAT('a'),f1 INTO param1 FROM t;
END;
//
ERROR 1304 (42000): PROCEDURE simpleproc2 already exists
DELIMITER ;
Query OK, 0 rows affected (0.03 sec)
URL: https://mariadb.com/kb/en/create-procedure/ ^ �� �
,( ' CREATE SERVERSyntax
------
CREATE [OR REPLACE] SERVER [IF NOT EXISTS] server_name
FOREIGN DATA WRAPPER wrapper_name
OPTIONS (option [, option] ...)
option:
{ HOST character-literal
| DATABASE character-literal
| USER character-literal
| PASSWORD character-literal
| SOCKET character-literal
| OWNER character-literal
| PORT numeric-literal }
Description
-----------
This statement creates the definition of a server for use
with the Spider,
FEDERATED or FederatedX storage
engine. The CREATE SERVER statement creates a new row within
the
servers table within the mysql database. This statement
requires the SUPER privilege.
The server_name should be a unique reference to the server.
Server definitions
are global within the scope of the server, it is not
possible to qualify the
server definition to a specific database. server_name has a
maximum length of
64 characters (names longer than 64 characters are silently
truncated), and is
case insensitive. You may specify the name as a quoted
string.
The wrapper_name should be mysql, and may be quoted with
single quotes.
Other values for wrapper_name are not currently supported.
For each option you must specify either a character literal
or numeric literal.
Character literals are UTF-8, support a maximum length of 64
characters and
default to a blank (empty) string. String literals are
silently truncated to 64
characters. Numeric literals must be a number between 0 and
9999, default value
is 0.
Note: The OWNER option is currently not applied, and has no
effect on
the ownership or operation of the server connection that is
created.
The CREATE SERVER statement creates an entry in the
mysql.servers table that can later be used with the
CREATE TABLE statement when creating a Spider, FederatedX or
FEDERATED table. The options that you specify will
be used to populate the columns in the mysql.servers table.
The table columns
are Server_name, Host, Db, Username, Password, Port and
Socket.
DROP SERVER removes a previously created server definition.
CREATE SERVER is not written to the binary log, irrespective
of
the binary log format being used.
For valid identifiers to use as server names, see Identifier
Names.
OR REPLACE
If the optional OR REPLACE clause is used, it acts as a
shortcut for:
DROP SERVER IF EXISTS name;
CREATE SERVER server_name ...;
IF NOT EXISTS
If the IF NOT EXISTS clause is used, MariaDB will return a
warning instead of an error if the server already exists.
Cannot be used together with OR REPLACE.
Examples
--------
CREATE SERVER s
FOREIGN DATA WRAPPER mysql
OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE
'test');
OR REPLACE and IF NOT EXISTS:
CREATE SERVER s
FOREIGN DATA WRAPPER mysql
OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE
'test');
ERROR 1476 (HY000): The foreign server, s, you are trying to
create already exists
CREATE OR REPLACE SERVER s
FOREIGN DATA WRAPPER mysql
OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE
'test');
Query OK, 0 rows affected (0.00 sec)
CREATE SERVER IF NOT EXISTS s
FOREIGN DATA WRAPPER mysql
OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE
'test');
Query OK, 0 rows affected, 1 warning (0.00 sec)
SHOW WARNINGS;
+-------+------+----------------------------------------------------------------+
| Level | Code | Message |
+-------+------+----------------------------------------------------------------+
| Note | 1476 | The foreign server, s, you are trying to
create already exists |
+-------+------+----------------------------------------------------------------+
URL: https://mariadb.com/kb/en/create-server/https://mariadb.com/kb/en/create-server/ �
% ' DROP EVENTSyntax
------
DROP EVENT [IF EXISTS] event_name
Description
-----------
This statement drops the event named event_name. The event
immediately
ceases being active, and is deleted completely from the
server.
If the event does not exist, the error
ERROR 1517 (HY000): Unknown event 'event_name'
results. You can override this and cause the
statement to generate a NOTE for non-existent events instead
by using
IF EXISTS. See SHOW WARNINGS.
This statement requires the EVENT privilege. In MySQL 5.1.11
and earlier, an event could be dropped only
by its definer, or by a user having the SUPER privilege.
Examples
--------
DROP EVENT myevent3;
Using the IF EXISTS clause:
DROP EVENT IF EXISTS myevent3;
Query OK, 0 rows affected, 1 warning (0.01 sec)
SHOW WARNINGS;
+-------+------+-------------------------------+
| Level | Code | Message |
+-------+------+-------------------------------+
| Note | 1305 | Event myevent3 does not exist |
+-------+------+-------------------------------+
URL: https://mariadb.com/kb/en/drop-event/https://mariadb.com/kb/en/drop-event/ �
X( ' DROP FUNCTIONSyntax
------
DROP FUNCTION [IF EXISTS] f_name
Description
-----------
The DROP FUNCTION statement is used to drop a stored
function or a user-defined function (UDF). That is, the
specified routine is removed from the server, along with all
privileges specific to the function. You must have the ALTER
ROUTINE privilege for the routine in order to drop it. If
the automatic_sp_privileges server system variable is set,
both the ALTER ROUTINE and EXECUTE privileges are granted
automatically to the routine creator - see Stored Routine
Privileges.
IF EXISTS
The IF EXISTS clause is a MySQL/MariaDB extension. It
prevents an error from occurring if the function does not
exist. A
NOTE is produced that can be viewed with SHOW WARNINGS.
For dropping a user-defined functions (UDF), see DROP
FUNCTION UDF.
Examples
--------
DROP FUNCTION hello;
Query OK, 0 rows affected (0.042 sec)
DROP FUNCTION hello;
ERROR 1305 (42000): FUNCTION test.hello does not exist
DROP FUNCTION IF EXISTS hello;
Query OK, 0 rows affected, 1 warning (0.000 sec)
SHOW WARNINGS;
+-------+------+------------------------------------+
| Level | Code | Message |
+-------+------+------------------------------------+
| Note | 1305 | FUNCTION test.hello does not exist |
+-------+------+------------------------------------+
URL: https://mariadb.com/kb/en/drop-function/https://mariadb.com/kb/en/drop-function/ ��{W o%m�[ Syntax
------
CREATE [OR REPLACE] [TEMPORARY] TABLE [IF NOT EXISTS]
tbl_name
(create_definition,...) [table_options ]...
[partition_options]
CREATE [OR REPLACE] [TEMPORARY] TABLE [IF NOT EXISTS]
tbl_name
[(create_definition,...)] [table_options ]...
[partition_options]
select_statement
CREATE [OR REPLACE] [TEMPORARY] TABLE [IF NOT EXISTS]
tbl_name
{ LIKE old_table_name | (LIKE old_table_name) }
select_statement:
[IGNORE | REPLACE] [AS] SELECT ... (Some legal select
statement)
Description
-----------
Use the CREATE TABLE statement to create a table with the
given name.
In its most basic form, the CREATE TABLE statement provides
a table name
followed by a list of columns, indexes, and constraints. By
default, the table
is created in the default database. Specify a database with
db_name.tbl_name.
If you quote the table name, you must quote the database
name and table name
separately as `db_name`.`tbl_name`. This is particularly
useful for CREATE TABLE ... SELECT, because it allows to
create a table into a database, which contains data from
other databases. See Identifier Qualifiers.
If a table with the same name exists, error 1050 results.
Use IF NOT EXISTS
to suppress this error and issue a note instead. Use SHOW
WARNINGS
to see notes.
The CREATE TABLE statement automatically commits the current
transaction,
except when using the TEMPORARY keyword.
For valid identifiers to use as table names, see Identifier
Names.
Note: if the default_storage_engine is set to ColumnStore
then it needs setting on all UMs. Otherwise when the tables
using the default engine are replicated across UMs they will
use the wrong engine. You should therefore not use this
option as a session variable with ColumnStore.
Microsecond precision can be between 0-6. If no precision is
specified it is assumed to be 0, for backward compatibility
reasons.
Privileges
Executing the CREATE TABLE statement requires the CREATE
privilege for the table or the database.
CREATE OR REPLACE TABLE ...
The OR REPLACE clause was added in MariaDB 10.0.8.
If the OR REPLACE clause is used and if the table already
exists, then instead of returning an error, the server will
drop the existing table and replace it with the newly
defined table.
This syntax was originally added to make replication more
robust if it has to rollback and repeat statements such as
CREATE ... SELECT on slaves.
CREATE OR REPLACE TABLE table_name (a int);
is basically the same as:
DROP TABLE IF EXISTS table_name;
CREATE TABLE table_name (a int);
with the following exceptions:
If table_name was locked with LOCK TABLES it will continue
to be locked after the statement.
Temporary tables are only dropped if the TEMPORARY keyword
was used. (With DROP TABLE, temporary tables are preferred
to be dropped before normal tables).
Things to be Aware of With CREATE OR REPLACE
The table is dropped first (if it existed), after that the
CREATE is done. Because of this, if the CREATE fails, then
the table will not exist anymore after the statement. If the
table was used with LOCK TABLES it will be unlocked.
One can't use OR REPLACE together with IF EXISTS.
Slaves in replication will by default use CREATE OR REPLACE
when replicating CREATE statements that don''t use IF
EXISTS. This can be changed by setting the variable
slave-ddl-exec-mode to STRICT.
CREATE TABLE IF NOT EXISTS ...
If the IF NOT EXISTS clause is used, then the index will
only be created if an index with the same name does not
already exist. If the index already exists, then a warning
will be triggered by default.
CREATE TEMPORARY TABLE ...
Use the TEMPORARY keyword to create a temporary table that
is only available to your current session. Temporary tables
are dropped when the your session ends. Temporary table
names are specific to your session. They will not conflict
with other temporary tables from other session even if they
share the same name. They will shadow names of non-temporary
tables or views, if they are identical. A temporary table
can have the same name as a non-temporary table which is
located in the same database. In that case, their name will
reference the temporary table when used in SQL statements.
You must have the CREATE TEMPORARY TABLES privilege on the
database to create temporary tables. If no storage engine is
specified, the default_tmp_storage_engine setting will
determine the engine.
CREATE TABLE ... LIKE
Use the LIKE clause instead of a full table definition to
create a table with the same definition as another table,
including columns, indexes, and table options. Foreign key
definitions, as well as any DATA DIRECTORY or INDEX
DIRECTORY table options specified on the original table,
will not be created.
CREATE TABLE ... SELECT
You can create a table containing data from other tables
using the CREATE ... SELECT statement. Columns will be
created in the table for each field returned by the SELECT
query.
You can also define some columns normally and add other
columns from a SELECT. You can also create columns in the
normal way and assign them some values using the query, this
is done to force a certain type or other field
characteristics. The columns that are not named in the query
will be placed before the others. For example:
CREATE TABLE test (a INT NOT NULL, b CHAR(10)) ENGINE=MyISAM
SELECT 5 AS b, c, d FROM another_table;
Remember that the query just returns data. If you want to
use the same indexes, or the same columns attributes ([NOT]
NULL, DEFAULT, AUTO_INCREMENT) in the new table, you need to
specify them manually. Types and sizes are not automatically
preserved if no data returned by the SELECT requires the
full size, and VARCHAR could be converted into CHAR. The
CAST() function can be used to forcee the new table to use
certain types.
Aliases (AS) are taken into account, and they should always
be used when you SELECT an expression (function,
arithmetical operation, etc).
If an error occurs during the query, the table will not be
created at all.
If the new table has a primary key or UNIQUE indexes, you
can use the IGNORE or REPLACE keywords to handle duplicate
key errors during the query. IGNORE means that the newer
values must not be inserted an identical value exists in the
index. REPLACE means that older values must be overwritten.
If the columns in the new table are more than the rows
returned by the query, the columns populated by the query
will be placed after other columns. Note that if the strict
SQL_MODE is on, and the columns that are not names in the
query do not have a DEFAULT value, an error will raise and
no rows will be copied.
Concurrent inserts are not used during the execution of a
CREATE ... SELECT.
If the table already exists, an error similar to the
following will be returned:
ERROR 1050 (42S01): Table 't' already exists
If the IF NOT EXISTS clause is used and the table exists, a
note will be produced instead of an error.
To insert rows from a query into an existing table, INSERT
... SELECT can be used.
Column Definitions
create_definition:
{ col_name column_definition | index_definition |
period_definition | CHECK (expr) }
column_definition:
data_type
[NOT NULL | NULL] [DEFAULT default_value | (expression)]
[AUTO_INCREMENT] [ZEROFILL] [UNIQUE [KEY] | [PRIMARY] KEY]
[INVISIBLE] [{WITH|WITHOUT} SYSTEM VERSIONING]
[COMMENT 'string']
[COLUMN_FORMAT {FIXED|DYNAMIC|DEFAULT}]
[reference_definition]
| data_type [GENERATED ALWAYS]
AS { { ROW {START|END} } | { (expression) [VIRTUAL |
PERSISTENT | STORED] } }
[UNIQUE [KEY]] [COMMENT 'string']
constraint_definition:
CONSTRAINT [constraint_name] CHECK (expression)
Note: MariaDB accepts the REFERENCES clause in ALTER TABLE
and CREATE TABLE column definitions, but that syntax does
nothing. MariaDB simply parses it without returning any
error or warning, for compatibility with other DBMS's.
Before MariaDB 10.2.1 this was also true for CHECK
constraints. Only the syntax for indexes described below
creates foreign keys.
Each definition either creates a column in the table or
specifies and index or
constraint on one or more columns. See Indexes below for
details
on�U creating indexes.
Create a column by specifying a column name and a data type,
optionally
followed by column options. See Data Types for a full list
of data types allowed in MariaDB.
NULL and NOT NULL
Use the NULL or NOT NULL options to specify that values in
the column
may or may not be NULL, respectively. By default, values may
be NULL. See also NULL Values in MariaDB.
DEFAULT Column Option
The DEFAULT clause was enhanced in MariaDB 10.2.1. Some
enhancements include
BLOB and TEXT columns now support DEFAULT.
The DEFAULT clause can now be used with an expression or
function.
Specify a default value using the DEFAULT clause. If you
don't specify DEFAULT then the following rules apply:
If the column is not defined with NOT NULL, AUTO_INCREMENT
or TIMESTAMP, an explicit DEFAULT NULL will be added.
Note that in MySQL and in MariaDB before 10.1.6, you may get
an explicit DEFAULT for primary key parts, if not specified
with NOT NULL.
The default value will be used if you INSERT a row without
specifying a value for that column, or if you specify
DEFAULT for that column.
Before MariaDB 10.2.1 you couldn't usually provide an
expression or function to evaluate at
insertion time. You had to provide a constant default value
instead. The one
exception is that you may use CURRENT_TIMESTAMP as
the default value for a TIMESTAMP column to use the current
timestamp at insertion time.
CURRENT_TIMESTAMP may also be used as
the default value for a DATETIME
From MariaDB 10.2.1 you can use most functions in DEFAULT.
Expressions should have parentheses around them. If you use
a non deterministic function in DEFAULT then all inserts to
the table will be replicated in row mode. You can even refer
to earlier columns in the DEFAULT expression:
CREATE TABLE t1 (a int DEFAULT (1+1), b int DEFAULT (a+1));
CREATE TABLE t2 (a bigint primary key DEFAULT UUID_SHORT());
The DEFAULT clause cannot contain any stored functions or
subqueries, and a column used in the clause must already
have been defined earlier in the statement.
Since MariaDB 10.2.1, it is possible to assign BLOB or TEXT
columns a DEFAULT value. In earlier versions, assigning a
default to these columns was not possible.
Starting from 10.3.3 you can also use DEFAULT (NEXT VALUE
FOR sequence)
AUTO_INCREMENT Column Option
Use AUTO_INCREMENT to create a column whose value can
can be set automatically from a simple counter. You can only
use AUTO_INCREMENT
on a column with an integer type. The column must be a key,
and there can only be
one AUTO_INCREMENT column in a table. If you insert a row
without specifying
a value for that column (or if you specify 0, NULL, or
DEFAULT
as the value), the actual value will be taken from the
counter, with each insertion
incrementing the counter by one. You can still insert a
value explicitly. If you
insert a value that is greater than the current counter
value, the counter is
set based on the new value. An AUTO_INCREMENT column is
implicitly NOT NULL.
Use LAST_INSERT_ID to get the AUTO_INCREMENT value
most recently used by an INSERT statement.
ZEROFILL Column Option
If the ZEROFILL column option is specified for a column
using a numeric data type, then the column will be set to
UNSIGNED and the spaces used by default to pad the field are
replaced with zeros. ZEROFILL is ignored in expressions or
as part of a UNION. ZEROFILL is a non-standard MySQL and
MariaDB enhancement.
PRIMARY KEY Column Option
Use PRIMARY KEY (or just KEY) to make a column a primary
key. A primary key is a special type of a unique key. There
can be at most one primary key per table, and it is
implicitly NOT NULL.
Specifying a column as a unique key creates a unique index
on that column. See the Index Definitions section below for
more information.
UNIQUE KEY Column Option
Use UNIQUE KEY (or just UNIQUE) to specify that all values
in the column
must be distinct from each other. Unless the column is NOT
NULL, there may be
multiple rows with NULL in the column.
Specifying a column as a unique key creates a unique index
on that column. See the Index Definitions section below for
more information.
COMMENT Column Option
You can provide a comment for each column using the COMMENT
clause. The maximum length is 1024 characters (it was 255
characters before MariaDB 5.5). Use
the SHOW FULL COLUMNS statement to see column comments.
Generated Columns
A generated column is a column in a table that cannot
explicitly be set to a specific value in a DML query.
Instead, its value is automatically generated based on an
expression. This expression might generate the value based
on the values of other columns in the table, or it might
generate the value by calling built-in functions or
user-defined functions (UDFs).
There are two types of generated columns:
PERSISTENT or STORED: This type's value is actually stored
in the table.
VIRTUAL: This type's value is not stored at all. Instead,
the value is generated dynamically when the table is
queried. This type is the default.
Generated columns are also sometimes called computed columns
or virtual columns.
For a complete description about generated columns and their
limitations, see Generated (Virtual and Persistent/Stored)
Columns.
COLUMN_FORMAT
COLUMN_FORMAT is only used by MySQL Cluster, and is silently
ignored in MariaDB.
COMPRESSED
Certain columns may be compressed. See Storage-Engine
Independent Column Compression.
INVISIBLE
Columns may be made invisible, and hidden in certain
contexts. See Invisible Columns.
WITH SYSTEM VERSIONING Column Option
Columns may be explicitly marked as included from system
versioning. See System-versioned tables for details.
WITHOUT SYSTEM VERSIONING Column Option
Columns may be explicitly marked as excluded from system
versioning. See System-versioned tables for details.
Index Definitions
index_definition:
{INDEX|KEY} [index_name] [index_type] (index_col_name,...)
[index_option] ...
| {FULLTEXT|SPATIAL} [INDEX|KEY] [index_name]
(index_col_name,...) [index_option] ...
| [CONSTRAINT [symbol]] PRIMARY KEY [index_type]
(index_col_name,...) [index_option] ...
| [CONSTRAINT [symbol]] UNIQUE [INDEX|KEY] [index_name]
[index_type] (index_col_name,...) [index_option] ...
| [CONSTRAINT [symbol]] FOREIGN KEY [index_name]
(index_col_name,...) reference_definition
index_col_name:
col_name [(length)] [ASC | DESC]
index_type:
USING {BTREE | HASH | RTREE}
index_option:
KEY_BLOCK_SIZE [=] value
| index_type
| WITH PARSER parser_name
| COMMENT 'string'
| CLUSTERING={YES| NO}
reference_definition:
REFERENCES tbl_name (index_col_name,...)
[MATCH FULL | MATCH PARTIAL | MATCH SIMPLE]
[ON DELETE reference_option]
[ON UPDATE reference_option]
reference_option:
RESTRICT | CASCADE | SET NULL | NO ACTION
INDEX and KEY are synonyms.
Index names are optional, if not specified an automatic name
will be assigned. Index name are needed to drop indexes and
appear in error messages when a constraint is violated.
Index Categories
Plain Indexes
Plain indexes are regular indexes that are not unique, and
are not acting as a primary key or a foreign key. They are
also not the "specialized" FULLTEXT or SPATIAL indexes.
See Getting Started with Indexes: Plain Indexes for more
information.
PRIMARY KEY
For PRIMARY KEY indexes, you can specify a name for the
index, but it is silently ignored, and the name of the index
is always PRIMARY.
See Getting Started with Indexes: Primary Key for more
information.
UNIQUE
The UNIQUE keyword means that the index will not accept
duplicated values, except for NULLs. An error will raise if
you try to insert duplicate values in a UNIQUE index.
For UNIQUE indexes, you can specify a name for the
constraint, using the CONSTRAINT keyword. That name will be
used in error messages.
See Getting Started with Indexes: Unique Index for more
information.
FOREIGN KEY
For FOREIGN KEY indexes, a reference definition must be
provided.
For FOREIGN KEY indexes, you can specify a name for the
constraint, using the CONSTRAINT keyword. That name will be
used in error messages.
First, you have to specify the name of the ta��a� rget (parent)
table and a column or a column list which must be indexed
and whose values must match to the foreign key's values.
The MATCH clause is accepted to improve the compatibility
with other DBMS's, but has no meaning in MariaDB. The ON
DELETE and ON UPDATE clauses specify what must be done when
a DELETE (or a REPLACE) statements attempts to delete a
referenced row from the parent table, and when an UPDATE
statement attempts to modify the referenced foreign key
columns in a parent table row, respectively. The following
options are allowed:
RESTRICT: The delete/update operation is not performed. The
statement terminates with a 1451 error (SQLSTATE '2300').
NO ACTION: Synonym for RESTRICT.
CASCADE: The delete/update operation is performed in both
tables.
SET NULL: The update or delete goes ahead in the parent
table, and the corresponding foreign key fields in the child
table are set to NULL. (They must not be defined as NOT NULL
for this to succeed).
SET DEFAULT: This option is currently implemented only for
the PBXT storage engine, which is disabled by default and no
longer maintained. It sets the child table's foreign key
fields to their DEFAULT values when the referenced parent
table key entries are updated or deleted.
If either clause is omitted, the default behavior for the
omitted clause is RESTRICT.
See Foreign Keys for more information.
FULLTEXT
Use the FULLTEXT keyword to create full-text indexes.
See Full-Text Indexes for more information.
SPATIAL
Use the SPATIAL keyword to create geometric indexes.
See SPATIAL INDEX for more information.
Index Options
KEY_BLOCK_SIZE Index Option
The KEY_BLOCK_SIZE index option is similar to the
KEY_BLOCK_SIZE table option.
With the InnoDB storage engine, if you specify a non-zero
value for the KEY_BLOCK_SIZE table option for the whole
table, then the table will implicitly be created with the
ROW_FORMAT table option set to COMPRESSED. However, this
does not happen if you just set the KEY_BLOCK_SIZE index
option for one or more indexes in the table. The InnoDB
storage engine ignores the KEY_BLOCK_SIZE index option.
However, the SHOW CREATE TABLE statement may still report it
for the index.
For information about the KEY_BLOCK_SIZE index option, see
the KEY_BLOCK_SIZE table option below.
Index Types
Each storage engine supports some or all index types. See
Storage Engine Index Types for details on permitted index
types for each storage engine.
Different index types are optimized for different kind of
operations:
BTREE is the default type, and normally is the best choice.
It is supported by all storage engines. It can be used to
compare a column's value with a value using the =, >, >=,
0) ,b int check (b> 0), constraint abc check (a>b));
If you use the second format and you don't give a name to
the constraint, then the constraint will get a auto
generated name. This is done so that you can later delete
the constraint with ALTER TABLE DROP constraint_name.
One can disable all constraint expression checks by setting
the variable check_constraint_checks to OFF. This is useful
for example when loading a table that violates some
constraints that you want to later find and fix in SQL.
See CONSTRAINT for more information.
Table Options
For each individual table you create (or alter), you can set
some table options. The general syntax for setting options
is:
= , [ = ...]
The equal sign is optional.
Some options are supported by the server and can be used for
all tables, no matter what storage engine they use; other
options can be specified for all storage engines, but have a
meaning only for some engines. Also, engines can extend
CREATE TABLE with new options.
If the IGNORE_BAD_TABLE_OPTIONS SQL_MODE is enabled, wrong
table options generate a warning; otherwise, they generate
an error.
table_option:
[STORAGE] ENGINE [=] engine_name
| AUTO_INCREMENT [=] value
| AVG_ROW_LENGTH [=] value
| [DEFAULT] CHARACTER SET [=] charset_name
| CHECKSUM [=] {0 | 1}
| [DEFAULT] COLLATE [=] collation_name
| COMMENT [=] 'string'
| CONNECTION [=] 'connect_string'
| DATA DIRECTORY [=] 'absolute path to directory'
| DELAY_KEY_WRITE [=] {0 | 1}
| ENCRYPTED [=] {YES | NO}
| ENCRYPTION_KEY_ID [=] value
| IETF_QUOTES [=] {YES | NO}
| INDEX DIRECTORY [=] 'absolute path to directory'
| INSERT_METHOD [=] { NO | FIRST | LAST }
| KEY_BLOCK_SIZE [=] value
| MAX_ROWS [=] value
| MIN_ROWS [=] value
| PACK_KEYS [=] {0 | 1 | DEFAULT}
| PAGE_CHECKSUM [=] {0 | 1}
| PAGE_COMPRESSED [=] {0 | 1}
| PAGE_COMPRESSION_LEVEL [=] {0 .. 9}
| PASSWORD [=] 'string'
| ROW_FORMAT [=]
{DEFAULT|DYNAMIC|FIXED|COMPRESSED|REDUNDANT|COMPACT|PAGE}
| SEQUENCE [=] {0|1}
| STATS_AUTO_RECALC [=] {DEFAULT|0|1}
| STATS_PERSISTENT [=] {DEFAULT|0|1}
| STATS_SAMPLE_PAGES [=] {DEFAULT|value}
| TABLESPACE tablespace_name
| TRANSACTIONAL [=] {0 | 1}
| UNION [=] (tbl_name[,tbl_name]...)
| WITH SYSTEM VERSIONING
[STORAGE] ENGINE
[STORAGE] ENGINE specifies a storage engine for the table.
If this option is not used, the default storage engine is
used instead. That is, the storage_engine session option
value if it is set, or the value specified for the
--default-storage-engine mysqld startup options, or InnoDB.
If the specified storage engine is not installed and active,
the default value will be used, unless the
NO_ENGINE_SUBSTITUTION SQL MODE is set (default since
MariaDB 10.0). This is only true for CREATE TABLE, not for
ALTER TABLE. For a list of storage engines that are present
in your server, issue a SHOW ENGINES.
AUTO_INCREMENT
AUTO_INCREMENT specifies the initial value for the
AUTO_INCREMENT primary key. This works for MyISAM, Aria,
InnoDB/XtraDB, MEMORY, and ARCHIVE tables. You can change
this option with ALTER TABLE, but in that case the new value
must be higher than the highest value which is present in
the AUTO_INCREMENT column. If the storage engine does not
support this option, you can insert (and then delete) a row
having the wanted value - 1 in the AUTO_INCREMENT column.
AVG_ROW_LENGTH
AVG_ROW_LENGTH is the average rows size. It only applies to
tables using MyISAM and Aria storage engines that have the
ROW_FORMAT table option set to FIXED format.
MyISAM uses MAX_ROWS and AVG_ROW_LENGTH to decide the
maximum size of a table (default: 256TB, or the maximum file
size allowed by the system).
[DEFAULT] CHARACTER SET/CHARSET
[DEFAULT] CHARACTER SET (or [DEFAULT] CHARSET) is used to
set a default character set for the table. This is the
character set used for all columns where an explicit
character set is not specified. If this option is omitted or
DEFAULT is specified, database's default character set will
be used. See Setting Character Sets and Collations for
details on setting the character sets.
CHECKSUM/TABLE_CHECKSUM
CHECKSUM (or TABLE_CHECKSUM) can be set to 1 to maintain a
live checksum for all table's rows. This makes write
operations slower, but CHECKSUM TABLE will be very fast.
This option is only supported for MyISAM and Aria tables.
[DEFAULT] COLLATE
[DEFAULT] COLLATE is used to set a default collation for the
table. This is the collation used for all columns where an
explicit character set is not specified. If this option is
omitted or DEFAULT is specified, database's default option
will be used. See Setting Character Sets and Collations for
details on setting the collations
COMMENT
COMMENT is a comment for the table. Maximum length is 2048
characters (before mariaDB 5.5 it was 60 characters). Also
used to define table parameters when creating a Spider
table.
CONNECTION
CONNECTION is used to specify a server name or a connection
string for a Spider, CONNECT, Federated or FederatedX table.
DATA DIRECTORY/INDEX DIRECTORY
DATA DIRECTORY and INDEX DIRECTORY were only supported for
MyISAM and Aria, before MariaDB 5.5. Since 5.5, DATA
DIRECTORY has also been supported by InnoDB if the
innodb_file_per_table server system variable is enabled, but
only in CREATE TABLE, not in ALTER TABLE. So, carefully
choose a path for InnoDB tables at creation time, because it
cannot be changed without dropping and re-creating the
table. Th�n�� ese options specify the paths for data files and
index files, respectively. If these options are omitted, the
database's directory will be used to store data files and
index files. Note that these table options do not work for
partitioned tables (use the partition options instead), or
if the server has been invoked with the
--skip-symbolic-links startup option. To avoid the
overwriting of old files with the same name that could be
present in the directories, you can use the
--keep_files_on_create option (an error will be issued if
files already exist). These options are ignored if the
NO_DIR_IN_CREATE SQL_MODE is enabled (useful for replication
slaves). Also note that symbolic links cannot be used for
InnoDB tables.
DATA DIRECTORY works by creating symlinks from where the
table would normally have been (inside the datadir) to where
the option specifies. For security reasons, to avoid
bypassing the privilege system, the server does not permit
symlinks inside the datadir. Therefore, DATA DIRECTORY
cannot be used to specify a location inside the datadir. An
attempt to do so will result in an error 1210 (HY000)
Incorrect arguments to DATA DIRECTORY.
DELAY_KEY_WRITE
DELAY_KEY_WRITE is supported by MyISAM and Aria, and can be
set to 1 to speed up write operations. In that case, when
data are modified, the indexes are not updated until the
table is closed. Writing the changes to the index file
altogether can be much faster. However, note that this
option is applied only if the delay_key_write server
variable is set to 'ON'. If it is 'OFF' the delayed
index writes are always disabled, and if it is 'ALL' the
delayed index writes are always used, disregarding the value
of DELAY_KEY_WRITE.
ENCRYPTED
The ENCRYPTED table option was added in MariaDB 10.1.4
The ENCRYPTED table option can be used to manually set the
encryption status of an InnoDB table. See InnoDB / XtraDB
Encryption for more information.
Aria does not currently support the ENCRYPTED table option.
See MDEV-18049 about that.
See Data-at-Rest Encryption for more information.
ENCRYPTION_KEY_ID
The ENCRYPTION_KEY_ID table option was added in MariaDB
10.1.4
The ENCRYPTION_KEY_ID table option can be used to manually
set the encryption key of an InnoDB table. See InnoDB /
XtraDB Encryption for more information.
Aria does not currently support the ENCRYPTION_KEY_ID table
option. See MDEV-18049 about that.
See Data-at-Rest Encryption for more information.
IETF_QUOTES
The IETF_QUOTES option was added in MariaDB 10.1.8
For the CSV storage engine, the IETF_QUOTES option, when set
to YES, enables IETF-compatible parsing of embedded quote
and comma characters. Enabling this option for a table
improves compatibility with other tools that use CSV, but is
not compatible with MySQL CSV tables, or MariaDB CSV tables
created without this option. Disabled by default.
INSERT_METHOD
INSERT_METHOD is only used with MERGE tables. This option
determines in which underlying table the new rows should be
inserted. If you set it to 'NO' (which is the default) no
new rows can be added to the table (but you will still be
able to perform INSERTs directly against the underlying
tables). FIRST means that the rows are inserted into the
first table, and LAST means that thet are inserted into the
last table.
KEY_BLOCK_SIZE
KEY_BLOCK_SIZE is used to determine the size of key blocks,
in bytes or kilobytes. However, this value is just a hint,
and the storage engine could modify or ignore it. If
KEY_BLOCK_SIZE is set to 0, the storage engine's default
value will be used.
With the InnoDB storage engine, if you specify a non-zero
value for the KEY_BLOCK_SIZE table option for the whole
table, then the table will implicitly be created with the
ROW_FORMAT table option set to COMPRESSED.
MIN_ROWS/MAX_ROWS
MIN_ROWS and MAX_ROWS let the storage engine know how many
rows you are planning to store as a minimum and as a
maximum. These values will not be used as real limits, but
they help the storage engine to optimize the table. MIN_ROWS
is only used by MEMORY storage engine to decide the minimum
memory that is always allocated. MAX_ROWS is used to decide
the minimum size for indexes.
PACK_KEYS
PACK_KEYS can be used to determine whether the indexes will
be compressed. Set it to 1 to compress all keys. With a
value of 0, compression will not be used. With the DEFAULT
value, only long strings will be compressed. Uncompressed
keys are faster.
PAGE_CHECKSUM
PAGE_CHECKSUM is only applicable to Aria tables, and
determines whether indexes and data should use page
checksums for extra safety.
PAGE_COMPRESSED
PAGE_COMPRESSED is used to enable InnoDB page compression
for InnoDB tables.
PAGE_COMPRESSION_LEVEL
PAGE_COMPRESSION_LEVEL is used to set the compression level
for InnoDB page compression for InnoDB tables. The table
must also have the PAGE_COMPRESSED table option set to 1.
Valid values for PAGE_COMPRESSION_LEVEL are 1 (the best
speed) through 9 (the best compression), .
PASSWORD
PASSWORD is unused.
RAID_TYPE
RAID_TYPE is an obsolete option, as the raid support has
been disabled since MySQL 5.0.
ROW_FORMAT
The ROW_FORMAT table option specifies the row format for the
data file. Possible values are engine-dependent.
Supported MyISAM Row Formats
For MyISAM, the supported row formats are:
FIXED
DYNAMIC
COMPRESSED
The COMPRESSED row format can only be set by the myisampack
command line tool.
See MyISAM Storage Formats for more information.
Supported Aria Row Formats
For Aria, the supported row formats are:
PAGE
FIXED
DYNAMIC.
See Aria Storage Formats for more information.
Supported InnoDB Row Formats
For InnoDB/XtraDB, the supported row formats are:
COMPACT
REDUNDANT
COMPRESSED
DYNAMIC.
If the ROW_FORMAT table option is set to FIXED for an InnoDB
table, then the server will either return an error or a
warning depending on the value of the innodb_strict_mode
system variable. If the innodb_strict_mode system variable
is set to OFF, then a warning is issued, and MariaDB will
create the table using the default row format for the
specific MariaDB server version. If the innodb_strict_mode
system variable is set to ON, then an error will be raised.
See XtraDB/InnoDB Storage Formats for more information.
Other Storage Engines and ROW_FORMAT
Other storage engines do not support the ROW_FORMAT table
option.
SEQUENCE
If the table is a sequence, then it will have the SEQUENCE
set to 1.
STATS_AUTO_RECALC
STATS_AUTO_RECALC is available only in MariaDB 10.0+. It
indicates whether to automatically recalculate persistent
statistics (see STATS_PERSISTENT, below) for an InnoDB
table.
If set to 1, statistics will be recalculated when more than
10% of the data has changed. When set to 0, stats will be
recalculated only when an ANALYZE TABLE is run. If set to
DEFAULT, or left out, the value set by the
innodb_stats_auto_recalc system variable applies. See InnoDB
Persistent Statistics.
STATS_PERSISTENT
STATS_PERSISTENT is available only in MariaDB 10.0+. It
indicates whether the InnoDB statistics created by ANALYZE
TABLE will remain on disk or not. It can be set to 1 (on
disk), 0 (not on disk, the pre-MariaDB 10 behavior), or
DEFAULT (the same as leaving out the option), in which case
the value set by the innodb_stats_persistent system variable
will apply. Persistent statistics stored on disk allow the
statistics to survive server restarts, and provide better
query plan stability. See InnoDB Persistent Statistics.
STATS_SAMPLE_PAGES
STATS_SAMPLE_PAGES is available only in MariaDB 10.0+. It
indicates how many pages are used to sample index
statistics. If 0 or DEFAULT, the default value, the
innodb_stats_sample_pages value is used. See InnoDB
Persistent Statistics.
TRANSACTIONAL
TRANSACTIONAL is only applicable for Aria tables. In future
Aria tables created with this option will be fully
transactional, but currently this provides a form of crash
protection. See Aria Storage Engine for more details.
UNION
UNION must be specified when you create a MERGE table. This
option contains a comma-separated list of MyISAM tables
which are accesse��& ��d by the new table. The list is enclosed
between parenthesis. Example: UNION = (t1,t2)
WITH SYSTEM VERSIONING
WITH SYSTEM VERSIONING is used for creating System-versioned
tables.
Partitions
partition_options:
PARTITION BY
{ [LINEAR] HASH(expr)
| [LINEAR] KEY(column_list)
| RANGE(expr)
| LIST(expr)
| SYSTEM_TIME [INTERVAL time_quantity time_unit] [LIMIT
num] }
[PARTITIONS num]
[SUBPARTITION BY
{ [LINEAR] HASH(expr)
| [LINEAR] KEY(column_list) }
[SUBPARTITIONS num]
]
[(partition_definition [, partition_definition] ...)]
partition_definition:
PARTITION partition_name
[VALUES {LESS THAN {(expr) | MAXVALUE} | IN (value_list)}]
[[STORAGE] ENGINE [=] engine_name]
[COMMENT [=] 'comment_text' ]
[DATA DIRECTORY [=] 'data_dir']
[INDEX DIRECTORY [=] 'index_dir']
[MAX_ROWS [=] max_number_of_rows]
[MIN_ROWS [=] min_number_of_rows]
[TABLESPACE [=] tablespace_name]
[NODEGROUP [=] node_group_id]
[(subpartition_definition [, subpartition_definition] ...)]
subpartition_definition:
SUBPARTITION logical_name
[[STORAGE] ENGINE [=] engine_name]
[COMMENT [=] 'comment_text' ]
[DATA DIRECTORY [=] 'data_dir']
[INDEX DIRECTORY [=] 'index_dir']
[MAX_ROWS [=] max_number_of_rows]
[MIN_ROWS [=] min_number_of_rows]
[TABLESPACE [=] tablespace_name]
[NODEGROUP [=] node_group_id]
If the PARTITION BY clause is used, the table will be
partitioned. A partition method must be explicitly indicated
for partitions and subpartitions. Partition methods are:
[LINEAR] HASH creates a hash key which will be used to read
and write rows. The partition function can be any valid SQL
expression which returns an INTEGER number. Thus, it is
possible to use the HASH method on an integer column, or on
functions which accept integer columns as an argument.
However, VALUES LESS THAN and VALUES IN clauses can not be
used with HASH. An example:
CREATE TABLE t1 (a INT, b CHAR(5), c DATETIME)
PARTITION BY HASH ( YEAR(c) );
[LINEAR] HASH can be used for subpartitions, too.
[LINEAR] KEY is similar to HASH, but the index has an even
distribution of data. Also, the expression can only be a
column or a list of columns. VALUES LESS THAN and VALUES IN
clauses can not be used with KEY.
RANGE partitions the rows using on a range of values, using
the VALUES LESS THAN operator. VALUES IN is not allowed with
RANGE. The partition function can be any valid SQL
expression which returns a single value.
LIST assignes partitions based on a table's column with a
restricted set of possible values. It is similar to RANGE,
but VALUES IN must be used for at least 1 columns, and
VALUES LESS THAN is disallowed.
SYSTEM_TIME partitioning is used for System-versioned tables
to store historical data separately from current data.
Only HASH and KEY can be used for subpartitions, and they
can be [LINEAR].
It is possible to define up to 1024 partitions and
subpartitions.
The number of defined partitions can be optionally specified
as PARTITION count. This can be done to avoid specifying all
partitions individually. But you can also declare each
individual partition and, additionally, specify a PARTITIONS
count clause; in the case, the number of PARTITIONs must
equal count.
Also see Partitioning Types Overview.
Sequences
CREATE TABLE can also be used to create a SEQUENCE. See
CREATE SEQUENCE and Sequence Overview.
Examples
--------
create table if not exists test (
a bigint auto_increment primary key,
name varchar(128) charset utf8,
key name (name(32))
) engine=InnoDB default charset latin1;
This example shows a couple of things:
Usage of IF NOT EXISTS; If the table already existed, it
will not be created. There will not be any error for the
client, just a warning.
How to create a PRIMARY KEY that is automatically generated.
How to specify a table-specific character set and another
for a column.
How to create an index (name) that is only partly indexed
(to save space).
The following clauses will work from MariaDB 10.2.1 only.
CREATE TABLE t1(
a int DEFAULT (1+1),
b int DEFAULT (a+1),
expires DATETIME DEFAULT(NOW() + INTERVAL 1 YEAR),
x BLOB DEFAULT USER()
);
URL: https://mariadb.com/kb/en/create-table/ A��R �l � ) ' CREATE TRIGGERSyntax
------
CREATE [OR REPLACE]
[DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
TRIGGER [IF NOT EXISTS] trigger_name trigger_time
trigger_event
ON tbl_name FOR EACH ROW
[{ FOLLOWS | PRECEDES } other_trigger_name ]
trigger_stmt
Description
-----------
This statement creates a new trigger. A trigger is a named
database
object that is associated with a table, and that activates
when a
particular event occurs for the table. The trigger becomes
associated
with the table named tbl_name, which must refer to a
permanent table.
You cannot associate a trigger with a TEMPORARY table or a
view.
CREATE TRIGGER requires the TRIGGER privilege for the table
associated
with the trigger. (Before MySQL 5.1.6, this statement
requires the
SUPER privilege.)
You can have multiple triggers for the same trigger_time and
trigger_event.
For valid identifiers to use as trigger names, see
Identifier Names.
OR REPLACE
If used and the trigger already exists, instead of an error
being returned, the existing trigger will be dropped and
replaced by the newly defined trigger.
DEFINER
The DEFINER clause determines the security context to be
used when
checking access privileges at trigger activation time.
IF NOT EXISTS
If the IF NOT EXISTS clause is used, the trigger will only
be created if a trigger of the same name does not exist. If
the trigger already exists, by default a warning will be
returned.
trigger_time
trigger_time is the trigger action time. It can be BEFORE or
AFTER to
indicate that the trigger activates before or after each row
to be
modified.
trigger_event
trigger_event indicates the kind of statement that activates
the
trigger. The trigger_event can be one of the following:
INSERT: The trigger is activated whenever a new row is
inserted into the table; for example, through INSERT, LOAD
DATA, and REPLACE statements.
UPDATE: The trigger is activated whenever a row is modified;
for example, through UPDATE statements.
DELETE: The trigger is activated whenever a row is deleted
from the table; for example, through DELETE and REPLACE
statements. However, DROP TABLE and TRUNCATE statements on
the table do not activate this trigger, because they do not
use DELETE. Dropping a partition does not activate DELETE
triggers, either.
FOLLOWS/PRECEDES other_trigger_name
The FOLLOWS other_trigger_name and PRECEDES
other_trigger_name options were added in MariaDB 10.2.3 as
part of supporting multiple triggers per action time.
This is the same syntax used by MySQL 5.7, although MySQL
5.7 does not have multi-trigger support.
FOLLOWS adds the new trigger after another trigger while
PRECEDES adds the new trigger before another trigger. If
neither option is used, the new trigger is added last for
the given action and time.
FOLLOWS and PRECEDES are not stored in the trigger
definition. However the trigger order is guaranteed to not
change over time. mysqldump and other backup methods will
not change trigger order.
You can verify the trigger order from the ACTION_ORDER
column in INFORMATION_SCHEMA.TRIGGERS table.
SELECT trigger_name, action_order FROM
information_schema.triggers
WHERE event_object_table='t1';
Examples
--------
CREATE DEFINER=`root`@`localhost` TRIGGER increment_animal
AFTER INSERT ON animals FOR EACH ROW
UPDATE animal_count SET animal_count.animals =
animal_count.animals+1;
OR REPLACE and IF NOT EXISTS
CREATE DEFINER=`root`@`localhost` TRIGGER increment_animal
AFTER INSERT ON animals FOR EACH ROW
UPDATE animal_count SET animal_count.animals =
animal_count.animals+1;
ERROR 1359 (HY000): Trigger already exists
CREATE OR REPLACE DEFINER=`root`@`localhost` TRIGGER
increment_animal
AFTER INSERT ON animals FOR EACH ROW
UPDATE animal_count SET animal_count.animals =
animal_count.animals+1;
Query OK, 0 rows affected (0.12 sec)
CREATE DEFINER=`root`@`localhost` TRIGGER IF NOT EXISTS
increment_animal
AFTER INSERT ON animals FOR EACH ROW
UPDATE animal_count SET animal_count.animals =
animal_count.animals+1;
Query OK, 0 rows affected, 1 warning (0.00 sec)
SHOW WARNINGS;
+-------+------+------------------------+
| Level | Code | Message |
+-------+------+------------------------+
| Note | 1359 | Trigger already exists |
+-------+------+------------------------+
1 row in set (0.00 sec)
URL: https://mariadb.com/kb/en/create-trigger/https://mariadb.com/kb/en/create-trigger/ �
�% ' DROP INDEXSyntax
------
DROP INDEX [IF EXISTS] index_name ON tbl_name
[WAIT n |NOWAIT]
[algorithm_option | lock_option] ...
algorithm_option:
ALGORITHM [=] {DEFAULT|INPLACE|COPY|NOCOPY|INSTANT}
lock_option:
LOCK [=] {DEFAULT|NONE|SHARED|EXCLUSIVE}
Description
-----------
DROP INDEX drops the index named index_name from the table
tbl_name.
This statement is mapped to an ALTER TABLE statement to drop
the
index.
If another connection is using the table, a metadata lock is
active, and this statement will wait until the lock is
released. This is also true for non-transactional tables.
See ALTER TABLE.
Another shortcut, CREATE INDEX, allows the creation of an
index.
To remove the primary key, `PRIMARY` must be specified as
index_name. Note that the quotes are necessary, because
PRIMARY is a keyword.
Privileges
Executing the DROP INDEX statement requires the INDEX
privilege for the table or the database.
Online DDL
In MariaDB 10.0 and later, online DDL is supported with the
ALGORITHM and LOCK clauses.
See InnoDB Online DDL Overview for more information on
online DDL with InnoDB.
DROP INDEX IF EXISTS ...
The IF EXISTS clause was added in MariaDB 10.1.4.
If the IF EXISTS clause is used, then MariaDB will return a
warning instead of an error if the index does not exist.
WAIT/NOWAIT
Set the lock wait timeout. See WAIT and NOWAIT.
ALGORITHM
See ALTER TABLE: ALGORITHM for more information.
LOCK
See ALTER TABLE: LOCK for more information.
Progress Reporting
MariaDB provides progress reporting for DROP INDEX statement
for clients
that support the new progress reporting protocol. For
example, if you were using the mysql client, then the
progress report might look like this::
URL: https://mariadb.com/kb/en/drop-index/https://mariadb.com/kb/en/drop-index/ Z. N�x�> Syntax
------
CREATE
[OR REPLACE]
[ALGORITHM = {UNDEFINED | MERGE | TEMPTABLE}]
[DEFINER = { user | CURRENT_USER | role | CURRENT_ROLE }]
[SQL SECURITY { DEFINER | INVOKER }]
VIEW [IF NOT EXISTS] view_name [(column_list)]
AS select_statement
[WITH [CASCADED | LOCAL] CHECK OPTION]
Description
-----------
The CREATE VIEW statement creates a new view, or replaces an
existing
one if the OR REPLACE clause is given. If the view does not
exist, CREATE OR
REPLACE VIEW is the same as CREATE VIEW. If the view does
exist, CREATE OR
REPLACE VIEW is the same as ALTER VIEW.
The select_statement is a SELECT statement that provides the
definition of
the view. (When you select from the view, you select in
effect using the SELECT
statement.) select_statement can select from base tables or
other views.
The view definition is "frozen" at creation time, so
changes to the underlying
tables afterwards do not affect the view definition. For
example, if a view is
defined as SELECT * on a table, new columns added to the
table later do not
become part of the view. A SHOW CREATE VIEW shows that
such queries are rewritten and column names are included in
the view
definition.
The view definition must be a query that does not return
errors at view
creation times. However, the base tables used by the views
might be altered
later and the query may not be valid anymore. In this case,
querying the view
will result in an error. CHECK TABLE helps in finding this
kind
of problems.
The ALGORITHM clause affects how MariaDB processes the
view. The DEFINER and SQL SECURITY clauses specify the
security context to be
used when checking access privileges at view invocation
time. The WITH CHECK
OPTION clause can be given to constrain inserts or updates
to rows in tables
referenced by the view. These clauses are described later in
this section.
The CREATE VIEW statement requires the CREATE VIEW privilege
for the
view, and some privilege for each column selected by the
SELECT
statement. For columns used elsewhere in the SELECT
statement you must
have the SELECT privilege. If the OR REPLACE clause is
present, you
must also have the DROP privilege for the view.
A view belongs to a database. By default, a new view is
created in the
default database. To create the view explicitly in a given
database,
specify the name as db_name.view_name when you create it.
CREATE VIEW test.v AS SELECT * FROM t;
Base tables and views share the same namespace within a
database, so a
database cannot contain a base table and a view that have
the same
name.
Views must have unique column names with no duplicates, just
like base
tables. By default, the names of the columns retrieved by
the SELECT
statement are used for the view column names. To define
explicit names
for the view columns, the optional column_list clause can be
given as
a list of comma-separated identifiers. The number of names
in
column_list must be the same as the number of columns
retrieved by the
SELECT statement.
MySQL until 5.1.28
Prior to MySQL 5.1.29, When you modify an existing view, the
current view definition is backed up and saved. It is stored
in that
table's database directory, in a subdirectory named arc.
The backup
file for a view v is named v.frm-00001. If you alter the
view again,
the next backup is named v.frm-00002. The three latest view
backup
definitions are stored. Backed up view definitions are not
preserved
by mysqldump, or any other such programs, but you can retain
them
using a file copy operation. However, they are not needed
for anything
but to provide you with a backup of your previous view
definition. It
is safe to remove these backup definitions, but only while
mysqld is
not running. If you delete the arc subdirectory or its files
while
mysqld is running, you will receive an error the next time
you try to
alter the view:
MariaDB [test]> ALTER VIEW v AS SELECT * FROM t;
ERROR 6 (HY000): Error on delete of
'.\test\arc/v.frm-0004' (Errcode: 2)
Columns retrieved by the SELECT statement can be simple
references to
table columns. They can also be expressions that use
functions,
constant values, operators, and so forth.
Unqualified table or view names in the SELECT statement are
interpreted with respect to the default database. A view can
refer to
tables or views in other databases by qualifying the table
or view
name with the proper database name.
A view can be created from many kinds of SELECT statements.
It can
refer to base tables or other views. It can use joins,
UNION, and
subqueries. The SELECT need not even refer to any tables.
The
following example defines a view that selects two columns
from another
table, as well as an expression calculated from those
columns:
CREATE TABLE t (qty INT, price INT);
INSERT INTO t VALUES(3, 50);
CREATE VIEW v AS SELECT qty, price, qty*price AS value FROM
t;
SELECT * FROM v;
+------+-------+-------+
| qty | price | value |
+------+-------+-------+
| 3 | 50 | 150 |
+------+-------+-------+
A view definition is subject to the following restrictions:
The SELECT statement cannot contain a subquery in the FROM
clause.
The SELECT statement cannot refer to system or user
variables.
Within a stored program, the definition cannot refer to
program parameters or local variables.
The SELECT statement cannot refer to prepared statement
parameters.
Any table or view referred to in the definition must exist.
However, after a view has been created, it is possible to
drop a table or view that the definition refers to. In this
case, use of the view results in an error. To check a view
definition for problems of this kind, use the CHECK TABLE
statement.
The definition cannot refer to a TEMPORARY table, and you
cannot create a TEMPORARY view.
Any tables named in the view definition must exist at
definition time.
You cannot associate a trigger with a view.
For valid identifiers to use as view names, see Identifier
Names.
ORDER BY is allowed in a view definition, but it is ignored
if you
select from a view using a statement that has its own ORDER
BY.
For other options or clauses in the definition, they are
added to the
options or clauses of the statement that references the
view, but the
effect is undefined. For example, if a view definition
includes a
LIMIT clause, and you select from the view using a statement
that has
its own LIMIT clause, it is undefined which limit applies.
This same
principle applies to options such as ALL, DISTINCT, or
SQL_SMALL_RESULT that follow the SELECT keyword, and to
clauses such
as INTO, FOR UPDATE, and LOCK IN SHARE MODE.
The PROCEDURE clause cannot be used in a view definition,
and it cannot be used if a view is referenced in the FROM
clause.
If you create a view and then change the query processing
environment
by changing system variables, that may affect the results
that you get
from the view:
CREATE VIEW v (mycol) AS SELECT 'abc';
SET sql_mode = '';
SELECT "mycol" FROM v;
+-------+
| mycol |
+-------+
| mycol |
+-------+
SET sql_mode = 'ANSI_QUOTES';
SELECT "mycol" FROM v;
+-------+
| mycol |
+-------+
| abc |
+-------+
The DEFINER and SQL SECURITY clauses determine which MariaDB
account to
use when checking access privileges for the view when a
statement is
executed that references the view. They were added in MySQL
5.1.2.
The legal SQL SECURITY characteristic values are DEFINER and
INVOKER.
These indicate that the required privileges must be held by
the user
who defined or invoked the view, respectively. The default
SQL
SECURITY value is DEFINER.
If a user value is given for the DEFINER clause, it should
be a MariaDB
account in 'user_name'@'host_name' format (the same
format used in the
GRANT statement). The user_name and host_name values both
are
required. The definer can also be given as CURRENT_USER or
CURRENT_USER(). The default DEFINER value is the user who
executes the
CREATE VIEW statement. This is the same as specifying
DEFINER =
CURRENT_USER explicitly.
If you specify the DEFINER clause, these rules determine the
legal
DEFINER user values:
If you do not have the SUPER privilege, the only legal user
value is your own account, either specified literally or by
using CUR��x� RENT_USER. You cannot set the definer to some other
account.
If you have the SUPER privilege, you can specify any
syntactically legal account name. If the account does not
actually exist, a warning is generated.
If the SQL SECURITY value is DEFINER but the definer account
does not exist when the view is referenced, an error occurs.
Within a view definition, CURRENT_USER returns the view's
DEFINER
value by default. Before MySQL 5.1.12, and for views
defined with the SQL SECURITY INVOKER characteristic,
CURRENT_USER
returns the account for the view's invoker. For information
about user
auditing within views, see
http://dev.mysql.com/doc/refman/5.1/en/account-activity-auditing.html.
Within a stored routine that is defined with the SQL
SECURITY DEFINER
characteristic, CURRENT_USER returns the routine's DEFINER
value. This
also affects a view defined within such a program, if the
view
definition contains a DEFINER value of CURRENT_USER.
View privileges are checked like this:
At view definition time, the view creator must have the
privileges needed to use the top-level objects accessed by
the view. For example, if the view definition refers to
table columns, the creator must have privileges for the
columns, as described previously. If the definition refers
to a stored function, only the privileges needed to invoke
the function can be checked. The privileges required when
the function runs can be checked only as it executes: For
different invocations of the function, different execution
paths within the function might be taken.
When a view is referenced, privileges for objects accessed
by the view are checked against the privileges held by the
view creator or invoker, depending on whether the SQL
SECURITY characteristic is DEFINER or INVOKER, respectively.
If reference to a view causes execution of a stored
function, privilege checking for statements executed within
the function depend on whether the function is defined with
a SQL SECURITY characteristic of DEFINER or INVOKER. If the
security characteristic is DEFINER, the function runs with
the privileges of its creator. If the characteristic is
INVOKER, the function runs with the privileges determined by
the view's SQL SECURITY characteristic.
MySQL until 5.1.1
Prior to MySQL 5.1.2 (before the DEFINER and SQL SECURITY
clauses were
implemented), privileges required for objects used in a view
are
checked at view creation time.
Example: A view might depend on a stored function, and that
function
might invoke other stored routines. For example, the
following view
invokes a stored function f():
CREATE VIEW v AS SELECT * FROM t WHERE t.id = f(t.name);
Suppose that f() contains a statement such as this:
IF name IS NULL then
CALL p1();
ELSE
CALL p2();
END IF;
The privileges required for executing statements within f()
need to be
checked when f() executes. This might mean that privileges
are needed
for p1() or p2(), depending on the execution path within
f(). Those
privileges must be checked at runtime, and the user who must
possess
the privileges is determined by the SQL SECURITY values of
the view v
and the function f().
The DEFINER and SQL SECURITY clauses for views are
extensions to
standard SQL. In standard SQL, views are handled using the
rules for
SQL SECURITY INVOKER.
If you invoke a view that was created before MySQL 5.1.2, it
is
treated as though it was created with a SQL SECURITY DEFINER
clause
and with a DEFINER value that is the same as your account.
However,
because the actual definer is unknown, MySQL issues a
warning. To make
the warning go away, it is sufficient to re-create the view
so that
the view definition includes a DEFINER clause.
The optional ALGORITHM clause is an extension to standard
SQL. It
affects how MariaDB processes the view. ALGORITHM takes
three values:
MERGE, TEMPTABLE, or UNDEFINED. The default algorithm is
UNDEFINED if
no ALGORITHM clause is present. See View Algorithms for more
information.
Some views are updatable. That is, you can use them in
statements such
as UPDATE, DELETE, or INSERT to update the contents of the
underlying
table. For a view to be updatable, there must be a
one-to-one
relationship between the rows in the view and the rows in
the
underlying table. There are also certain other constructs
that make a
view non-updatable. See Inserting and Updating with Views.
WITH CHECK OPTION
The WITH CHECK OPTION clause can be given for an updatable
view to
prevent inserts or updates to rows except those for which
the WHERE
clause in the select_statement is true.
In a WITH CHECK OPTION clause for an updatable view, the
LOCAL and
CASCADED keywords determine the scope of check testing when
the view
is defined in terms of another view. The LOCAL keyword
restricts the
CHECK OPTION only to the view being defined. CASCADED causes
the
checks for underlying views to be evaluated as well. When
neither
keyword is given, the default is CASCADED.
For more information about updatable views and the WITH
CHECK OPTION
clause, see
Inserting and Updating with Views.
IF NOT EXISTS
The IF NOT EXISTS clause was added in MariaDB 10.1.3
When the IF NOT EXISTS clause is used, MariaDB will return a
warning instead of an error if the specified view already
exists. Cannot be used together with the OR REPLACE clause.
Examples
--------
CREATE TABLE t (a INT, b INT) ENGINE = InnoDB;
INSERT INTO t VALUES (1,1), (2,2), (3,3);
CREATE VIEW v AS SELECT a, a*2 AS a2 FROM t;
SELECT * FROM v;
+------+------+
| a | a2 |
+------+------+
| 1 | 2 |
| 2 | 4 |
| 3 | 6 |
+------+------+
OR REPLACE and IF NOT EXISTS:
CREATE VIEW v AS SELECT a, a*2 AS a2 FROM t;
ERROR 1050 (42S01): Table 'v' already exists
CREATE OR REPLACE VIEW v AS SELECT a, a*2 AS a2 FROM t;
Query OK, 0 rows affected (0.04 sec)
CREATE VIEW IF NOT EXISTS v AS SELECT a, a*2 AS a2 FROM t;
Query OK, 0 rows affected, 1 warning (0.01 sec)
SHOW WARNINGS;
+-------+------+--------------------------+
| Level | Code | Message |
+-------+------+--------------------------+
| Note | 1050 | Table 'v' already exists |
+-------+------+--------------------------+
URL: https://mariadb.com/kb/en/create-view/ %l� �= � G) ' DROP PROCEDURESyntax
------
DROP PROCEDURE [IF EXISTS] sp_name
Description
-----------
This statement is used to drop a stored procedure. That is,
the
specified routine is removed from the server along with all
privileges specific to the procedure. You must have the
ALTER ROUTINE privilege for the routine. If the
automatic_sp_privileges server system variable is set, that
privilege and EXECUTE are granted automatically to the
routine creator - see Stored Routine Privileges.
The IF EXISTS clause is a MySQL/MariaDB extension. It
prevents an error from occurring if the procedure or
function does not exist. A
NOTE is produced that can be viewed with SHOW WARNINGS.
While this statement takes effect immediately, threads which
are executing a procedure can continue execution.
Examples
--------
DROP PROCEDURE simpleproc;
IF EXISTS:
DROP PROCEDURE simpleproc;
ERROR 1305 (42000): PROCEDURE test.simpleproc does not exist
DROP PROCEDURE IF EXISTS simpleproc;
Query OK, 0 rows affected, 1 warning (0.00 sec)
SHOW WARNINGS;
+-------+------+------------------------------------------+
| Level | Code | Message |
+-------+------+------------------------------------------+
| Note | 1305 | PROCEDURE test.simpleproc does not exist |
+-------+------+------------------------------------------+
URL: https://mariadb.com/kb/en/drop-procedure/https://mariadb.com/kb/en/drop-procedure/ �
�( ' DROP SEQUENCEDROP SEQUENCE was introduced in MariaDB 10.3.
Syntax
------
DROP [TEMPORARY] SEQUENCE [IF EXISTS] [/*COMMENT TO SAVE*/]
sequence_name [, sequence_name] ...
Description
-----------
DROP SEQUENCE removes one or more sequences created with
CREATE SEQUENCE. You must have the DROP privilege for each
sequence. MariaDB returns an error indicating by name which
non-existing tables it was unable to drop, but it also drops
all of the tables in the list that do exist.
Important: When a table is dropped, user privileges on the
table are not automatically dropped. See GRANT.
If another connection is using the sequence, a metadata lock
is active, and this statement will wait until the lock is
released. This is also true for non-transactional tables.
For each referenced sequence, DROP SEQUENCE drops a
temporary sequence with that name, if it exists. If it does
not exist, and the TEMPORARY keyword is not used, it drops a
non-temporary sequence with the same name, if it exists. The
TEMPORARY keyword ensures that a non-temporary sequence will
not accidentally be dropped.
Use IF EXISTS to prevent an error from occurring for
sequences that do not exist. A NOTE is generated for each
non-existent sequence when using IF EXISTS. See SHOW
WARNINGS.
DROP SEQUENCE requires the DROP privilege.
Notes
DROP SEQUENCE only removes sequences, not tables. However,
DROP TABLE can remove both sequences and tables.
URL: https://mariadb.com/kb/en/drop-sequence/https://mariadb.com/kb/en/drop-sequence/ � �& ' DROP SERVERSyntax
------
DROP SERVER [ IF EXISTS ] server_name
Description
-----------
Drops the server definition for the server named
server_name. The
corresponding row within the mysql.servers table will be
deleted. This
statement requires the SUPER privilege.
Dropping a server for a table does not affect any
FederatedX, FEDERATED or Spider tables that used this
connection information when they were created.
IF EXISTS
If the IF EXISTS clause is used, MariaDB will not return an
error if the server does not exist. Unlike all other
statements, DROP SERVER IF EXISTS does not issue a note if
the server does not exist. See MDEV-9400.
Examples
--------
DROP SERVER s;
IF EXISTS:
DROP SERVER s;
ERROR 1477 (HY000): The foreign server name you are trying
to reference
does not exist. Data source error: s
DROP SERVER IF EXISTS s;
Query OK, 0 rows affected (0.00 sec)
URL: https://mariadb.com/kb/en/drop-server/https://mariadb.com/kb/en/drop-server/ � �' ' DROP TRIGGERSyntax
------
DROP TRIGGER [IF EXISTS] [schema_name.]trigger_name
Description
-----------
This statement drops a trigger. The schema (database) name
is optional. If the
schema is omitted, the trigger is dropped from the default
schema.
Its use requires the TRIGGER privilege for the table
associated with the trigger.
Use IF EXISTS to prevent an error from occurring for a
trigger that does not exist. A NOTE is generated for a
non-existent trigger
when using IF EXISTS. See SHOW WARNINGS.
Note: Triggers for a table are also dropped if you drop the
table.
Examples
--------
DROP TRIGGER test.example_trigger;
Using the IF EXISTS clause:
DROP TRIGGER IF EXISTS test.example_trigger;
Query OK, 0 rows affected, 1 warning (0.01 sec)
SHOW WARNINGS;
+-------+------+------------------------+
| Level | Code | Message |
+-------+------+------------------------+
| Note | 1360 | Trigger does not exist |
+-------+------+------------------------+
URL: https://mariadb.com/kb/en/drop-trigger/https://mariadb.com/kb/en/drop-trigger/ }2� �� �~� �� �
�% ' DROP TABLESyntax
------
DROP [TEMPORARY] TABLE [IF EXISTS] [/*COMMENT TO SAVE*/]
tbl_name [, tbl_name] ...
[WAIT n|NOWAIT]
[RESTRICT | CASCADE]
Description
-----------
DROP TABLE removes one or more tables. You must have the
DROP privilege
for each table. All table data and the table definition are
removed, as well as triggers associated to the table, so be
careful with this statement! If any of the tables named in
the argument list do
not exist, MariaDB returns an error indicating by name which
non-existing tables
it was unable to drop, but it also drops all of the tables
in the list that do
exist.
Important: When a table is dropped, user privileges on the
table are not
automatically dropped. See GRANT.
If another connection is using the table, a metadata lock is
active, and this statement will wait until the lock is
released. This is also true for non-transactional tables.
Note that for a partitioned table, DROP TABLE permanently
removes the table
definition, all of its partitions, and all of the data which
was stored in
those partitions. It also removes the partitioning
definition (.par) file
associated with the dropped table.
For each referenced table, DROP TABLE drops a temporary
table with that name, if it exists. If it does not exist,
and the TEMPORARY keyword is not used, it drops a
non-temporary table with the same name, if it exists. The
TEMPORARY keyword ensures that a non-temporary table will
not accidentally be dropped.
Use IF EXISTS to prevent an error from occurring for tables
that do not
exist. A NOTE is generated for each non-existent table when
using
IF EXISTS. See SHOW WARNINGS.
If a foreign key references this table, the table cannot be
dropped. In this case, it is necessary to drop the foreign
key first.
RESTRICT and CASCADE are allowed to make porting from other
database systems easier. In MariaDB, they do nothing.
Since MariaDB 5.5.27, the comment before the tablenames
(that /*COMMENT TO SAVE*/) is stored in the binary log. That
feature can be used by replication tools to send their
internal messages.
It is possible to specify table names as db_name.tab_name.
This is useful to delete tables from multiple databases with
one statement. See Identifier Qualifiers for details.
The DROP privilege is required to use DROP TABLE on
non-temporary tables. For temporary tables, no privilege is
required, because such tables are only visible for the
current session.
Note: DROP TABLE automatically commits the current active
transaction,
unless you use the TEMPORARY keyword.
WAIT/NOWAIT
Set the lock wait timeout. See WAIT and NOWAIT.
DROP TABLE in replication
DROP TABLE has the following characteristics in replication:
DROP TABLE IF EXISTS are always logged.
DROP TABLE without IF EXISTS for tables that don't exist
are not written to the binary log.
Dropping of TEMPORARY tables are prefixed in the log with
TEMPORARY. These drops are only logged when running
statement or mixed mode replication.
One DROP TABLE statement can be logged with up to 3
different DROP statements:
DROP TEMPORARY TABLE
list_of_non_transactional_temporary_tables
DROP TEMPORARY TABLE list_of_transactional_temporary_tables
DROP TABLE list_of_normal_tables
Starting from MariaDB 10.0.8, DROP TABLE on the master is
treated on the slave as DROP TABLE IF EXISTS. You can change
that by setting slave-ddl-exec-mode to STRICT.
Dropping an Internal #sql-... Table
If the mysqld process is killed during an ALTER TABLE you
may find a table named #sql-... in your data directory. In
MariaDB 10.3, InnoDB tables with this prefix will de deleted
automatically during startup.
In MariaDB 10.4 we will ensure that these temporary tables
will always be deleted automatically.
If you want to delete one of these tables explicitly you can
do so by using the following syntax:
DROP TABLE `#mysql50##sql-...`;
When running an ALTER TABLE…ALGORITHM=INPLACE that
rebuilds the table, InnoDB will create an internal #sql-ib
table. For these tables, the .frm file will be called
something else. In order to drop such a table after a server
crash, you must rename the #sql*.frm file to match the
#sql-ib*.ibd file.
Dropping All Tables in a Database
The best way to drop all tables in a database is by
executing DROP DATABASE, which will drop the database
itself, and all tables in it.
However, if you want to drop all tables in the database, but
you also want to keep the database itself and any other
non-table objects in it, then you would need to execute DROP
TABLE to drop each individual table. You can construct these
DROP TABLE commands by querying the TABLES table in the
information_schema database. For example:
SELECT CONCAT('DROP TABLE IF EXISTS `', TABLE_SCHEMA,
'`.`', TABLE_NAME, '`;')
FROM information_schema.TABLES
WHERE TABLE_SCHEMA = 'mydb';
Examples
--------
DROP TABLE Employees, Customers;
Notes
Beware that DROP TABLE can drop both tables and sequences.
This is mainly done to allow old tools like mysqldump to
work with sequences.
URL: https://mariadb.com/kb/en/drop-table/https://mariadb.com/kb/en/drop-table/ �B �G � $ ' DROP VIEWSyntax
------
DROP VIEW [IF EXISTS]
view_name [, view_name] ...
[RESTRICT | CASCADE]
Description
-----------
DROP VIEW removes one or more views. You must have the DROP
privilege for
each view. If any of the views named in the argument list do
not exist, MariaDB
returns an error indicating by name which non-existing views
it was unable to
drop, but it also drops all of the views in the list that do
exist.
The IF EXISTS clause prevents an error from occurring for
views that don't
exist. When this clause is given, a NOTE is generated for
each non-existent
view. See SHOW WARNINGS.
RESTRICT and CASCADE, if given, are parsed and ignored.
It is possible to specify view names as db_name.view_name.
This is useful to delete views from multiple databases with
one statement. See Identifier Qualifiers for details.
The DROP privilege is required to use DROP TABLE on
non-temporary tables. For temporary tables, no privilege is
required, because such tables are only visible for the
current session.
If a view references another view, it will be possible to
drop the referenced view. However, the other view will
reference a view which does not exist any more. Thus,
querying it will produce an error similar to the following:
ERROR 1356 (HY000): View 'db_name.view_name' references
invalid table(s) or
column(s) or function(s) or definer/invoker of view lack
rights to use them
This problem is reported in the output of CHECK TABLE.
Note that it is not necessary to use DROP VIEW to replace an
existing view, because CREATE VIEW has an OR REPLACE clause.
Examples
--------
DROP VIEW v,v2;
Given views v and v2, but no view v3
DROP VIEW v,v2,v3;
ERROR 1051 (42S02): Unknown table 'v3'
DROP VIEW IF EXISTS v,v2,v3;
Query OK, 0 rows affected, 1 warning (0.01 sec)
SHOW WARNINGS;
+-------+------+-------------------------+
| Level | Code | Message |
+-------+------+-------------------------+
| Note | 1051 | Unknown table 'test.v3' |
+-------+------+-------------------------+
URL: https://mariadb.com/kb/en/drop-view/https://mariadb.com/kb/en/drop-view/ � , ' Invisible ColumnsInvisible columns (sometimes also called hidden columns)
first appeared in MariaDB 10.3.3.
Columns can be given an INVISIBLE attribute in a CREATE
TABLE or ALTER TABLE statement. These columns will then not
be listed in the results of a SELECT * statement, nor do
they need to be assigned a value in an INSERT statement,
unless INSERT explicitly mentions them by name.
Since SELECT * does not return the invisible columns, new
tables or views created in this manner will have no trace of
the invisible columns. If specifically referenced in the
SELECT statement, the columns will be brought into the
view/new table, but the INVISIBLE attribute will not.
Invisible columns can be declared as NOT NULL, but then
require a DEFAULT value.
It is not possible for all columns in a table to be
invisible.
Examples
--------
CREATE TABLE t (x INT, y INT INVISIBLE, z INT INVISIBLE NOT
NULL);
ERROR 4106 (HY000): Invisible column `z` must have a default
value
CREATE TABLE t (x INT, y INT INVISIBLE, z INT INVISIBLE NOT
NULL DEFAULT 4);
INSERT INTO t VALUES (1),(2);
INSERT INTO t (x,y) VALUES (3,33);
SELECT * FROM t;
+------+
| x |
+------+
| 1 |
| 2 |
| 3 |
+------+
SELECT x,y,z FROM t;
+------+------+---+
| x | y | z |
+------+------+---+
| 1 | NULL | 4 |
| 2 | NULL | 4 |
| 3 | 33 | 4 |
+------+------+---+
DESC t;
+-------+---------+------+-----+---------+-----------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-----------+
| x | int(11) | YES | | NULL | |
| y | int(11) | YES | | NULL | INVISIBLE |
| z | int(11) | NO | | 4 | INVISIBLE |
+-------+---------+------+-----+---------+-----------+
ALTER TABLE t MODIFY x INT INVISIBLE, MODIFY y INT, MODIFY z
INT NOT NULL DEFAULT 4;
DESC t;
+-------+---------+------+-----+---------+-----------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-----------+
| x | int(11) | YES | | NULL | INVISIBLE |
| y | int(11) | YES | | NULL | |
| z | int(11) | NO | | 4 | |
+-------+---------+------+-----+---------+-----------+
Creating a view from a table with hidden columns:
CREATE VIEW v1 AS SELECT * FROM t;
DESC v1;
+-------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| x | int(11) | YES | | NULL | |
+-------+---------+------+-----+---------+-------+
CREATE VIEW v2 AS SELECT x,y,z FROM t;
DESC v2;
+-------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| x | int(11) | YES | | NULL | |
| y | int(11) | YES | | NULL | |
| z | int(11) | NO | | 4 | |
+-------+---------+------+-----+---------+-------+
URL: https://mariadb.com/kb/en/invisible-columns/https://mariadb.com/kb/en/invisible-columns/ Kb ?O�^ �3 � ' MERGEDescription
-----------
The MERGE storage engine, also known as the MRG_MyISAM
engine, is a
collection of identical MyISAM tables that can be used as
one.
"Identical" means that all tables have identical column
and index
information. You cannot merge MyISAM tables in which the
columns are
listed in a different order, do not have exactly the same
columns, or
have the indexes in different order. However, any or all of
the MyISAM
tables can be compressed with myisampack. Columns names and
indexes names can be different, as long as data types and
NULL/NOT NULL clauses are the same. Differences in
table options such as AVG_ROW_LENGTH, MAX_ROWS, or PACK_KEYS
do not
matter.
Each index in a MERGE table must match an index in
underlying MyISAM tables, but the opposite is not true.
Also, a MERGE table cannot have a PRIMARY KEY or UNIQUE
indexes, because it cannot enforce uniqueness over all
underlying tables.
The following options are meaningful for MERGE tables:
UNION. This option specifies the list of the underlying
MyISAM tables. The list is enclosed between parentheses and
separated with commas.
INSERT_METHOD. This options specifies whether, and how,
INSERTs are allowed for the table. Allowed values are: NO
(INSERTs are not allowed), FIRST (new rows will be written
into the first table specified in the UNION list), LAST (new
rows will be written into the last table specified in the
UNION list). The default value is NO.
If you define a MERGE table with a definition which is
different from the underlying MyISAM tables, or one of the
underlying tables is not MyISAM, the CREATE TABLE statement
will not return any error. But any statement which involves
the table will produce an error like the following:
ERROR 1168 (HY000): Unable to open underlying table which is
differently defined
or of non-MyISAM type or doesn't exist
A CHECK TABLE will show more information about the problem.
The error is also produced if the table is properly define,
but an underlying table's definition changes at some point
in time.
If you try to insert a new row into a MERGE table with
INSERT_METHOD=NO, you will get an error like the following:
ERROR 1036 (HY000): Table 'tbl_name' is read only
It is possible to build a MERGE table on MyISAM tables which
have one or more virtual columns. MERGE itself does not
support virtual columns, thus such columns will be seen as
regular columns. The data types and sizes will still need to
be identical, and they cannot be NOT NULL.
Examples
--------
CREATE TABLE t1 (
a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
message CHAR(20)) ENGINE=MyISAM;
CREATE TABLE t2 (
a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
message CHAR(20)) ENGINE=MyISAM;
INSERT INTO t1 (message) VALUES
('Testing'),('table'),('t1');
INSERT INTO t2 (message) VALUES
('Testing'),('table'),('t2');
CREATE TABLE total (
a INT NOT NULL AUTO_INCREMENT,
message CHAR(20), INDEX(a))
ENGINE=MERGE UNION=(t1,t2) INSERT_METHOD=LAST;
SELECT * FROM total;
+---+---------+
| a | message |
+---+---------+
| 1 | Testing |
| 2 | table |
| 3 | t1 |
| 1 | Testing |
| 2 | table |
| 3 | t2 |
+---+---------+
In the following example, we'll create three MyISAM tables,
and then a MERGE table on them. However, one of them uses a
different data type for the column b, so a SELECT will
produce an error:
CREATE TABLE t1 (
a INT,
b INT
) ENGINE = MyISAM;
CREATE TABLE t2 (
a INT,
b INT
) ENGINE = MyISAM;
CREATE TABLE t3 (
a INT,
b TINYINT
) ENGINE = MyISAM;
CREATE TABLE t_mrg (
a INT,
b INT
) ENGINE = MERGE,UNION=(t1,t2,t3);
SELECT * FROM t_mrg;
ERROR 1168 (HY000): Unable to open underlying table which is
differently defined
or of non-MyISAM type or doesn't exist
To find out what's wrong, we'll use a CHECK TABLE:
CHECK TABLE t_mrg;
+------------+-------+----------+-----------------------------------------------------------------------------------------------------+
| Table | Op | Msg_type | Msg_text |
+------------+-------+----------+-----------------------------------------------------------------------------------------------------+
| test.t_mrg | check | Error | Table 'test.t3' is
differently defined or of non-MyISAM type or doesn't exist
|
| test.t_mrg | check | Error | Unable to open underlying
table which is differently defined or of non-MyISAM type or
doesn't exist |
| test.t_mrg | check | error | Corrupt |
+------------+-------+----------+-----------------------------------------------------------------------------------------------------+
Now, we know that the problem is in t3's definition.
URL: https://mariadb.com/kb/en/merge/https://mariadb.com/kb/en/merge/ � "' ' RENAME TABLESyntax
------
RENAME TABLE tbl_name
[WAIT n | NOWAIT]
TO new_tbl_name
[, tbl_name2 TO new_tbl_name2] ...
Description
-----------
This statement renames one or more tables or views, but not
the privileges associated to them.
The rename operation is done atomically, which means that no
other session can
access any of the tables while the rename is running. For
example, if you have
an existing table old_table, you can create another table
new_table that has the same structure but is empty, and then
replace the existing table with the empty one as follows
(assuming that
backup_table does not already exist):
CREATE TABLE new_table (...);
RENAME TABLE old_table TO backup_table, new_table TO
old_table;
tbl_name can optionally be specified as db_name.tbl_name.
See Identifier Qualifiers. This allows to use RENAME to move
a table from a database to another (as long as they are on
the same filesystem):
RENAME TABLE db1.t TO db2.t;
Note that moving a table to another database is not possible
if it has some triggers. Trying to do so produces the
following error:
ERROR 1435 (HY000): Trigger in wrong schema
Also, views cannot be moved to another database:
ERROR 1450 (HY000): Changing schema from 'old_db' to
'new_db' is not allowed.
If a RENAME TABLE renames more than one table and one
renaming fails, all renames executed by the same statement
are rolled back.
Renames are always executed in the specified order. Knowing
this, it is also possible to swap two tables' names:
RENAME TABLE t1 TO tmp_table,
t2 TO t1,
tmp_table TO t2;
Privileges
Executing the RENAME TABLE statement requires the DROP,
CREATE and INSERT privileges for the table or the database.
WAIT/NOWAIT
Set the lock wait timeout. See WAIT and NOWAIT.
URL: https://mariadb.com/kb/en/rename-table/https://mariadb.com/kb/en/rename-table/ ^c R
�� ��
� O 0 ' Silent Column ChangesWhen a CREATE TABLE or ALTER TABLE command is issued,
MariaDB will silently change a column specification in the
following cases:
PRIMARY KEY columns are always NOT NULL.
Any trailing spaces from SET and ENUM values are discarded.
TIMESTAMP columns are always NOT NULL, and display sizes are
discarded
A row-size limit of 65535 bytes applies
If strict SQL mode is not enabled, a VARCHAR column longer
than 65535 become TEXT, and a VARBINARY columns longer than
65535 becomes a BLOB. If strict mode is enabled the silent
changes will not be made, and an error will occur.
If a USING clause specifies an index that's not permitted
by the storage engine, the engine will instead use another
available index type that can be applied without affecting
results.
If the CHARACTER SET binary attribute is specified, the
column is created as the matching binary data type. A TEXT
becomes a BLOB, CHAR a BINARY and VARCHAR a VARBINARY. ENUMs
and SETs are created as defined.
To ease imports from other RDBMS's, MariaDB will also
silently map the following data types:
Other Vendor Type | MariaDB Type |
BOOL | TINYINT |
BOOLEAN | TINYINT |
CHARACTER VARYING(M) | VARCHAR(M) |
FIXED | DECIMAL |
FLOAT4 | FLOAT |
FLOAT8 | DOUBLE |
INT1 | TINYINT |
INT2 | SMALLINT |
INT3 | MEDIUMINT |
INT4 | INT |
INT8 | BIGINT |
LONG VARBINARY | MEDIUMBLOB |
LONG VARCHAR | MEDIUMTEXT |
LONG | MEDIUMTEXT |
MIDDLEINT | MEDIUMINT |
NUMERIC | DECIMAL |
Currently, all MySQL types are supported in MariaDB.
For type mapping between Cassandra and MariaDB, see
Cassandra storage engine.
Example
Silent changes in action:
CREATE TABLE SilenceIsGolden
(
f1 TEXT CHARACTER SET binary,
f2 VARCHAR(15) CHARACTER SET binary,
f3 CHAR CHARACTER SET binary,
f4 ENUM('x','y','z') CHARACTER SET binary,
f5 VARCHAR (65536),
f6 VARBINARY (65536),
f7 INT1
);
Query OK, 0 rows affected, 2 warnings (0.31 sec)
SHOW WARNINGS;
+-------+------+-----------------------------------------------+
| Level | Code | Message |
+-------+------+-----------------------------------------------+
| Note | 1246 | Converting column 'f5' from VARCHAR to
TEXT |
| Note | 1246 | Converting column 'f6' from VARBINARY to
BLOB |
+-------+------+-----------------------------------------------+
DESCRIBE SilenceIsGolden;
+-------+-------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------------+------+-----+---------+-------+
| f1 | blob | YES | | NULL | |
| f2 | varbinary(15) | YES | | NULL | |
| f3 | binary(1) | YES | | NULL | |
| f4 | enum('x','y','z') | YES | | NULL | |
| f5 | mediumtext | YES | | NULL | |
| f6 | mediumblob | YES | | NULL | |
| f7 | tinyint(4) | YES | | NULL | |
+-------+-------------------+------+-----+---------+-------+
URL: https://mariadb.com/kb/en/silent-column-changes/https://mariadb.com/kb/en/silent-column-changes/ � �7 ( NEXT VALUE for sequence_nameSEQUENCEs were introduced in MariaDB 10.3
Syntax
------
NEXT VALUE FOR sequence
or
NEXTVAL(sequence_name)
or in Oracle mode (SQL_MODE=ORACLE)
sequence_name.nextval
NEXT VALUE FOR is ANSI SQL syntax while NEXTVAL() is
PostgreSQL syntax.
Description
-----------
Generate next value for a SEQUENCE.
You can greatly speed up NEXT VALUE by creating the sequence
with the CACHE option. If not, every NEXT VALUE usage will
cause changes in the stored SEQUENCE table.
When using NEXT VALUE the value will be reserved at once and
will not be reused, except if the SEQUENCE was created with
CYCLE. This means that when you are using SEQUENCEs you have
to expect gaps in the generated sequence numbers.
If one updates the SEQUENCE with SETVAL() or ALTER SEQUENCE
... RESTART, NEXT VALUE FOR will notice this and start from
the next requested value.
FLUSH TABLES will close the sequence and the next sequence
number generated will be according to what's stored in the
SEQUENCE object. In effect, this will discard the cached
values.
NEXT VALUE requires the INSERT privilege.
You can also use NEXT VALUE FOR sequence for column DEFAULT.
URL: https://mariadb.com/kb/en/next-value-for-sequence_name/https://mariadb.com/kb/en/next-value-for-sequence_name/ � �; ( PREVIOUS VALUE FOR sequence_nameSEQUENCEs were introduced in MariaDB 10.3.
Syntax
------
PREVIOUS VALUE FOR sequence_name
or
LASTVAL(sequence_name)
or in Oracle mode (SQL_MODE=ORACLE)
sequence_name.currval
PREVIOUS VALUE FOR is IBM DB2 syntax while LASTVAL() is
PostgreSQL syntax.
Description
-----------
Get last value in the current connection generated from a
sequence.
If the sequence has not yet been used by the connection,
PREVIOUS VALUE FOR returns NULL
If a SEQUENCE has been dropped and re-created then it's
treated as a new SEQUENCE and PREVIOUS VALUE FOR will return
NULL.
FLUSH TABLES has no effect on PREVIOUS VALUE FOR.
Previous values for all used sequences are stored per
connection until connection ends.
PREVIOUS VALUE FOR requires the SELECT privilege.
Example
SELECT PREVIOUS VALUE FOR s;
+----------------------+
| PREVIOUS VALUE FOR s |
+----------------------+
| 100 |
+----------------------+
URL:
https://mariadb.com/kb/en/previous-value-for-sequence_name/https://mariadb.com/kb/en/previous-value-for-sequence_name/ �;� � ʼ�� � � �) ' TRUNCATE TABLESyntax
------
TRUNCATE [TABLE] tbl_name
[WAIT n | NOWAIT]
Description
-----------
TRUNCATE TABLE empties a table completely. It requires the
DROP privilege. See GRANT.
tbl_name can also be specified in the form db_name.tbl_name
(see Identifier Qualifiers).
Logically, TRUNCATE TABLE is equivalent to a DELETE
statement that deletes all rows, but there are practical
differences under some circumstances.
TRUNCATE TABLE will fail for an InnoDB table if any FOREIGN
KEY constraints from other tables reference the table,
returning the error:
ERROR 1701 (42000): Cannot truncate a table referenced in a
foreign key constraint
Foreign Key constraints between columns in the same table
are permitted.
For an InnoDB table, if there are no FOREIGN KEY
constraints, InnoDB performs fast truncation by dropping the
original table and creating an empty one with the same
definition, which is much faster than deleting rows one by
one. The AUTO_INCREMENT counter is reset by TRUNCATE TABLE,
regardless of whether there is a FOREIGN KEY constraint.
The count of rows affected by TRUNCATE TABLE is accurate
only
when it is mapped to a DELETE statement.
For other storage engines, TRUNCATE TABLE differs from
DELETE in the following ways:
Truncate operations drop and re-create the table, which is
much
faster than deleting rows one by one, particularly for
large tables.
Truncate operations cause an implicit commit.
Truncation operations cannot be performed if the session
holds an
active table lock.
Truncation operations do not return a meaningful value for
the number
of deleted rows. The usual result is "0 rows affected,"
which should
be interpreted as "no information."
As long as the table format file tbl_name.frm is valid, the
table can be re-created as an empty table
with TRUNCATE TABLE, even if the data or index files have
become
corrupted.
The table handler does not remember the last
used AUTO_INCREMENT value, but starts counting
from the beginning. This is true even for MyISAM and
InnoDB, which normally
do not reuse sequence values.
When used with partitioned tables, TRUNCATE TABLE preserves
the partitioning; that is, the data and index files are
dropped and
re-created, while the partition definitions (.par) file is
unaffected.
Since truncation of a table does not make any use of DELETE,
the TRUNCATE statement does not invoke ON DELETE triggers.
TRUNCATE TABLE will only reset the values in the Performance
Schema summary tables to zero or null, and will not remove
the rows.
For the purposes of binary logging and replication, TRUNCATE
TABLE is treated as DROP TABLE followed by CREATE TABLE (DDL
rather than DML).
TRUNCATE TABLE does not work on views. Currently, TRUNCATE
TABLE drops all historical records from a system-versioned
table.
WAIT/NOWAIT
Set the lock wait timeout. See WAIT and NOWAIT.
Oracle-mode
Oracle-mode from MariaDB 10.3 permits the optional keywords
REUSE STORAGE or DROP STORAGE to be used.
TRUNCATE [TABLE] tbl_name [{DROP | REUSE} STORAGE]
These have no effect on the operation.
Performance
TRUNCATE TABLE is faster than DELETE, because it drops and
re-creates a table.
With XtraDB/InnoDB, TRUNCATE TABLE is slower if
innodb_file_per_table=ON is set (the default since MariaDB
5.5). This is because TRUNCATE TABLE unlinks the underlying
tablespace file, which can be an expensive operation. See
MDEV-8069 for more details.
The performance issues with innodb_file_per_table=ON can be
exacerbated in cases where the InnoDB buffer pool is very
large and innodb_adaptive_hash_index=ON is set. In that
case, using DROP TABLE followed by CREATE TABLE instead of
TRUNCATE TABLE may perform better. Setting
innodb_adaptive_hash_index=OFF can also help. In MariaDB
10.2.19 and later, this performance can also be improved by
setting innodb_safe_truncate=OFF. See MDEV-9459 for more
details.
Setting innodb_adaptive_hash_index=OFF can also improve
TRUNCATE TABLE performance in general. See MDEV-16796 for
more details.
URL: https://mariadb.com/kb/en/truncate-table/https://mariadb.com/kb/en/truncate-table/ � -?H ) Differences between JSON_QUERY and JSON_VALUEJSON functions were added in MariaDB 10.2.3.
The primary difference between the two functions is that
JSON_QUERY returns an object or an array, while JSON_VALUE
returns a scalar.
Take the following JSON document as an example
SET @json='{ "x": [0,1], "y": "[0,1]", "z":
"Monty" }';
Note that data member "x" is an array, and data members
"y" and "z" are strings. The following examples
demonstrate the differences between the two functions.
SELECT JSON_QUERY(@json,'$'), JSON_VALUE(@json,'$');
+--------------------------------------------+-----------------------+
| JSON_QUERY(@json,'$') | JSON_VALUE(@json,'$') |
+--------------------------------------------+-----------------------+
| { "x": [0,1], "y": "[0,1]", "z": "Monty" } |
NULL |
+--------------------------------------------+-----------------------+
SELECT JSON_QUERY(@json,'$.x'), JSON_VALUE(@json,'$.x');
+-------------------------+-------------------------+
| JSON_QUERY(@json,'$.x') | JSON_VALUE(@json,'$.x') |
+-------------------------+-------------------------+
| [0,1] | NULL |
+-------------------------+-------------------------+
SELECT JSON_QUERY(@json,'$.y'), JSON_VALUE(@json,'$.y');
+-------------------------+-------------------------+
| JSON_QUERY(@json,'$.y') | JSON_VALUE(@json,'$.y') |
+-------------------------+-------------------------+
| NULL | [0,1] |
+-------------------------+-------------------------+
SELECT JSON_QUERY(@json,'$.z'), JSON_VALUE(@json,'$.z');
+-------------------------+-------------------------+
| JSON_QUERY(@json,'$.z') | JSON_VALUE(@json,'$.z') |
+-------------------------+-------------------------+
| NULL | Monty |
+-------------------------+-------------------------+
SELECT JSON_QUERY(@json,'$.x[0]'),
JSON_VALUE(@json,'$.x[0]');
+----------------------------+----------------------------+
| JSON_QUERY(@json,'$.x[0]') |
JSON_VALUE(@json,'$.x[0]') |
+----------------------------+----------------------------+
| NULL | 0 |
+----------------------------+----------------------------+
URL:
https://mariadb.com/kb/en/differences-between-json_query-and-json_value/https://mariadb.com/kb/en/differences-between-json_query-and-json_value/ -� !s�,M Syntax
------
[GENERATED ALWAYS] AS ( )
[VIRTUAL | PERSISTENT | STORED] [UNIQUE] [UNIQUE KEY]
[COMMENT ]
MariaDB's generated columns syntax is designed to be
similar to the syntax for Microsoft SQL Server's computed
columns and Oracle Database's virtual columns. In MariaDB
10.2 and later, the syntax is also compatible with the
syntax for MySQL's generated columns.
Description
-----------
A generated column is a column in a table that cannot
explicitly be set to a specific value in a DML query.
Instead, its value is automatically generated based on an
expression. This expression might generate the value based
on the values of other columns in the table, or it might
generate the value by calling built-in functions or
user-defined functions (UDFs).
There are two types of generated columns:
PERSISTENT or STORED: This type's value is actually stored
in the table.
VIRTUAL: This type's value is not stored at all. Instead,
the value is generated dynamically when the table is
queried. This type is the default.
Generated columns are also sometimes called computed columns
or virtual columns.
Supported Features
Storage Engine Support
Generated columns can only be used with storage engines
which support them. If you try to use a storage engine that
does not support them, then you will see an error similar to
the following:
ERROR 1910 (HY000): TokuDB storage engine does not support
computed columns
InnoDB, Aria, MyISAM and CONNECT support generated columns.
A column in a MERGE table can be built on a PERSISTENT
generated column.
However, a column in a MERGE table can not be defined as a
VIRTUAL and PERSISTENT generated column.
Data Type Support
All data types are supported when defining generated
columns.
Using the ZEROFILL column option is supported when defining
generated columns.
In MariaDB 10.2.6 and later, the following statements apply
to data types for generated columns:
Using the AUTO_INCREMENT column option is not supported when
defining generated columns. Previously, it was supported,
but this support was removed, because it would not work
correctly. See MDEV-11117.
Index Support
Using a generated column as a table's primary key is not
supported. See MDEV-5590 for more information. If you try to
use one as a primary key, then you will see an error similar
to the following:
ERROR 1903 (HY000): Primary key cannot be defined upon a
computed column
Using PERSISTENT generated columns as part of a foreign key
is supported.
Referencing PERSISTENT generated columns as part of a
foreign key is also supported.
However, using the ON UPDATE CASCADE, ON UPDATE SET NULL, or
ON DELETE SET NULL clauses is not supported. If you try to
use an unsupported clause, then you will see an error
similar to the following:
ERROR 1905 (HY000): Cannot define foreign key with ON UPDATE
SET NULL clause on a computed column
In MariaDB 10.2.3 and later, the following statements apply
to indexes for generated columns:
Defining indexes on both VIRTUAL and PERSISTENT generated
columns is supported.
If an index is defined on a generated column, then the
optimizer considers using it in the same way as indexes
based on "real" columns.
MariaDB until 10.2.2
In MariaDB 10.2.2 and before, the following statements apply
to indexes for generated columns:
Defining indexes on VIRTUAL generated columns is not
supported.
Defining indexes on PERSISTENT generated columns is
supported.
If an index is defined on a generated column, then the
optimizer considers using it in the same way as indexes
based on "real" columns.
Statement Support
Generated columns are used in DML queries just as if they
were "real" columns.
However, VIRTUAL and PERSISTENT generated columns differ in
how their data is stored.
Values for PERSISTENT generated columns are generated
whenever a DML queries inserts or updates the row with the
special DEFAULT value. This generates the columns value, and
it is stored in the table like the other "real" columns.
This value can be read by other DML queries just like the
other "real" columns.
Values for VIRTUAL generated columns are not stored in the
table. Instead, the value is generated dynamically whenever
the column is queried. If other columns in a row are
queried, but the VIRTUAL generated column is not one of the
queried columns, then the column's value is not generated.
The SELECT statement supports generated columns.
Generated columns can be referenced in the INSERT, UPDATE,
and DELETE statements.
However, VIRTUAL or PERSISTENT generated columns cannot be
explicitly set to any other values than NULL or DEFAULT. If
a generated column is explicitly set to any other value,
then the outcome depends on whether strict mode is enabled
in SQL_MODE. If it is not enabled, then a warning will be
raised and the default generated value will be used instead.
If it is enabled, then an error will be raised instead.
The CREATE TABLE statement has limited support for generated
columns.
It supports defining generated columns in a new table.
It supports using generated columns to partition tables.
It does not support using the versioning clauses with
generated columns.
The ALTER TABLE statement has limited support for generated
columns.
It supports the MODIFY and CHANGE clauses for PERSISTENT
generated columns.
It does not support the MODIFY clause for VIRTUAL generated
columns if ALGORITHM is not set to COPY. See MDEV-15476 for
more information.
It does not support the CHANGE clause for VIRTUAL generated
columns if ALGORITHM is not set to COPY. See MDEV-17035 for
more information.
It does not support altering a table if ALGORITHM is not set
to COPY if the table has a VIRTUAL generated column that is
indexed. See MDEV-14046 for more information.
It does not support adding a VIRTUAL generated column with
the ADD clause if the same statement is also adding other
columns if ALGORITHM is not set to COPY. See MDEV-17468 for
more information.
It also does not support altering an existing column into a
VIRTUAL generated column.
It supports using generated columns to partition tables.
It does not support using the versioning clauses with
generated columns.
The SHOW CREATE TABLE statement supports generated columns.
The DESCRIBE statement can be used to check whether a table
has generated columns.
You can tell which columns are generated by looking for the
ones where the Extra column is set to either VIRTUAL or
PERSISTENT. For example:
DESCRIBE table1;
+-------+-------------+------+-----+---------+------------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+------------+
| a | int(11) | NO | | NULL | |
| b | varchar(32) | YES | | NULL | |
| c | int(11) | YES | | NULL | VIRTUAL |
| d | varchar(5) | YES | | NULL | PERSISTENT |
+-------+-------------+------+-----+---------+------------+
Generated columns can be properly referenced in the NEW and
OLD rows in triggers.
Stored procedures support generated columns.
The HANDLER statement supports generated columns.
Expression Support
Most legal, deterministic expressions which can be
calculated are supported in expressions for generated
columns.
Most built-in functions are supported in expressions for
generated columns.
However, some built-in functions can't be supported for
technical reasons. For example, If you try to use an
unsupported function in an expression, then you will see an
error similar to the following:
ERROR 1901 (HY000): Function or expression 'dayname()'
cannot be used in the GENERATED ALWAYS AS clause of `v`
Subqueries are not supported in expressions for generated
columns because the underlying data can change.
Using anything that depends on data outside the row is not
supported in expressions for generated columns.
Stored functions are not supported in expressions for
generated columns. See MDEV-17587 for more information.
In MariaDB 10.2.1 and later, the following statements apply
to expressions for generated columns:
Non-deterministic built-in functions are supported in
expressions for PERSISTENT generated columns.
If a non-deterministic function is used for a PERSISTENT
generated column, th��*B en any changes made to this table should
be logged to the binary log in the row-based logging format
when the binlog_format system variable is set to MIXED.
However, this does not always happen. Therefore, it is
recommended to set the binlog_format system variable to ROW.
See MDEV-10436 for more information.
Non-deterministic built-in functions are not supported in
expressions for VIRTUAL generated columns.
User-defined functions (UDFs) are supported in expressions
for generated columns.
However, MariaDB can't check whether a UDF is
deterministic, so it is up to the user to be sure that they
do not use non-deterministic UDFs with VIRTUAL generated
columns.
Defining a generated column based on other generated columns
defined before it in the table definition is supported. For
example:
CREATE TABLE t1 (a int as (1), b int as (a));
However, defining a generated column based on other
generated columns defined after in the table definition is
not supported in expressions for generation columns because
generated columns are calculated in the order they are
defined.
Using an expression that exceeds 255 characters in length is
supported in expressions for generated columns. The new
limit for the entire table definition, including all
expressions for generated columns, is 65,535 bytes.
Using constant expressions is supported in expressions for
generated columns. For example:
CREATE TABLE t1 (a int as (1));
MariaDB until 10.2.0
In MariaDB 10.2.0 and before, the following statements apply
to expressions for generated columns:
Non-deterministic built-in functions are not supported in
expressions for generated columns.
User-defined functions (UDFs) are not supported in
expressions for generated columns.
Defining a generated column based on other generated columns
defined in the table is not supported. Otherwise, it would
generate errors like this:
ERROR 1900 (HY000): A computed column cannot be based on a
computed column
Using an expression that exceeds 255 characters in length is
not supported in expressions for generated columns.
Using constant expressions is not supported in expressions
for generated columns. Otherwise, it would generate errors
like this:
ERROR 1908 (HY000): Constant expression in computed column
function is not allowed
MySQL Compatibility Support
In MariaDB 10.2.1 and later, the following statements apply
to MySQL compatibility for generated columns:
The STORED keyword is supported as an alias for the
PERSISTENT keyword.
Tables created with MySQL 5.7 or later that contain MySQL's
generated columns can be imported into MariaDB without a
dump and restore.
MariaDB until 10.2.0
In MariaDB 10.2.0 and before, the following statements apply
to MySQL compatibility for generated columns:
The STORED keyword is not supported as an alias for the
PERSISTENT keyword.
Tables created with MySQL 5.7 or later that contain MySQL's
generated columns can not be imported into MariaDB without a
dump and restore.
Implementation Differences
Generated columns are subject to various constraints in
other DBMSs that are not present in MariaDB's
implementation. Generated columns may also be called
computed columns or virtual columns in different
implementations. The various details for a specific
implementation can be found in the documentation for each
specific DBMS.
Implementation Differences Compared to Microsoft SQL Server
MariaDB's generated columns implementation does not enforce
the following
restrictions that are present in Microsoft SQL Server's
computed columns implementation:
MariaDB allows server variables in generated column
expressions, including those that change dynamically, such
as warning_count.
MariaDB allows the CONVERT_TZ() function to be called with a
named time zone as an argument, even though time zone names
and time offsets are configurable.
MariaDB allows the CAST() function to be used with
non-unicode character sets, even though character sets are
configurable and differ between binaries/versions.
MariaDB allows FLOAT expressions to be used in generated
columns. Microsoft SQL Server considers these expressions to
be "imprecise" due to potential cross-platform differences
in floating-point implementations and precision.
Microsoft SQL Server requires the ARITHABORT mode to be set,
so that division by zero returns an error, and not a NULL.
Microsoft SQL Server requires QUOTED_IDENTIFIER to be set in
SQL_MODE. In MariaDB, if data is inserted without
ANSI_QUOTES set in SQL_MODE, then it will be processed and
stored differently in a generated column that contains
quoted identifiers.
In MariaDB 10.2.0 and before, it does not allow user-defined
functions (UDFs) to be used in expressions for generated
columns.
Microsoft SQL Server enforces the above restrictions by
doing one of the following things:
Refusing to create computed columns.
Refusing to allow updates to a table containing them.
Refusing to use an index over such a column if it can not be
guaranteed that the expression is fully deterministic.
In MariaDB, as long as the SQL_MODE, language, and other
settings that were in effect during the CREATE TABLE remain
unchanged, the generated column expression will always be
evaluated the same. If any of these things change, then
please be aware that the generated column expression might
not be
evaluated the same way as it previously was.
In MariaDB 5.2, you will get a warning if you try to update
a virtual column. In MariaDB 5.3 and later, this warning
will be converted to an error if strict mode is enabled in
SQL_MODE.
Development History
Generated columns was originally developed by Andrey Zhakov.
It was then modified by Sanja Byelkin and Igor Babaev at
Monty Program for inclusion in MariaDB. Monty did the work
on MariaDB 10.2 to lift a some of the old limitations.
Examples
--------
Here is an example table that uses both VIRTUAL and
PERSISTENT virtual columns:
USE TEST;
CREATE TABLE table1 (
a INT NOT NULL,
b VARCHAR(32),
c INT AS (a mod 10) VIRTUAL,
d VARCHAR(5) AS (left(b,5)) PERSISTENT);
If you describe the table, you can easily see which columns
are virtual by
looking in the "Extra" column:
DESCRIBE table1;
+-------+-------------+------+-----+---------+------------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+------------+
| a | int(11) | NO | | NULL | |
| b | varchar(32) | YES | | NULL | |
| c | int(11) | YES | | NULL | VIRTUAL |
| d | varchar(5) | YES | | NULL | PERSISTENT |
+-------+-------------+------+-----+---------+------------+
To find out what function(s) generate the value of the
virtual column you can use SHOW CREATE TABLE:
SHOW CREATE TABLE table1;
| table1 | CREATE TABLE `table1` (
`a` int(11) NOT NULL,
`b` varchar(32) DEFAULT NULL,
`c` int(11) AS (a mod 10) VIRTUAL,
`d` varchar(5) AS (left(b,5)) PERSISTENT
) ENGINE=MyISAM DEFAULT CHARSET=latin1 |
If you try to insert non-default values into a virtual
column, you will receive
a warning and what you tried to insert will be ignored and
the derived value
inserted instead:
WARNINGS;
Show warnings enabled.
INSERT INTO table1 VALUES (1, 'some
text',default,default);
Query OK, 1 row affected (0.00 sec)
INSERT INTO table1 VALUES (2, 'more text',5,default);
Query OK, 1 row affected, 1 warning (0.00 sec)
Warning (Code 1645): The value specified for computed column
'c' in table 'table1' has been ignored.
INSERT INTO table1 VALUES (123, 'even more
text',default,'something');
Query OK, 1 row affected, 2 warnings (0.00 sec)
Warning (Code 1645): The value specified for computed column
'd' in table 'table1' has been ignored.
Warning (Code 1265): Data truncated for column 'd' at row
1
SELECT * FROM table1;
+-----+----------------+------+-------+
| a | b | c | d |
+-----+----------------+------+-------+
| 1 | some text | 1 | some |
| 2 | more text | 2 | more |
| 123 | even more text | 3 | even |
+-----+----------------+------+-------+
3 rows in set (0.00 sec)
If the ZEROFILL clause is specified, it should be placed
directly after the type definition, before the AS ():
CREATE TABLE table2 (a INT, b INT ZEROFILL AS (a*2)
VIRTU��� �� � � , ( Sequence OverviewSequences were introduced in MariaDB 10.3.
Introduction
A sequence is an object that generates a sequence of numeric
values, as specified by the CREATE SEQUENCE statement.
CREATE SEQUENCE will create a sequence that generates new
values when called with NEXT VALUE FOR sequence_name. It's
an alternative to AUTO INCREMENT when one wants to have more
control of how the numbers are generated. As the SEQUENCE
caches values (up to the CACHE value in the CREATE SEQUENCE
statement, by default 1000) it can in some cases be much
faster than AUTO INCREMENT. Another benefit is that one can
access the last value generated by all used sequences, which
solves one of the limitations with LAST_INSERT_ID().
Creating a Sequence
The CREATE SEQUENCE statement is used to create a sequence.
Here is an example of a sequence starting at 100,
incrementing by 10 each time:
CREATE SEQUENCE s START WITH 100 INCREMENT BY 10;
The CREATE SEQUENCE statement, along with defaults, can be
viewd with the SHOW CREATE SEQUENCE STATEMENT, for example:
SHOW CREATE SEQUENCE s\G
*************************** 1. row
***************************
Table: s
Create Table: CREATE SEQUENCE `s` start with 100 minvalue 1
maxvalue 9223372036854775806
increment by 10 cache 1000 nocycle ENGINE=InnoDB
Using Sequence Objects
To get the next value from a sequence, use
NEXT VALUE FOR sequence_name
or
NEXTVAL(sequence_name)
or in Oracle mode (SQL_MODE=ORACLE)
sequence_name.nextval
For retrieving the last value used by the current connection
from a sequence
use:
PREVIOUS VALUE FOR sequence_name
or
LASTVAL(sequence_name)
or in Oracle mode (SQL_MODE=ORACLE)
sequence_name.currval
For example:
SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
| 100 |
+------------+
SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
| 110 |
+------------+
SELECT LASTVAL(s);
+------------+
| LASTVAL(s) |
+------------+
| 110 |
+------------+
Using Sequences in DEFAULT
Starting from 10.3.3 you can use Sequences in DEFAULT:
create sequence s1;
create table t1 (a int primary key default (next value for
s1), b int);
insert into t1 (b) values (1),(2);
select * from t1;
+---+------+
| a | b |
+---+------+
| 1 | 1 |
| 2 | 2 |
+---+------+
Changing a Sequence
The ALTER SEQUENCE statement is used for changing sequences.
For example, to restart the sequence at another value:
ALTER SEQUENCE s RESTART 50;
SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
| 50 |
+------------+
The SETVAL function can also be used to set the next value
to be returned for a SEQUENCE, for example:
SELECT SETVAL(s, 100);
+----------------+
| SETVAL(s, 100) |
+----------------+
| 100 |
+----------------+
SETVAL can only be used to increase the sequence value.
Attempting to set a lower value will fail, returning NULL:
SELECT SETVAL(s, 50);
+---------------+
| SETVAL(s, 50) |
+---------------+
| NULL |
+---------------+
Dropping a Sequence
The DROP SEQUENCE statement is used to drop a sequence, for
example:
DROP SEQUENCE s;
Replication
If one wants to use Sequences in a master-master setup or
with Galera one
should use INCREMENT=0. This will tell the Sequence to use
auto_increment_increment and auto_increment_offset to
generate unique values for each server.
Standards Compliance
MariaDB 10.3 supports both ANSI SQL and Oracle syntax for
sequences.
However as SEQUENCE is implemented as a special kind of
table, it uses the same namespace as tables. The benefits
are that sequences show up in SHOW TABLES, and one can also
create a sequence with CREATE TABLE and drop it with DROP
TABLE. One can SELECT from it as from any other table. This
ensures that all old tools that work with tables should work
with sequences.
Since sequence objects act as regular tables in many
contexts, they will be affected by LOCK TABLES. This is not
the case in other DBMS, such as Oracle, where LOCK TABLE
does not affect sequences.
Notes
One of the goals with the Sequence implementation is that
all old
tools, such as mysqldump, should work unchanged, while still
keeping the
normal usage of sequence standard compatibly.
To make this possible, sequence is currently implemented as
a table with a few exclusive properties.
The special properties for sequence tables are:
A sequence table has always one row.
When one creates a sequence, either with CREATE TABLE or
CREATE SEQUENCE, one row will be inserted.
If one tries to insert into a sequence table, the single row
will be updated. This allows mysqldump to work but also
gives the additional benefit that one can change all
properties of a sequence with a single insert. New
applications should of course also use ALTER SEQUENCE.
UPDATE or DELETE can't be performed on Sequence objects.
Doing a select on the sequence shows the current state of
the sequence, except the values that are reserved in the
cache. The next_value column shows the next value not
reserved by the cache.
FLUSH TABLES will close the sequence and the next sequence
number generated will be according to what's stored in the
Sequence object. In effect, this will discard the cached
values.
A number of normal table operations work on Sequence tables.
See next section.
Table Operations that Work with Sequences
SHOW CREATE TABLE sequence_name. This shows the table
structure that is behind the SEQUENCE including the field
names that can be used with SELECT or even CREATE TABLE.
CREATE TABLE sequence-structure ... SEQUENCE=1
ALTER TABLE sequence RENAME TO sequence2
RENAME TABLE sequence_name TO new_sequence_name
DROP TABLE sequence_name. This is allowed mainly to get old
tools like mysqldump to work with sequence tables.
SHOW TABLES
Implementation
Internally, sequence tables are created as a normal table
without
rollback (the InnoDB, Aria and MySAM engines support this),
wrapped by a
sequence engine object. This allowed us to create sequences
with
almost no performance impact for normal tables. (The cost is
one 'if'
per insert if the binary log is enabled).
Underlying Table Structure
The following example shows the table structure of sequences
and how it
can be used as a table.
(Output of results are slightly edited to make them easier
to read)
create sequence t1;
show create sequence t1\G
***** 1. row *****
CREATE SEQUENCE `t1` start with 1 minvalue 1 maxvalue
9223372036854775806
increment by 1 cache 1000 nocycle ENGINE=InnoDB
show create table t1\G
***** 1. row *****
Create Table: CREATE TABLE `t1` (
`next_not_cached_value` bigint(21) NOT NULL,
`minimum_value` bigint(21) NOT NULL,
`maximum_value` bigint(21) NOT NULL,
`start_value` bigint(21) NOT NULL COMMENT 'start value
when sequences is created or value if RESTART is used',
`increment` bigint(21) NOT NULL COMMENT 'increment
value',
`cache_size` bigint(21) unsigned NOT NULL,
`cycle_option` tinyint(1) unsigned NOT NULL COMMENT '0 if
no cycles are allowed, 1 if the sequence should begin a new
cycle when maximum_value is passed',
`cycle_count` bigint(21) NOT NULL COMMENT 'How many cycles
have been done'
) ENGINE=InnoDB SEQUENCE=1
select * from t1\G
next_not_cached_value: 1
minimum_value: 1
maximum_value: 9223372036854775806
start_value: 1
increment: 1
cache_size: 1000
cycle_option: 0
cycle_count: 0
The cycle_count column is incremented every time the
sequence wraps around.
Credits
Thanks to Jianwe Zhao from Aliyun for his work on SEQUENCE
in AliSQL, which gave ideas and inspiration for this work.
Thanks to Peter Gulutzan,who helped test and gave useful
comments about the implementation.
URL: https://mariadb.com/kb/en/sequence-overview/https://mariadb.com/kb/en/sequence-overview/ : Up�� �o
� T
! ( SETVAL()SEQUENCEs were introduced in MariaDB 10.3.
Syntax
------
SETVAL(sequence_name, next_value, [is_used, [round]])
Description
-----------
Set the next value to be returned for a SEQUENCE.
This function is compatible with PostgreSQL syntax, extended
with the round argument.
If the is_used argument is not given or is 1 or true, then
the next used value will
one after the given value. If is_used is 0 or false then the
next generated value
will be the given value.
If round is used then it will set the round value (or the
internal cycle count, starting at zero) for the sequence.
If round is not used, it's assumed to be 0.
next_value must be an integer literal.
For SEQUENCE tables defined with CYCLE (see CREATE SEQUENCE)
one should use both next_value and round to define the next
value. In this case the
current sequence value is defined to be round, next_value.
The result returned by SETVAL() is next_value or NULL if the
given next_value and round is smaller than the current
value.
SETVAL() will not set the SEQUENCE value to a something that
is less than
its current value. This is needed to ensure that SETVAL()
is replication safe. If you want to set the SEQUENCE to a
smaller number
use ALTER SEQUENCE.
If CYCLE is used, first round and then next_value are
compared
to see if the value is bigger than the current value.
Internally, in the MariaDB server, SETVAL() is used to
inform
slaves that a SEQUENCE has changed value. The slave may get
SETVAL() statements out of order, but this is ok as only the
biggest one will have an effect.
SETVAL requires the INSERT privilege.
Examples
--------
SELECT setval(foo, 42); -- Next nextval will return 43
SELECT setval(foo, 42, true); -- Same as above
SELECT setval(foo, 42, false); -- Next nextval will return
42
SETVAL setting higher and lower values on a sequence with an
increment of 10:
SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
| 50 |
+------------+
SELECT SETVAL(s, 100);
+----------------+
| SETVAL(s, 100) |
+----------------+
| 100 |
+----------------+
SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
| 110 |
+------------+
SELECT SETVAL(s, 50);
+---------------+
| SETVAL(s, 50) |
+---------------+
| NULL |
+---------------+
SELECT NEXTVAL(s);
+------------+
| NEXTVAL(s) |
+------------+
| 120 |
+------------+
Example demonstrating round:
CREATE OR REPLACE SEQUENCE s1
START WITH 1
MINVALUE 1
MAXVALUE 99
INCREMENT BY 1
CACHE 20
CYCLE;
SELECT SETVAL(s1, 99, 1, 0);
+----------------------+
| SETVAL(s1, 99, 1, 0) |
+----------------------+
| 99 |
+----------------------+
SELECT NEXTVAL(s1);
+-------------+
| NEXTVAL(s1) |
+-------------+
| 1 |
+-------------+
The following statement returns NULL, as the given
next_value and round is smaller than the current value.
SELECT SETVAL(s1, 99, 1, 0);
+----------------------+
| SETVAL(s1, 99, 1, 0) |
+----------------------+
| NULL |
+----------------------+
SELECT NEXTVAL(s1);
+-------------+
| NEXTVAL(s1) |
+-------------+
| 2 |
+-------------+
Increasing the round from zero to 1 will allow next_value to
be returned.
SELECT SETVAL(s1, 99, 1, 1);
+----------------------+
| SETVAL(s1, 99, 1, 1) |
+----------------------+
| 99 |
+----------------------+
SELECT NEXTVAL(s1);
+-------------+
| NEXTVAL(s1) |
+-------------+
| 1 |
+-------------+
URL: https://mariadb.com/kb/en/setval/https://mariadb.com/kb/en/setval/ � �, ) JSON_ARRAY_APPENDJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_ARRAY_APPEND(json_doc, path, value[, path, value] ...)
Description
-----------
Appends values to the end of the specified arrays within a
JSON document, returning the result, or NULL if any of the
arguments are NULL.
Evaluation is performed from left to right, with the
resulting document from the previous pair becoming the new
value against which the next pair is evaluated.
If the json_doc is not a valid JSON document, or if any of
the paths are not valid, or contain a * or ** wildcard, an
error is returned.
Examples
--------
SET @json = '[1, 2, [3, 4]]';
SELECT JSON_ARRAY_APPEND(@json, '$[0]', 5)
+-------------------------------------+
| JSON_ARRAY_APPEND(@json, '$[0]', 5) |
+-------------------------------------+
| [[1, 5], 2, [3, 4]] |
+-------------------------------------+
SELECT JSON_ARRAY_APPEND(@json, '$[1]', 6);
+-------------------------------------+
| JSON_ARRAY_APPEND(@json, '$[1]', 6) |
+-------------------------------------+
| [1, [2, 6], [3, 4]] |
+-------------------------------------+
SELECT JSON_ARRAY_APPEND(@json, '$[1]', 6, '$[2]', 7);
+------------------------------------------------+
| JSON_ARRAY_APPEND(@json, '$[1]', 6, '$[2]', 7) |
+------------------------------------------------+
| [1, [2, 6], [3, 4, 7]] |
+------------------------------------------------+
SELECT JSON_ARRAY_APPEND(@json, '$', 5);
+----------------------------------+
| JSON_ARRAY_APPEND(@json, '$', 5) |
+----------------------------------+
| [1, 2, [3, 4], 5] |
+----------------------------------+
SET @json = '{"A": 1, "B": [2], "C": [3, 4]}';
SELECT JSON_ARRAY_APPEND(@json, '$.B', 5);
+------------------------------------+
| JSON_ARRAY_APPEND(@json, '$.B', 5) |
+------------------------------------+
| {"A": 1, "B": [2, 5], "C": [3, 4]} |
+------------------------------------+
URL: https://mariadb.com/kb/en/json_array_append/https://mariadb.com/kb/en/json_array_append/ �
� �
�F� �� � �, ) JSON_ARRAY_INSERTJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_ARRAY_INSERT(json_doc, path, value[, path, value] ...)
Description
-----------
Inserts a value into a JSON document, returning the modified
document, or NULL if any of the arguments are NULL.
Evaluation is performed from left to right, with the
resulting document from the previous pair becoming the new
value against which the next pair is evaluated.
If the json_doc is not a valid JSON document, or if any of
the paths are not valid, or contain a * or ** wildcard, an
error is returned.
Examples
--------
SET @json = '[1, 2, [3, 4]]';
SELECT JSON_ARRAY_INSERT(@json, '$[0]', 5);
+-------------------------------------+
| JSON_ARRAY_INSERT(@json, '$[0]', 5) |
+-------------------------------------+
| [5, 1, 2, [3, 4]] |
+-------------------------------------+
SELECT JSON_ARRAY_INSERT(@json, '$[1]', 6);
+-------------------------------------+
| JSON_ARRAY_INSERT(@json, '$[1]', 6) |
+-------------------------------------+
| [1, 6, 2, [3, 4]] |
+-------------------------------------+
SELECT JSON_ARRAY_INSERT(@json, '$[1]', 6, '$[2]', 7);
+------------------------------------------------+
| JSON_ARRAY_INSERT(@json, '$[1]', 6, '$[2]', 7) |
+------------------------------------------------+
| [1, 6, 7, 2, [3, 4]] |
+------------------------------------------------+
URL: https://mariadb.com/kb/en/json_array_insert/https://mariadb.com/kb/en/json_array_insert/ �
�( ) JSON_CONTAINSJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_CONTAINS(json_doc, val[, path])
Description
-----------
Returns whether or not the specified value is found in the
given JSON document or, optionally, at the specified path
within the document. Returns 1 if it does, 0 if not and NULL
if any of the arguments are null. An error occurs if the
document or path is not valid, or contains the * or **
wildcards.
Examples
--------
SET @json = '{"A": 0, "B": {"C": 1}, "D": 2}';
SELECT JSON_CONTAINS(@json, '2', '$.A');
+----------------------------------+
| JSON_CONTAINS(@json, '2', '$.A') |
+----------------------------------+
| 0 |
+----------------------------------+
SELECT JSON_CONTAINS(@json, '2', '$.D');
+----------------------------------+
| JSON_CONTAINS(@json, '2', '$.D') |
+----------------------------------+
| 1 |
+----------------------------------+
SELECT JSON_CONTAINS(@json, '{"C": 1}', '$.A');
+-----------------------------------------+
| JSON_CONTAINS(@json, '{"C": 1}', '$.A') |
+-----------------------------------------+
| 0 |
+-----------------------------------------+
SELECT JSON_CONTAINS(@json, '{"C": 1}', '$.B');
+-----------------------------------------+
| JSON_CONTAINS(@json, '{"C": 1}', '$.B') |
+-----------------------------------------+
| 1 |
+-----------------------------------------+
URL: https://mariadb.com/kb/en/json_contains/https://mariadb.com/kb/en/json_contains/ � �- ) JSON_CONTAINS_PATHJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_CONTAINS_PATH(json_doc, return_arg, path[, path] ...)
Description
-----------
Indicates whether the given JSON document contains data at
the specified path or paths. Returns 1 if it does, 0 if not
and NULL if any of the arguments are null.
The return_arg can be one or all:
one - Returns 1 if at least one path exists within the JSON
document.
all - Returns 1 only if all paths exist within the JSON
document.
Examples
--------
SET @json = '{"A": 1, "B": [2], "C": [3, 4]}';
SELECT JSON_CONTAINS_PATH(@json, 'one', '$.A', '$.D');
+------------------------------------------------+
| JSON_CONTAINS_PATH(@json, 'one', '$.A', '$.D') |
+------------------------------------------------+
| 1 |
+------------------------------------------------+
1 row in set (0.00 sec)
SELECT JSON_CONTAINS_PATH(@json, 'all', '$.A', '$.D');
+------------------------------------------------+
| JSON_CONTAINS_PATH(@json, 'all', '$.A', '$.D') |
+------------------------------------------------+
| 0 |
+------------------------------------------------+
URL: https://mariadb.com/kb/en/json_contains_path/https://mariadb.com/kb/en/json_contains_path/ �
�% ) JSON_DEPTHJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_DEPTH(json_doc)
Description
-----------
Returns the maximum depth of the given JSON document, or
NULL if the argument is null. An error will occur if the
argument is an invalid JSON document.
Scalar values or empty arrays or objects have a depth of 1.
Arrays or objects that are not empty but contain only
elements or member values of depth 1 will have a depth of 2.
In other cases, the depth will be greater than 2.
Examples
--------
SELECT JSON_DEPTH('[]'), JSON_DEPTH('true'),
JSON_DEPTH('{}');
+------------------+--------------------+------------------+
| JSON_DEPTH('[]') | JSON_DEPTH('true') |
JSON_DEPTH('{}') |
+------------------+--------------------+------------------+
| 1 | 1 | 1 |
+------------------+--------------------+------------------+
SELECT JSON_DEPTH('[1, 2, 3]'), JSON_DEPTH('[[], {},
[]]');
+-------------------------+----------------------------+
| JSON_DEPTH('[1, 2, 3]') | JSON_DEPTH('[[], {}, []]') |
+-------------------------+----------------------------+
| 2 | 2 |
+-------------------------+----------------------------+
SELECT JSON_DEPTH('[1, 2, [3, 4, 5, 6], 7]');
+---------------------------------------+
| JSON_DEPTH('[1, 2, [3, 4, 5, 6], 7]') |
+---------------------------------------+
| 3 |
+---------------------------------------+
URL: https://mariadb.com/kb/en/json_depth/https://mariadb.com/kb/en/json_depth/ ��� ��� � [� �_ � p& ) JSON_EXISTSJSON functions were added in MariaDB 10.2.3.
Syntax
------
Description
-----------
Determines whether a specified JSON value exists in the
given data. Returns 1 if found, 0 if not, or NULL if any of
the inputs were NULL.
Examples
--------
SELECT JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2,
3]}', "$.key2");
+------------------------------------------------------------+
| JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}',
"$.key2") |
+------------------------------------------------------------+
| 1 |
+------------------------------------------------------------+
SELECT JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2,
3]}', "$.key3");
+------------------------------------------------------------+
| JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}',
"$.key3") |
+------------------------------------------------------------+
| 0 |
+------------------------------------------------------------+
SELECT JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2,
3]}', "$.key2[1]");
+---------------------------------------------------------------+
| JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}',
"$.key2[1]") |
+---------------------------------------------------------------+
| 1 |
+---------------------------------------------------------------+
SELECT JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2,
3]}', "$.key2[10]");
+----------------------------------------------------------------+
| JSON_EXISTS('{"key1":"xxxx", "key2":[1, 2, 3]}',
"$.key2[10]") |
+----------------------------------------------------------------+
| 0 |
+----------------------------------------------------------------+
URL: https://mariadb.com/kb/en/json_exists/https://mariadb.com/kb/en/json_exists/ � �' ) JSON_EXTRACTJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_EXTRACT(json_doc, path[, path] ...)
Description
-----------
Extracts data from a JSON document. The extracted data is
selected from the parts matching the path arguments. Returns
all matched values; either as a single matched value, or, if
the arguments could return multiple values, a result
autowrapped as an array in the matching order.
Returns NULL if no paths match or if any of the arguments
are NULL.
An error will occur if any path argument is not a valid
path, or if the json_doc argument is not a valid JSON
document.
Examples
--------
SET @json = '[1, 2, [3, 4]]';
SELECT JSON_EXTRACT(@json, '$[1]');
+-----------------------------+
| JSON_EXTRACT(@json, '$[1]') |
+-----------------------------+
| 2 |
+-----------------------------+
SELECT JSON_EXTRACT(@json, '$[2]');
+-----------------------------+
| JSON_EXTRACT(@json, '$[2]') |
+-----------------------------+
| [3, 4] |
+-----------------------------+
SELECT JSON_EXTRACT(@json, '$[2][1]');
+--------------------------------+
| JSON_EXTRACT(@json, '$[2][1]') |
+--------------------------------+
| 4 |
+--------------------------------+
URL: https://mariadb.com/kb/en/json_extract/https://mariadb.com/kb/en/json_extract/ � L& ) JSON_INSERTJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_INSERT(json_doc, path, val[, path, val] ...)
Description
-----------
Inserts data into a JSON document, returning the resulting
document or NULL if any argument is null.
An error will occur if the JSON document is not invalid, or
if any of the paths are invalid or contain a * or **
wildcard.
JSON_INSERT can only insert data while JSON_REPLACE can only
update. JSON_SET can update or insert data.
Examples
--------
SET @json = '{ "A": 0, "B": [1, 2]}';
SELECT JSON_INSERT(@json, '$.C', '[3, 4]');
+--------------------------------------+
| JSON_INSERT(@json, '$.C', '[3, 4]') |
+--------------------------------------+
| { "A": 0, "B": [1, 2], "C":"[3, 4]"} |
+--------------------------------------+
URL: https://mariadb.com/kb/en/json_insert/https://mariadb.com/kb/en/json_insert/ � �$ ) JSON_KEYSJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_KEYS(json_doc[, path])
Description
-----------
Returns the keys as a JSON array from the top-level value of
a JSON object or, if the optional path argument is provided,
the top-level keys from the path.
Excludes keys from nested sub-objects in the top level
value. The resulting array will be empty if the selected
object is empty.
Returns NULL if any of the arguments are null, a given path
does not locate an object, or if the json_doc argument is
not an object.
An error will occur if JSON document is invalid, the path is
invalid or if the path contains a * or ** wildcard.
Examples
--------
SELECT JSON_KEYS('{"A": 1, "B": {"C": 2}}');
+--------------------------------------+
| JSON_KEYS('{"A": 1, "B": {"C": 2}}') |
+--------------------------------------+
| ["A", "B"] |
+--------------------------------------+
SELECT JSON_KEYS('{"A": 1, "B": 2, "C": {"D":
3}}', '$.C');
+-----------------------------------------------------+
| JSON_KEYS('{"A": 1, "B": 2, "C": {"D": 3}}',
'$.C') |
+-----------------------------------------------------+
| ["D"] |
+-----------------------------------------------------+
URL: https://mariadb.com/kb/en/json_keys/https://mariadb.com/kb/en/json_keys/ k"� ��% ���]� �
� 6& ) JSON_LENGTHJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_LENGTH(json_doc[, path])
Description
-----------
Returns the length of a JSON document, or, if the optional
path argument is given, the length of the value within the
document specified by the path.
Returns NULL if any of the arguments argument are null or
the path argument does not identify a value in the document.
An error will occur if the JSON document is invalid, the
path is invalid or if the path contains a * or ** wildcard.
Length will be determined as follow:
A scalar's length is always 1.
If an array, the number of elements in the array.
If an object, the number of members in the object.
The length of nested arrays or objects are not counted.
Examples
--------
URL: https://mariadb.com/kb/en/json_length/https://mariadb.com/kb/en/json_length/ �
�% ) JSON_MERGEJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_MERGE(json_doc, json_doc[, json_doc] ...)
Description
-----------
Merges the given JSON documents.
Returns the merged result,or NULL if any argument is NULL.
An error occurs if any of the arguments are not valid JSON
documents.
JSON_MERGE has been deprecated since MariaDB 10.2.25,
MariaDB 10.3.16 and MariaDB 10.4.5. JSON_MERGE_PATCH is an
RFC 7396-compliant replacement, and JSON_MERGE_PRESERVE is a
synonym.
Example
SET @json1 = '[1, 2]';
SET @json2 = '[3, 4]';
SELECT JSON_MERGE(@json1,@json2);
+---------------------------+
| JSON_MERGE(@json1,@json2) |
+---------------------------+
| [1, 2, 3, 4] |
+---------------------------+
URL: https://mariadb.com/kb/en/json_merge/https://mariadb.com/kb/en/json_merge/ � �+ ) JSON_MERGE_PATCHJSON_MERGE_PATCH was introduced in MariaDB 10.2.25, MariaDB
10.3.16 and MariaDB 10.4.5.
Syntax
------
JSON_MERGE_PATCH(json_doc, json_doc[, json_doc] ...)
Description
-----------
Merges the given JSON documents, returning the merged
result, or NULL if any argument is NULL.
JSON_MERGE_PATCH is an RFC 7396-compliant replacement for
JSON_MERGE, which has been deprecated.
Example
SET @json1 = '[1, 2]';
SET @json2 = '[2, 3]';
SELECT
JSON_MERGE_PATCH(@json1,@json2),JSON_MERGE_PRESERVE(@json1,@json2);
+---------------------------------+------------------------------------+
| JSON_MERGE_PATCH(@json1,@json2) |
JSON_MERGE_PRESERVE(@json1,@json2) |
+---------------------------------+------------------------------------+
| [2, 3] | [1, 2, 2, 3] |
+---------------------------------+------------------------------------+
URL: https://mariadb.com/kb/en/json_merge_patch/https://mariadb.com/kb/en/json_merge_patch/ � �. ) JSON_MERGE_PRESERVEJSON_MERGE_PRESERVE was introduced in MariaDB 10.2.25,
MariaDB 10.3.16 and MariaDB 10.4.5.
Syntax
------
JSON_MERGE_PRESERVE(json_doc, json_doc[, json_doc] ...)
Description
-----------
Merges the given JSON documents, returning the merged
result, or NULL if any argument is NULL.
JSON_MERGE_PRESERVE was introduced in MariaDB 10.2.25,
MariaDB 10.3.16 and MariaDB 10.4.5 as a synonym for
JSON_MERGE, which has been deprecated.
Example
SET @json1 = '[1, 2]';
SET @json2 = '[2, 3]';
SELECT
JSON_MERGE_PATCH(@json1,@json2),JSON_MERGE_PRESERVE(@json1,@json2);
+---------------------------------+------------------------------------+
| JSON_MERGE_PATCH(@json1,@json2) |
JSON_MERGE_PRESERVE(@json1,@json2) |
+---------------------------------+------------------------------------+
| [2, 3] | [1, 2, 2, 3] |
+---------------------------------+------------------------------------+
URL: https://mariadb.com/kb/en/json_merge_preserve/https://mariadb.com/kb/en/json_merge_preserve/ �
�% ) JSON_QUERYJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_QUERY(json_doc, path)
Description
-----------
Given a JSON document, returns an object or array specified
by the path. Returns NULL if not given a valid JSON
document, or if there is no match.
Examples
--------
select json_query('{"key1":{"a":1, "b":[1,2]}}',
'$.key1');
+-----------------------------------------------------+
| json_query('{"key1":{"a":1, "b":[1,2]}}',
'$.key1') |
+-----------------------------------------------------+
| {"a":1, "b":[1,2]} |
+-----------------------------------------------------+
select json_query('{"key1":123, "key1": [1,2,3]}',
'$.key1');
+-------------------------------------------------------+
| json_query('{"key1":123, "key1": [1,2,3]}',
'$.key1') |
+-------------------------------------------------------+
| [1,2,3] |
+-------------------------------------------------------+
URL: https://mariadb.com/kb/en/json_query/https://mariadb.com/kb/en/json_query/ �
% ) JSON_QUOTEJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_QUOTE(json_value)
Description
-----------
Quotes a string as a JSON value, usually for producing valid
JSON string literals for inclusion in JSON documents. Wraps
the string with double quote characters and escapes interior
quotes and other special characters, returning a utf8mb4
string.
Returns NULL if the argument is NULL.
Examples
--------
SELECT JSON_QUOTE('A'), JSON_QUOTE("B"),
JSON_QUOTE('"C"');
+-----------------+-----------------+-------------------+
| JSON_QUOTE('A') | JSON_QUOTE("B") |
JSON_QUOTE('"C"') |
+-----------------+-----------------+-------------------+
| "A" | "B" | "\"C\"" |
+-----------------+-----------------+-------------------+
URL: https://mariadb.com/kb/en/json_quote/https://mariadb.com/kb/en/json_quote/ �Z���
����; u�� �. � �& ) JSON_REMOVEJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_REMOVE(json_doc, path[, path] ...)
Description
-----------
Removes data from a JSON document returning the result, or
NULL if any of the arguments are null. If the element does
not exist in the document, no changes are made.
An error will occur if JSON document is invalid, the path is
invalid or if the path contains a * or ** wildcard.
Path arguments are evaluated from left to right, with the
result from the earlier evaluation being used as the value
for the next.
Examples
--------
SELECT JSON_REMOVE('{"A": 1, "B": 2, "C": {"D":
3}}', '$.C');
+-------------------------------------------------------+
| JSON_REMOVE('{"A": 1, "B": 2, "C": {"D": 3}}',
'$.C') |
+-------------------------------------------------------+
| {"A": 1, "B": 2} |
+-------------------------------------------------------+
SELECT JSON_REMOVE('["A", "B", ["C", "D"],
"E"]', '$[1]');
+----------------------------------------------------+
| JSON_REMOVE('["A", "B", ["C", "D"], "E"]',
'$[1]') |
+----------------------------------------------------+
| ["A", ["C", "D"], "E"] |
+----------------------------------------------------+
URL: https://mariadb.com/kb/en/json_remove/https://mariadb.com/kb/en/json_remove/ � �' ) JSON_REPLACEJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_REPLACE(json_doc, path, val[, path, val] ...)
Description
-----------
Replaces existing values in a JSON document, returning the
result, or NULL if any of the arguments are NULL.
An error will occur if the JSON document is invalid, the
path is invalid or if the path contains a * or ** wildcard.
Paths and values are evaluated from left to right, with the
result from the earlier evaluation being used as the value
for the next.
JSON_REPLACE can only update data, while JSON_INSERT can
only insert. JSON_SET can update or insert data.
Examples
--------
SELECT JSON_REPLACE('{ "A": 1, "B": [2, 3]}',
'$.B[1]', 4);
+-----------------------------------------------------+
| JSON_REPLACE('{ "A": 1, "B": [2, 3]}', '$.B[1]',
4) |
+-----------------------------------------------------+
| { "A": 1, "B": [2, 4]} |
+-----------------------------------------------------+
URL: https://mariadb.com/kb/en/json_replace/https://mariadb.com/kb/en/json_replace/ � �& ) JSON_SEARCHJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_SEARCH(json_doc, return_arg, search_str[, escape_char[,
path] ...])
Description
-----------
Returns the path to the given string within a JSON document,
or NULL if any of json_doc, search_str or a path argument is
NULL; if the search string is not found, or if no path
exists within the document.
A warning will occur if the JSON document is not valid, any
of the path arguments are not valid, if return_arg is
neither one nor all, or if the escape character is not a
constant. NULL will be returned.
return_arg can be one of two values:
'one: Terminates after finding the first match, so will
return one path string. If there is more than one match, it
is undefined which is considered first.
all: Returns all matching path strings, without duplicates.
Multiple strings are autowrapped as an array. The order is
undefined.
Examples
--------
SET @json = '["A", [{"B": "1"}], {"C":"AB"},
{"D":"BC"}]';
SELECT JSON_SEARCH(@json, 'one', 'AB');
+---------------------------------+
| JSON_SEARCH(@json, 'one', 'AB') |
+---------------------------------+
| "$[2].C" |
+---------------------------------+
URL: https://mariadb.com/kb/en/json_search/https://mariadb.com/kb/en/json_search/ � $ ) JSON_TYPEJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_TYPE(json_val)
Description
-----------
Returns the type of a JSON value, or NULL if the argument is
null.
An error will occur if the argument is an invalid JSON
value.
The following is a complete list of the possible return
types:
Return type | Value |
ARRAY | JSON array |
BIT | MariaDB BIT scalar |
BLOB | MariaDB binary types (BINARY, VARBINARY or BLOB) |
BOOLEAN | JSON true/false literals |
DATE | MariaDB DATE scalar |
DATETIME | MariaDB DATETIME or TIMESTAMP scalar |
DECIMAL | MariaDB DECIMAL or NUMERIC scalar |
DOUBLE | MariaDB DOUBLE FLOAT scalar |
INTEGER | MariaDB integer types (TINYINT, SMALLINT,
MEDIUMINT, INT or BIGINT) |
NULL | JSON null literal or NULL argument |
OBJECT | JSON object |
OPAQUE | Any valid JSON value that is not one of the other
types. |
STRING | MariaDB character types (CHAR, VARCHAR, TEXT, ENUM
or SET) |
TIME | MariaDB TIME scalar |
Examples
--------
SELECT JSON_TYPE('{"A": 1, "B": 2, "C": 3}');
+---------------------------------------+
| JSON_TYPE('{"A": 1, "B": 2, "C": 3}') |
+---------------------------------------+
| OBJECT |
+---------------------------------------+
URL: https://mariadb.com/kb/en/json_type/https://mariadb.com/kb/en/json_type/ qM[ +0 �|ǵ ��
� �' ) JSON_UNQUOTEJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_UNQUOTE(val)
Description
-----------
Unquotes a JSON value, returning a string, or NULL if the
argument is null.
An error will occur if the given value begins and ends with
double quotes and is an invalid JSON string literal.
Certain character sequences have special meanings within a
string. Usually, a backspace is ignored, but the escape
sequences in the table below are recognised by MariaDB,
unless the SQL Mode is set to NO_BACKSLASH_ESCAPES SQL.
Escape sequence | Character |
\" | Double quote (") |
\b | Backspace |
\f | Formfeed |
\n | Newline (linefeed) |
\r | Carriage return |
\t | Tab |
\\ | Backslash (\) |
\uXXXX | UTF-8 bytes for Unicode value XXXX |
Examples
--------
SELECT JSON_UNQUOTE('"Monty"');
+-------------------------+
| JSON_UNQUOTE('"Monty"') |
+-------------------------+
| Monty |
+-------------------------+
With the default SQL Mode:
SELECT JSON_UNQUOTE('Si\bng\ting');
+-----------------------------+
| JSON_UNQUOTE('Si\bng\ting') |
+-----------------------------+
| Sng ing |
+-----------------------------+
Setting NO_BACKSLASH_ESCAPES:
SET @@sql_mode = 'NO_BACKSLASH_ESCAPES';
SELECT JSON_UNQUOTE('Si\bng\ting');
+-----------------------------+
| JSON_UNQUOTE('Si\bng\ting') |
+-----------------------------+
| Si\bng\ting |
+-----------------------------+
URL: https://mariadb.com/kb/en/json_unquote/https://mariadb.com/kb/en/json_unquote/ �
% ) JSON_VALIDJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_VALID(value)
Description
-----------
Indicates whether the given value is a valid JSON document
or not. Returns 1 if valid, 0 if not, and NULL if the
argument is NULL.
From MariaDB 10.4.3, the JSON_VALID function is
automatically used as a CHECK constraint for the JSON data
type alias in order to ensure that a valid json document is
inserted.
Examples
--------
SELECT JSON_VALID('{"id": 1, "name": "Monty"}');
+------------------------------------------+
| JSON_VALID('{"id": 1, "name": "Monty"}') |
+------------------------------------------+
| 1 |
+------------------------------------------+
SELECT JSON_VALID('{"id": 1, "name": "Monty",
"oddfield"}');
+------------------------------------------------------+
| JSON_VALID('{"id": 1, "name": "Monty",
"oddfield"}') |
+------------------------------------------------------+
| 0 |
+------------------------------------------------------+
URL: https://mariadb.com/kb/en/json_valid/https://mariadb.com/kb/en/json_valid/ �
Y% ) JSON_VALUEJSON functions were added in MariaDB 10.2.3.
Syntax
------
JSON_VALUE(json_doc, path)
Description
-----------
Given a JSON document, returns the scalar specified by the
path. Returns NULL if not given a valid JSON document, or if
there is no match.
Examples
--------
select json_value('{"key1":123}', '$.key1');
+--------------------------------------+
| json_value('{"key1":123}', '$.key1') |
+--------------------------------------+
| 123 |
+--------------------------------------+
select json_value('{"key1": [1,2,3], "key1":123}',
'$.key1');
+-------------------------------------------------------+
| json_value('{"key1": [1,2,3], "key1":123}',
'$.key1') |
+-------------------------------------------------------+
| 123 |
+-------------------------------------------------------+
URL: https://mariadb.com/kb/en/json_value/https://mariadb.com/kb/en/json_value/ �
�% * DENSE_RANKThe DENSE_RANK() function was first introduced with window
functions in MariaDB 10.2.0.
Syntax
------
DENSE_RANK() OVER (
[ PARTITION BY partition_expression ]
[ ORDER BY order_list ]
)
Description
-----------
DENSE_RANK() is a window function that displays the number
of a given row, starting at one and following the ORDER BY
sequence of the window function, with identical values
receiving the same result. Unlike the RANK() function, there
are no skipped values if the preceding results are
identical. It is also similar to the ROW_NUMBER() function
except that in that function, identical values will receive
a different row number for each result.
Examples
--------
The distinction between DENSE_RANK(), RANK() and
ROW_NUMBER():
CREATE TABLE student(course VARCHAR(10), mark int, name
varchar(10));
INSERT INTO student VALUES
('Maths', 60, 'Thulile'),
('Maths', 60, 'Pritha'),
('Maths', 70, 'Voitto'),
('Maths', 55, 'Chun'),
('Biology', 60, 'Bilal'),
('Biology', 70, 'Roger');
SELECT
RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS
rank,
DENSE_RANK() OVER (PARTITION BY course ORDER BY mark DESC)
AS dense_rank,
ROW_NUMBER() OVER (PARTITION BY course ORDER BY mark DESC)
AS row_num,
course, mark, name
FROM student ORDER BY course, mark DESC;
+------+------------+---------+---------+------+---------+
| rank | dense_rank | row_num | course | mark | name |
+------+------------+---------+---------+------+---------+
| 1 | 1 | 1 | Biology | 70 | Roger |
| 2 | 2 | 2 | Biology | 60 | Bilal |
| 1 | 1 | 1 | Maths | 70 | Voitto |
| 2 | 2 | 2 | Maths | 60 | Thulile |
| 2 | 2 | 3 | Maths | 60 | Pritha |
| 4 | 3 | 4 | Maths | 55 | Chun |
+------+------------+---------+---------+------+---------+
URL: https://mariadb.com/kb/en/dense_rank/https://mariadb.com/kb/en/dense_rank/ �
9O
� D �WV}� � � � < * Window Functions OverviewWindow functions were introduced in MariaDB 10.2.
Introduction
Window functions allow calculations to be performed across a
set of rows related to the current row.
Syntax
------
function (expression) OVER (
[ PARTITION BY expression_list ]
[ ORDER BY order_list [ frame_clause ] ] )
function:
A valid window function
expression_list:
expression | column_name [, expr_list ]
order_list:
expression | column_name [ ASC | DESC ]
[, ... ]
frame_clause:
{ROWS | RANGE} {frame_border | BETWEEN frame_border AND
frame_border}
frame_border:
| UNBOUNDED PRECEDING
| UNBOUNDED FOLLOWING
| CURRENT ROW
| expr PRECEDING
| expr FOLLOWING
Description
-----------
In some ways, window functions are similar to aggregate
functions in that they perform calculations across a set of
rows. However, unlike aggregate functions, the output is not
grouped into a single row.
Non-aggregate window functions include
CUME_DIST
DENSE_RANK
FIRST_VALUE
LAG
LAST_VALUE
LEAD
MEDIAN
NTH_VALUE
NTILE
PERCENT_RANK
PERCENTILE_CONT
PERCENTILE_DISC
RANK, ROW_NUMBER
Aggregate functions that can also be used as window
functions include
AVG
BIT_AND
BIT_OR
BIT_XOR
COUNT
MAX
MIN
STD
STDDEV
STDDEV_POP
STDDEV_SAMP
SUM
VAR_POP
VAR_SAMP
VARIANCE
Window function queries are characterised by the OVER
keyword, following which the set of rows used for the
calculation is specified. By default, the set of rows used
for the calculation (the "window) is the entire dataset,
which can be ordered with the ORDER BY clause. The PARTITION
BY clause is used to reduce the window to a particular group
within the dataset.
For example, given the following data:
CREATE TABLE student (name CHAR(10), test CHAR(10), score
TINYINT);
INSERT INTO student VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87), ('Tatiana', 'Tuning', 83);
the following two queries return the average partitioned by
test and by name respectively:
SELECT name, test, score, AVG(score) OVER (PARTITION BY
test)
AS average_by_test FROM student;
+---------+--------+-------+-----------------+
| name | test | score | average_by_test |
+---------+--------+-------+-----------------+
| Chun | SQL | 75 | 65.2500 |
| Chun | Tuning | 73 | 68.7500 |
| Esben | SQL | 43 | 65.2500 |
| Esben | Tuning | 31 | 68.7500 |
| Kaolin | SQL | 56 | 65.2500 |
| Kaolin | Tuning | 88 | 68.7500 |
| Tatiana | SQL | 87 | 65.2500 |
| Tatiana | Tuning | 83 | 68.7500 |
+---------+--------+-------+-----------------+
SELECT name, test, score, AVG(score) OVER (PARTITION BY
name)
AS average_by_name FROM student;
+---------+--------+-------+-----------------+
| name | test | score | average_by_name |
+---------+--------+-------+-----------------+
| Chun | SQL | 75 | 74.0000 |
| Chun | Tuning | 73 | 74.0000 |
| Esben | SQL | 43 | 37.0000 |
| Esben | Tuning | 31 | 37.0000 |
| Kaolin | SQL | 56 | 72.0000 |
| Kaolin | Tuning | 88 | 72.0000 |
| Tatiana | SQL | 87 | 85.0000 |
| Tatiana | Tuning | 83 | 85.0000 |
+---------+--------+-------+-----------------+
It is also possible to specify which rows to include for the
window function (for example, the current row and all
preceding rows). See Window Frames for more details.
Scope
Window functions were introduced in SQL:2003, and their
definition was expanded in subsequent versions of the
standard. The last expansion was in the latest version of
the standard, SQL:2011.
Most database products support a subset of the standard,
they implement some functions defined as late as in
SQL:2011, and at the same time leave some parts of SQL:2008
unimplemented.
MariaDB:
Supports ROWS and RANGE-type frames
All kinds of frame bounds are supported, including RANGE
PRECEDING|FOLLOWING n frame bounds (unlike PostgreSQL or MS
SQL Server)
Does not yet support DATE[TIME] datatype and arithmetic for
RANGE-type frames (MDEV-9727)
Does not support GROUPS-type frames (it seems that no
popular database supports it, either)
Does not support frame exclusion (no other database seems to
support it, either) (MDEV-9724)
Does not support explicit NULLS FIRST or NULLS LAST.
Does not support nested navigation in window functions (this
is VALUE_OF(expr AT row_marker [, default_value) syntax)
The following window functions are supported:
"Streamable" window functions: ROW_NUMBER, RANK,
DENSE_RANK,
Window functions that can be streamed once the number of
rows in partition is known: PERCENT_RANK, CUME_DIST, NTILE
Aggregate functions that are currently supported as window
functions are: COUNT, SUM, AVG, BIT_OR, BIT_AND, BIT_XOR.
Aggregate functions with the DISTINCT specifier (e.g. COUNT(
DISTINCT x)) are not supported as window functions.
Links
MDEV-6115 is the main jira task for window functions
development. Other tasks are are attached as sub-tasks
bb-10.2-mdev9543 is the feature tree for window functions.
Development is ongoing, and this tree has the newest
changes.
Testcases are in mysql-test/t/win*.test
Examples
--------
Given the following sample data:
CREATE TABLE users (
email VARCHAR(30),
first_name VARCHAR(30),
last_name VARCHAR(30),
account_type VARCHAR(30)
);
INSERT INTO users VALUES
('admin@boss.org', 'Admin', 'Boss', 'admin'),
('bob.carlsen@foo.bar', 'Bob', 'Carlsen',
'regular'),
('eddie.stevens@data.org', 'Eddie', 'Stevens',
'regular'),
('john.smith@xyz.org', 'John', 'Smith', 'regular'),
('root@boss.org', 'Root', 'Chief', 'admin')
First, let's order the records by email alphabetically,
giving each an ascending rnum value starting with 1. This
will make use of the ROW_NUMBER window function:
SELECT row_number() OVER (ORDER BY email) AS rnum,
email, first_name, last_name, account_type
FROM users ORDER BY email;
+------+------------------------+------------+-----------+--------------+
| rnum | email | first_name | last_name | account_type |
+------+------------------------+------------+-----------+--------------+
| 1 | admin@boss.org | Admin | Boss | admin |
| 2 | bob.carlsen@foo.bar | Bob | Carlsen | regular |
| 3 | eddie.stevens@data.org | Eddie | Stevens | regular |
| 4 | john.smith@xyz.org | John | Smith | regular |
| 5 | root@boss.org | Root | Chief | admin |
+------+------------------------+------------+-----------+--------------
We can generate separate sequences based on account type,
using the PARTITION BY clause:
SELECT row_number() OVER (PARTITION BY account_type ORDER BY
email) AS rnum,
email, first_name, last_name, account_type
FROM users ORDER BY account_type,email;
+------+------------------------+------------+-----------+--------------+
| rnum | email | first_name | last_name | account_type |
+------+------------------------+------------+-----------+--------------+
| 1 | admin@boss.org | Admin | Boss | admin |
| 2 | root@boss.org | Root | Chief | admin |
| 1 | bob.carlsen@foo.bar | Bob | Carlsen | regular |
| 2 | eddie.stevens@data.org | Eddie | Stevens | regular |
| 3 | john.smith@xyz.org | John | Smith | regular |
+------+------------------------+------------+-----------+--------------+
Given the following structure and data, we want to find the
top 5 salaries from each department.
CREATE TABLE employee_salaries (dept VARCHAR(20), name
VARCHAR(20), salary INT(11));
INSERT INTO employee_salaries VALUES
('Engineering', 'Dharma', 3500),
('Engineering', 'Bình', 3000),
('Engineering', 'Adalynn', 2800),
('Engineering', 'Samuel', 2500),
('Engineering', 'Cveta', 2200),
('Engineering', 'Ebele', 1800),
('Sales', 'Carbry', 500),
('Sales', 'Clytemnestra', 400),
('Sales', 'Juraj', 300),
('Sales', 'Kalpana', 300),
('Sales', 'Svantepolk', 250),
('Sales', 'Angelo', 200);
We could do this without using window functions, as follows:
select dept, name, salary
from employee_salaries as t1
where (select count(t2.salary)
from employee_salaries as t2
where t1.name != t2.name and
t1.dept = t2.dept and
t2.salary > t1.salary)
URL:
https://mariadb.com/kb/en/library/window-functions-overview/https://mariadb.com/kb/en/library/window-functions-overview/ � t��p �J �
W0 * Window FramesWindow functions were first introduced in MariaDB 10.2.0.
Syntax
------
frame_clause:
{ROWS | RANGE} {frame_border | BETWEEN frame_border AND
frame_border}
frame_border:
| UNBOUNDED PRECEDING
| UNBOUNDED FOLLOWING
| CURRENT ROW
| expr PRECEDING
| expr FOLLOWING
Description
-----------
A basic overview of window functions is described in Window
Functions Overview. Window frames expand this functionality
by allowing the function to include a specified a number of
rows around the current row.
These include:
All rows before the current row (UNBOUNDED PRECEDING), for
example RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
All rows after the current row (UNBOUNDED FOLLOWING), for
example RANGE BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING
A set number of rows before the current row (expr PRECEDING)
for example RANGE BETWEEN 6 PRECEDING AND CURRENT ROW
A set number of rows after the current row (expr PRECEDING
AND expr FOLLOWING) for example RANGE BETWEEN CURRENT ROW
AND 2 FOLLOWING
A specified number of rows both before and after the current
row, for example RANGE BETWEEN 6 PRECEDING AND 3 FOLLOWING
The following functions operate on window frames:
AVG
BIT_AND
BIT_OR
BIT_XOR
COUNT
LEAD
MAX
MIN
NTILE
STD
STDDEV
STDDEV_POP
STDDEV_SAMP
SUM
VAR_POP
VAR_SAMP
VARIANCE
Window frames are determined by the frame_clause in the
window function request.
Take the following example:
CREATE TABLE `student_test` (
name char(10),
test char(10),
score tinyint(4)
);
INSERT INTO student_test VALUES
('Chun', 'SQL', 75), ('Chun', 'Tuning', 73),
('Esben', 'SQL', 43), ('Esben', 'Tuning', 31),
('Kaolin', 'SQL', 56), ('Kaolin', 'Tuning', 88),
('Tatiana', 'SQL', 87);
SELECT name, test, score, SUM(score)
OVER () AS total_score
FROM student_test;
+---------+--------+-------+-------------+
| name | test | score | total_score |
+---------+--------+-------+-------------+
| Chun | SQL | 75 | 453 |
| Chun | Tuning | 73 | 453 |
| Esben | SQL | 43 | 453 |
| Esben | Tuning | 31 | 453 |
| Kaolin | SQL | 56 | 453 |
| Kaolin | Tuning | 88 | 453 |
| Tatiana | SQL | 87 | 453 |
+---------+--------+-------+-------------+
By not specifying an OVER condition, the SUM function is run
over the entire dataset. However, if we specify an ORDER BY
condition based on score (and order the entire result in the
same way for clarity), the following result is returned:
SELECT name, test, score, SUM(score)
OVER (ORDER BY score) AS total_score
FROM student_test ORDER BY score;
+---------+--------+-------+-------------+
| name | test | score | total_score |
+---------+--------+-------+-------------+
| Esben | Tuning | 31 | 31 |
| Esben | SQL | 43 | 74 |
| Kaolin | SQL | 56 | 130 |
| Chun | Tuning | 73 | 203 |
| Chun | SQL | 75 | 278 |
| Tatiana | SQL | 87 | 365 |
| Kaolin | Tuning | 88 | 453 |
+---------+--------+-------+-------------+
The total_score column represents a running total of the
current row, and all previous rows. The window frame in this
example expands as the function proceeds.
The above query makes use of the default to define the
window frame. It could be written explicitly as follows:
SELECT name, test, score, SUM(score)
OVER (ORDER BY score RANGE BETWEEN UNBOUNDED PRECEDING AND
CURRENT ROW) AS total_score
FROM student_test ORDER BY score;
+---------+--------+-------+-------------+
| name | test | score | total_score |
+---------+--------+-------+-------------+
| Esben | Tuning | 31 | 31 |
| Esben | SQL | 43 | 74 |
| Kaolin | SQL | 56 | 130 |
| Chun | Tuning | 73 | 203 |
| Chun | SQL | 75 | 278 |
| Tatiana | SQL | 87 | 365 |
| Kaolin | Tuning | 88 | 453 |
+---------+--------+-------+-------------+
Let's look at some alternatives:
Firstly, applying the window function to the current row and
all following rows can be done with the use of UNBOUNDED
FOLLOWING:
SELECT name, test, score, SUM(score)
OVER (ORDER BY score RANGE BETWEEN CURRENT ROW AND
UNBOUNDED FOLLOWING) AS total_score
FROM student_test ORDER BY score;
+---------+--------+-------+-------------+
| name | test | score | total_score |
+---------+--------+-------+-------------+
| Esben | Tuning | 31 | 453 |
| Esben | SQL | 43 | 422 |
| Kaolin | SQL | 56 | 379 |
| Chun | Tuning | 73 | 323 |
| Chun | SQL | 75 | 250 |
| Tatiana | SQL | 87 | 175 |
| Kaolin | Tuning | 88 | 88 |
+---------+--------+-------+-------------+
It's possible to specify a number of rows, rather than the
entire unbounded following or preceding set. The following
example takes the current row, as well as the previous row:
SELECT name, test, score, SUM(score)
OVER (ORDER BY score ROWS BETWEEN 1 PRECEDING AND CURRENT
ROW) AS total_score
FROM student_test ORDER BY score;
+---------+--------+-------+-------------+
| name | test | score | total_score |
+---------+--------+-------+-------------+
| Esben | Tuning | 31 | 31 |
| Esben | SQL | 43 | 74 |
| Kaolin | SQL | 56 | 99 |
| Chun | Tuning | 73 | 129 |
| Chun | SQL | 75 | 148 |
| Tatiana | SQL | 87 | 162 |
| Kaolin | Tuning | 88 | 175 |
+---------+--------+-------+-------------+
The current row and the following row:
SELECT name, test, score, SUM(score)
OVER (ORDER BY score ROWS BETWEEN 1 PRECEDING AND 1
FOLLOWING) AS total_score
FROM student_test ORDER BY score;
+---------+--------+-------+-------------+
| name | test | score | total_score |
+---------+--------+-------+-------------+
| Esben | Tuning | 31 | 74 |
| Esben | SQL | 43 | 130 |
| Kaolin | SQL | 56 | 172 |
| Chun | Tuning | 73 | 204 |
| Chun | SQL | 75 | 235 |
| Tatiana | SQL | 87 | 250 |
| Kaolin | Tuning | 88 | 175 |
+---------+--------+-------+-------------+
URL: https://mariadb.com/kb/en/library/window-frames/https://mariadb.com/kb/en/library/window-frames/ ��Z�� �4 � & * FIRST_VALUEThe FIRST_VALUE() function was first introduced with other
window functions in MariaDB 10.2.
Syntax
------
FIRST_VALUE(expr) OVER (
[ PARTITION BY partition_expression ]
[ ORDER BY order_list ]
)
Description
-----------
FIRST_VALUE returns the first result from an ordered set, or
NULL if no such result exists.
Examples
--------
CREATE TABLE t1 (
pk int primary key,
a int,
b int,
c char(10),
d decimal(10, 3),
e real
);
INSERT INTO t1 VALUES
( 1, 0, 1, 'one', 0.1, 0.001),
( 2, 0, 2, 'two', 0.2, 0.002),
( 3, 0, 3, 'three', 0.3, 0.003),
( 4, 1, 2, 'three', 0.4, 0.004),
( 5, 1, 1, 'two', 0.5, 0.005),
( 6, 1, 1, 'one', 0.6, 0.006),
( 7, 2, NULL, 'n_one', 0.5, 0.007),
( 8, 2, 1, 'n_two', NULL, 0.008),
( 9, 2, 2, NULL, 0.7, 0.009),
(10, 2, 0, 'n_four', 0.8, 0.010),
(11, 2, 10, NULL, 0.9, NULL);
SELECT pk, FIRST_VALUE(pk) OVER (ORDER BY pk) AS first_asc,
LAST_VALUE(pk) OVER (ORDER BY pk) AS last_asc,
FIRST_VALUE(pk) OVER (ORDER BY pk DESC) AS first_desc,
LAST_VALUE(pk) OVER (ORDER BY pk DESC) AS last_desc
FROM t1
ORDER BY pk DESC;
+----+-----------+----------+------------+-----------+
| pk | first_asc | last_asc | first_desc | last_desc |
+----+-----------+----------+------------+-----------+
| 11 | 1 | 11 | 11 | 11 |
| 10 | 1 | 10 | 11 | 10 |
| 9 | 1 | 9 | 11 | 9 |
| 8 | 1 | 8 | 11 | 8 |
| 7 | 1 | 7 | 11 | 7 |
| 6 | 1 | 6 | 11 | 6 |
| 5 | 1 | 5 | 11 | 5 |
| 4 | 1 | 4 | 11 | 4 |
| 3 | 1 | 3 | 11 | 3 |
| 2 | 1 | 2 | 11 | 2 |
| 1 | 1 | 1 | 11 | 1 |
+----+-----------+----------+------------+-----------+
CREATE OR REPLACE TABLE t1 (i int);
INSERT INTO t1 VALUES
(1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
SELECT i,
FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW
and 1 FOLLOWING) AS f_1f,
LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW and
1 FOLLOWING) AS l_1f,
FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING
AND 1 FOLLOWING) AS f_1p1f,
LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 PRECEDING AND
1 FOLLOWING) AS f_1p1f,
FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING
AND 1 PRECEDING) AS f_2p1p,
LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 2 PRECEDING AND
1 PRECEDING) AS f_2p1p,
FIRST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING
AND 2 FOLLOWING) AS f_1f2f,
LAST_VALUE(i) OVER (ORDER BY i ROWS BETWEEN 1 FOLLOWING AND
2 FOLLOWING) AS f_1f2f
FROM t1;
+------+------+------+--------+--------+--------+--------+--------+--------+
| i | f_1f | l_1f | f_1p1f | f_1p1f | f_2p1p | f_2p1p |
f_1f2f | f_1f2f |
+------+------+------+--------+--------+--------+--------+--------+--------+
| 1 | 1 | 2 | 1 | 2 | NULL | NULL | 2 | 3 |
| 2 | 2 | 3 | 1 | 3 | 1 | 1 | 3 | 4 |
| 3 | 3 | 4 | 2 | 4 | 1 | 2 | 4 | 5 |
| 4 | 4 | 5 | 3 | 5 | 2 | 3 | 5 | 6 |
| 5 | 5 | 6 | 4 | 6 | 3 | 4 | 6 | 7 |
| 6 | 6 | 7 | 5 | 7 | 4 | 5 | 7 | 8 |
| 7 | 7 | 8 | 6 | 8 | 5 | 6 | 8 | 9 |
| 8 | 8 | 9 | 7 | 9 | 6 | 7 | 9 | 10 |
| 9 | 9 | 10 | 8 | 10 | 7 | 8 | 10 | 10 |
| 10 | 10 | 10 | 9 | 10 | 8 | 9 | NULL | NULL |
+------+------+------+--------+--------+--------+--------+--------+--------+
URL: https://mariadb.com/kb/en/first_value/https://mariadb.com/kb/en/first_value/ � ) * LAGThe LAG() function was first introduced with other window
functions in MariaDB 10.2.
Syntax
------
LAG (expr[, offset]) OVER (
[ PARTITION BY partition_expression ]
< ORDER BY order_list >
)
Description
-----------
The LAG function accesses data from a previous row according
to the ORDER BY clause without the need for a self-join. The
specific row is determined by the offset (default 1), which
specifies the number of rows behind the current row to use.
An offset of 0 is the current row.
Examples
--------
CREATE TABLE t1 (pk int primary key, a int, b int, c
char(10), d decimal(10, 3), e real);
INSERT INTO t1 VALUES
( 1, 0, 1, 'one', 0.1, 0.001),
( 2, 0, 2, 'two', 0.2, 0.002),
( 3, 0, 3, 'three', 0.3, 0.003),
( 4, 1, 2, 'three', 0.4, 0.004),
( 5, 1, 1, 'two', 0.5, 0.005),
( 6, 1, 1, 'one', 0.6, 0.006),
( 7, 2, NULL, 'n_one', 0.5, 0.007),
( 8, 2, 1, 'n_two', NULL, 0.008),
( 9, 2, 2, NULL, 0.7, 0.009),
(10, 2, 0, 'n_four', 0.8, 0.010),
(11, 2, 10, NULL, 0.9, NULL);
SELECT pk, LAG(pk) OVER (ORDER BY pk) AS l,
LAG(pk,1) OVER (ORDER BY pk) AS l1,
LAG(pk,2) OVER (ORDER BY pk) AS l2,
LAG(pk,0) OVER (ORDER BY pk) AS l0,
LAG(pk,-1) OVER (ORDER BY pk) AS lm1,
LAG(pk,-2) OVER (ORDER BY pk) AS lm2
FROM t1;
+----+------+------+------+------+------+------+
| pk | l | l1 | l2 | l0 | lm1 | lm2 |
+----+------+------+------+------+------+------+
| 1 | NULL | NULL | NULL | 1 | 2 | 3 |
| 2 | 1 | 1 | NULL | 2 | 3 | 4 |
| 3 | 2 | 2 | 1 | 3 | 4 | 5 |
| 4 | 3 | 3 | 2 | 4 | 5 | 6 |
| 5 | 4 | 4 | 3 | 5 | 6 | 7 |
| 6 | 5 | 5 | 4 | 6 | 7 | 8 |
| 7 | 6 | 6 | 5 | 7 | 8 | 9 |
| 8 | 7 | 7 | 6 | 8 | 9 | 10 |
| 9 | 8 | 8 | 7 | 9 | 10 | 11 |
| 10 | 9 | 9 | 8 | 10 | 11 | NULL |
| 11 | 10 | 10 | 9 | 11 | NULL | NULL |
+----+------+------+------+------+------+------+
URL: https://mariadb.com/kb/en/lag/https://mariadb.com/kb/en/lag/ h X \ RM�^ �W � ! * LEADThe LEAD() function was first introduced with other window
functions in MariaDB 10.2.
Syntax
------
LEAD (expr[, offset]) OVER (
[ PARTITION BY partition_expression ]
[ ORDER BY order_list ]
)
Description
-----------
The LEAD function accesses data from a following row in the
same result set without the need for a self-join. The
specific row is determined by the offset (default 1), which
specifies the number of rows ahead the current row to use.
An offset of 0 is the current row.
Example
CREATE TABLE t1 (pk int primary key, a int, b int, c
char(10), d decimal(10, 3), e real);
INSERT INTO t1 VALUES
( 1, 0, 1, 'one', 0.1, 0.001),
( 2, 0, 2, 'two', 0.2, 0.002),
( 3, 0, 3, 'three', 0.3, 0.003),
( 4, 1, 2, 'three', 0.4, 0.004),
( 5, 1, 1, 'two', 0.5, 0.005),
( 6, 1, 1, 'one', 0.6, 0.006),
( 7, 2, NULL, 'n_one', 0.5, 0.007),
( 8, 2, 1, 'n_two', NULL, 0.008),
( 9, 2, 2, NULL, 0.7, 0.009),
(10, 2, 0, 'n_four', 0.8, 0.010),
(11, 2, 10, NULL, 0.9, NULL);
SELECT pk, LEAD(pk) OVER (ORDER BY pk) AS l,
LEAD(pk,1) OVER (ORDER BY pk) AS l1,
LEAD(pk,2) OVER (ORDER BY pk) AS l2,
LEAD(pk,0) OVER (ORDER BY pk) AS l0,
LEAD(pk,-1) OVER (ORDER BY pk) AS lm1,
LEAD(pk,-2) OVER (ORDER BY pk) AS lm2
FROM t1;
+----+------+------+------+------+------+------+
| pk | l | l1 | l2 | l0 | lm1 | lm2 |
+----+------+------+------+------+------+------+
| 1 | 2 | 2 | 3 | 1 | NULL | NULL |
| 2 | 3 | 3 | 4 | 2 | 1 | NULL |
| 3 | 4 | 4 | 5 | 3 | 2 | 1 |
| 4 | 5 | 5 | 6 | 4 | 3 | 2 |
| 5 | 6 | 6 | 7 | 5 | 4 | 3 |
| 6 | 7 | 7 | 8 | 6 | 5 | 4 |
| 7 | 8 | 8 | 9 | 7 | 6 | 5 |
| 8 | 9 | 9 | 10 | 8 | 7 | 6 |
| 9 | 10 | 10 | 11 | 9 | 8 | 7 |
| 10 | 11 | 11 | NULL | 10 | 9 | 8 |
| 11 | NULL | NULL | NULL | 11 | 10 | 9 |
+----+------+------+------+------+------+------+
URL: https://mariadb.com/kb/en/lead/https://mariadb.com/kb/en/lead/ � ! * Median Window FunctionThe MEDIAN() window function was first introduced with in
MariaDB 10.3.3.
Syntax
------
MEDIAN(median expression) OVER (
[ PARTITION BY partition_expression ]
)
Description
-----------
MEDIAN() is a window function that returns the median value
of a range of values.
It is a specific case of PERCENTILE_CONT, with an argument
of 0.5 and the ORDER BY column the one in MEDIAN's
argument.
MEDIAN() OVER ( [ PARTITION BY partition_expression] )
Is equivalent to:
PERCENTILE_CONT(0.5) WITHIN
GROUP (ORDER BY ) OVER ( [ PARTITION BY
partition_expression ])
Examples
--------
CREATE TABLE book_rating (name CHAR(30), star_rating
TINYINT);
INSERT INTO book_rating VALUES ('Lord of the Ladybirds',
5);
INSERT INTO book_rating VALUES ('Lord of the Ladybirds',
3);
INSERT INTO book_rating VALUES ('Lady of the Flies', 1);
INSERT INTO book_rating VALUES ('Lady of the Flies', 2);
INSERT INTO book_rating VALUES ('Lady of the Flies', 5);
SELECT name, median(star_rating) OVER (PARTITION BY name)
FROM book_rating;
+-----------------------+----------------------------------------------+
| name | median(star_rating) OVER (PARTITION BY name) |
+-----------------------+----------------------------------------------+
| Lord of the Ladybirds | 4.0000000000 |
| Lord of the Ladybirds | 4.0000000000 |
| Lady of the Flies | 2.0000000000 |
| Lady of the Flies | 2.0000000000 |
| Lady of the Flies | 2.0000000000 |
+-----------------------+----------------------------------------------+
URL: https://mariadb.com/kb/en/median/https://mariadb.com/kb/en/median/ � � * NTILEThe NTILE() function was first introduced with window
functions in MariaDB 10.2.0.
Syntax
------
NTILE (expr) OVER (
[ PARTITION BY partition_expression ]
[ ORDER BY order_list ]
)
Description
-----------
NTILE() is a window function that returns an integer
indicating which group a given row falls into. The number of
groups is specified in the argument (expr), starting at one.
Ordered rows in the partition are divided into the specified
number of groups with as equal a size as possible.
Examples
--------
create table t1 (
pk int primary key,
a int,
b int
);
insert into t1 values
(11 , 0, 10),
(12 , 0, 10),
(13 , 1, 10),
(14 , 1, 10),
(18 , 2, 10),
(15 , 2, 20),
(16 , 2, 20),
(17 , 2, 20),
(19 , 4, 20),
(20 , 4, 20);
select pk, a, b,
ntile(1) over (order by pk)
from t1;
+----+------+------+-----------------------------+
| pk | a | b | ntile(1) over (order by pk) |
+----+------+------+-----------------------------+
| 11 | 0 | 10 | 1 |
| 12 | 0 | 10 | 1 |
| 13 | 1 | 10 | 1 |
| 14 | 1 | 10 | 1 |
| 15 | 2 | 20 | 1 |
| 16 | 2 | 20 | 1 |
| 17 | 2 | 20 | 1 |
| 18 | 2 | 10 | 1 |
| 19 | 4 | 20 | 1 |
| 20 | 4 | 20 | 1 |
+----+------+------+-----------------------------+
select pk, a, b,
ntile(4) over (order by pk)
from t1;
+----+------+------+-----------------------------+
| pk | a | b | ntile(4) over (order by pk) |
+----+------+------+-----------------------------+
| 11 | 0 | 10 | 1 |
| 12 | 0 | 10 | 1 |
| 13 | 1 | 10 | 1 |
| 14 | 1 | 10 | 2 |
| 15 | 2 | 20 | 2 |
| 16 | 2 | 20 | 2 |
| 17 | 2 | 20 | 3 |
| 18 | 2 | 10 | 3 |
| 19 | 4 | 20 | 4 |
| 20 | 4 | 20 | 4 |
+----+------+------+-----------------------------+
URL: https://mariadb.com/kb/en/ntile/https://mariadb.com/kb/en/ntile/ �
�^I R��p� � � \ ' * PERCENT_RANKThe PERCENT_RANK() function was first introduced with window
functions in MariaDB 10.2.0.
Syntax
------
PERCENT_RANK() OVER (
[ PARTITION BY partition_expression ]
[ ORDER BY order_list ]
)
Description
-----------
PERCENT_RANK() is a window function that returns the
relative percent rank of a given row. The following formula
is used to calculate the percent rank:
(rank - 1) / (number of rows in the window or partition - 1)
Examples
--------
create table t1 (
pk int primary key,
a int,
b int
);
insert into t1 values
( 1 , 0, 10),
( 2 , 0, 10),
( 3 , 1, 10),
( 4 , 1, 10),
( 8 , 2, 10),
( 5 , 2, 20),
( 6 , 2, 20),
( 7 , 2, 20),
( 9 , 4, 20),
(10 , 4, 20);
select pk, a, b,
rank() over (order by a) as rank,
percent_rank() over (order by a) as pct_rank,
cume_dist() over (order by a) as cume_dist
from t1;
+----+------+------+------+--------------+--------------+
| pk | a | b | rank | pct_rank | cume_dist |
+----+------+------+------+--------------+--------------+
| 1 | 0 | 10 | 1 | 0.0000000000 | 0.2000000000 |
| 2 | 0 | 10 | 1 | 0.0000000000 | 0.2000000000 |
| 3 | 1 | 10 | 3 | 0.2222222222 | 0.4000000000 |
| 4 | 1 | 10 | 3 | 0.2222222222 | 0.4000000000 |
| 5 | 2 | 20 | 5 | 0.4444444444 | 0.8000000000 |
| 6 | 2 | 20 | 5 | 0.4444444444 | 0.8000000000 |
| 7 | 2 | 20 | 5 | 0.4444444444 | 0.8000000000 |
| 8 | 2 | 10 | 5 | 0.4444444444 | 0.8000000000 |
| 9 | 4 | 20 | 9 | 0.8888888889 | 1.0000000000 |
| 10 | 4 | 20 | 9 | 0.8888888889 | 1.0000000000 |
+----+------+------+------+--------------+--------------+
select pk, a, b,
percent_rank() over (order by pk) as pct_rank,
cume_dist() over (order by pk) as cume_dist
from t1 order by pk;
+----+------+------+--------------+--------------+
| pk | a | b | pct_rank | cume_dist |
+----+------+------+--------------+--------------+
| 1 | 0 | 10 | 0.0000000000 | 0.1000000000 |
| 2 | 0 | 10 | 0.1111111111 | 0.2000000000 |
| 3 | 1 | 10 | 0.2222222222 | 0.3000000000 |
| 4 | 1 | 10 | 0.3333333333 | 0.4000000000 |
| 5 | 2 | 20 | 0.4444444444 | 0.5000000000 |
| 6 | 2 | 20 | 0.5555555556 | 0.6000000000 |
| 7 | 2 | 20 | 0.6666666667 | 0.7000000000 |
| 8 | 2 | 10 | 0.7777777778 | 0.8000000000 |
| 9 | 4 | 20 | 0.8888888889 | 0.9000000000 |
| 10 | 4 | 20 | 1.0000000000 | 1.0000000000 |
+----+------+------+--------------+--------------+
select pk, a, b,
percent_rank() over (partition by a order by a) as
pct_rank,
cume_dist() over (partition by a order by a) as cume_dist
from t1;
+----+------+------+--------------+--------------+
| pk | a | b | pct_rank | cume_dist |
+----+------+------+--------------+--------------+
| 1 | 0 | 10 | 0.0000000000 | 1.0000000000 |
| 2 | 0 | 10 | 0.0000000000 | 1.0000000000 |
| 3 | 1 | 10 | 0.0000000000 | 1.0000000000 |
| 4 | 1 | 10 | 0.0000000000 | 1.0000000000 |
| 5 | 2 | 20 | 0.0000000000 | 1.0000000000 |
| 6 | 2 | 20 | 0.0000000000 | 1.0000000000 |
| 7 | 2 | 20 | 0.0000000000 | 1.0000000000 |
| 8 | 2 | 10 | 0.0000000000 | 1.0000000000 |
| 9 | 4 | 20 | 0.0000000000 | 1.0000000000 |
| 10 | 4 | 20 | 0.0000000000 | 1.0000000000 |
+----+------+------+--------------+--------------+
URL: https://mariadb.com/kb/en/percent_rank/https://mariadb.com/kb/en/percent_rank/ � � * * PERCENTILE_DISCThe PERCENTILE_DISC() window function was first introduced
with in MariaDB 10.3.3.
Syntax
------
Description
-----------
PERCENTILE_DISC() (standing for discrete percentile) is a
window function which returns the first value in the set
whose ordered position is the same or more than the
specified fraction.
Essentially, the following process is followed to find the
value to return:
Get the number of rows in the partition.
Walk through the partition, in order, until finding the the
first row with CUME_DIST() > function_argument.
Examples
--------
CREATE TABLE book_rating (name CHAR(30), star_rating
TINYINT);
INSERT INTO book_rating VALUES ('Lord of the Ladybirds',
5);
INSERT INTO book_rating VALUES ('Lord of the Ladybirds',
3);
INSERT INTO book_rating VALUES ('Lady of the Flies', 1);
INSERT INTO book_rating VALUES ('Lady of the Flies', 2);
INSERT INTO book_rating VALUES ('Lady of the Flies', 5);
SELECT name, PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY
star_rating)
OVER (PARTITION BY name) AS pc FROM book_rating;
+-----------------------+------+
| name | pc |
+-----------------------+------+
| Lord of the Ladybirds | 3 |
| Lord of the Ladybirds | 3 |
| Lady of the Flies | 2 |
| Lady of the Flies | 2 |
| Lady of the Flies | 2 |
+-----------------------+------+
5 rows in set (0.000 sec)
SELECT name, PERCENTILE_DISC(0) WITHIN GROUP (ORDER BY
star_rating)
OVER (PARTITION BY name) AS pc FROM book_rating;
+-----------------------+------+
| name | pc |
+-----------------------+------+
| Lord of the Ladybirds | 3 |
| Lord of the Ladybirds | 3 |
| Lady of the Flies | 1 |
| Lady of the Flies | 1 |
| Lady of the Flies | 1 |
+-----------------------+------+
5 rows in set (0.000 sec)
SELECT name, PERCENTILE_DISC(1) WITHIN GROUP (ORDER BY
star_rating)
OVER (PARTITION BY name) AS pc FROM book_rating;
+-----------------------+------+
| name | pc |
+-----------------------+------+
| Lord of the Ladybirds | 5 |
| Lord of the Ladybirds | 5 |
| Lady of the Flies | 5 |
| Lady of the Flies | 5 |
| Lady of the Flies | 5 |
+-----------------------+------+
5 rows in set (0.000 sec)
SELECT name, PERCENTILE_DISC(0.6) WITHIN GROUP (ORDER BY
star_rating)
OVER (PARTITION BY name) AS pc FROM book_rating;
+-----------------------+------+
| name | pc |
+-----------------------+------+
| Lord of the Ladybirds | 5 |
| Lord of the Ladybirds | 5 |
| Lady of the Flies | 2 |
| Lady of the Flies | 2 |
| Lady of the Flies | 2 |
+-----------------------+------
URL: https://mariadb.com/kb/en/percentile_disc/https://mariadb.com/kb/en/percentile_disc/ � 9
� ��� �G � � * * PERCENTILE_CONTThe PERCENTILE_CONT() window function was first introduced
with in MariaDB 10.3.3.
Syntax
------
Description
-----------
PERCENTILE_CONT() (standing for continuous percentile) is a
window function which returns a value which corresponds to
the given fraction in the sort order. If required, it will
interpolate between adjacent input items.
Essentially, the following process is followed to find the
value to return:
Get the number of rows in the partition, denoted by N
RN = p*(N-1), where p denotes the argument to the
PERCENTILE_CONT function
calculate the FRN(floor row number) and CRN(column row
number for the group( FRN= floor(RN) and CRN = ceil(RN))
look up rows FRN and CRN
If (CRN = FRN = RN) then the result is (value of expression
from row at RN)
Otherwise the result is
(CRN - RN) * (value of expression for row at FRN) +
(RN - FRN) * (value of expression for row at CRN)
The MEDIAN function is a specific case of PERCENTILE_CONT,
equivalent to PERCENTILE_CONT(0.5).
Examples
--------
CREATE TABLE book_rating (name CHAR(30), star_rating
TINYINT);
INSERT INTO book_rating VALUES ('Lord of the Ladybirds',
5);
INSERT INTO book_rating VALUES ('Lord of the Ladybirds',
3);
INSERT INTO book_rating VALUES ('Lady of the Flies', 1);
INSERT INTO book_rating VALUES ('Lady of the Flies', 2);
INSERT INTO book_rating VALUES ('Lady of the Flies', 5);
SELECT name, PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY
star_rating)
OVER (PARTITION BY name) AS pc
FROM book_rating;
+-----------------------+--------------+
| name | pc |
+-----------------------+--------------+
| Lord of the Ladybirds | 4.0000000000 |
| Lord of the Ladybirds | 4.0000000000 |
| Lady of the Flies | 2.0000000000 |
| Lady of the Flies | 2.0000000000 |
| Lady of the Flies | 2.0000000000 |
+-----------------------+--------------+
SELECT name, PERCENTILE_CONT(1) WITHIN GROUP (ORDER BY
star_rating)
OVER (PARTITION BY name) AS pc
FROM book_rating;
+-----------------------+--------------+
| name | pc |
+-----------------------+--------------+
| Lord of the Ladybirds | 5.0000000000 |
| Lord of the Ladybirds | 5.0000000000 |
| Lady of the Flies | 5.0000000000 |
| Lady of the Flies | 5.0000000000 |
| Lady of the Flies | 5.0000000000 |
+-----------------------+--------------+
SELECT name, PERCENTILE_CONT(0) WITHIN GROUP (ORDER BY
star_rating)
OVER (PARTITION BY name) AS pc
FROM book_rating;
+-----------------------+--------------+
| name | pc |
+-----------------------+--------------+
| Lord of the Ladybirds | 3.0000000000 |
| Lord of the Ladybirds | 3.0000000000 |
| Lady of the Flies | 1.0000000000 |
| Lady of the Flies | 1.0000000000 |
| Lady of the Flies | 1.0000000000 |
+-----------------------+--------------+
SELECT name, PERCENTILE_CONT(0.6) WITHIN GROUP (ORDER BY
star_rating)
OVER (PARTITION BY name) AS pc
FROM book_rating;
+-----------------------+--------------+
| name | pc |
+-----------------------+--------------+
| Lord of the Ladybirds | 4.2000000000 |
| Lord of the Ladybirds | 4.2000000000 |
| Lady of the Flies | 2.6000000000 |
| Lady of the Flies | 2.6000000000 |
| Lady of the Flies | 2.6000000000 |
+-----------------------+--------------+
URL: https://mariadb.com/kb/en/percentile_cont/https://mariadb.com/kb/en/percentile_cont/ � * RANKThe RANK() function was first introduced with window
functions in MariaDB 10.2.0.
Syntax
------
RANK() OVER (
[ PARTITION BY partition_expression ]
[ ORDER BY order_list ]
)
Description
-----------
RANK() is a window function that displays the number of a
given row, starting at one and following the ORDER BY
sequence of the window function, with identical values
receiving the same result. It is similar to the ROW_NUMBER()
function except that in that function, identical values will
receive a different row number for each result.
Examples
--------
The distinction between DENSE_RANK(), RANK() and
ROW_NUMBER():
CREATE TABLE student(course VARCHAR(10), mark int, name
varchar(10));
INSERT INTO student VALUES
('Maths', 60, 'Thulile'),
('Maths', 60, 'Pritha'),
('Maths', 70, 'Voitto'),
('Maths', 55, 'Chun'),
('Biology', 60, 'Bilal'),
('Biology', 70, 'Roger');
SELECT
RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS
rank,
DENSE_RANK() OVER (PARTITION BY course ORDER BY mark DESC)
AS dense_rank,
ROW_NUMBER() OVER (PARTITION BY course ORDER BY mark DESC)
AS row_num,
course, mark, name
FROM student ORDER BY course, mark DESC;
+------+------------+---------+---------+------+---------+
| rank | dense_rank | row_num | course | mark | name |
+------+------------+---------+---------+------+---------+
| 1 | 1 | 1 | Biology | 70 | Roger |
| 2 | 2 | 2 | Biology | 60 | Bilal |
| 1 | 1 | 1 | Maths | 70 | Voitto |
| 2 | 2 | 2 | Maths | 60 | Thulile |
| 2 | 2 | 3 | Maths | 60 | Pritha |
| 4 | 3 | 4 | Maths | 55 | Chun |
+------+------------+---------+---------+------+---------+
URL: https://mariadb.com/kb/en/rank/https://mariadb.com/kb/en/rank/ � � � #��� �a �
�% * ROW_NUMBERROW_NUMBER() was first introduced with window functions in
MariaDB 10.2.0.
Syntax
------
ROW_NUMBER() OVER (
[ PARTITION BY partition_expression ]
[ ORDER BY order_list ]
)
Description
-----------
ROW_NUMBER() is a window function that displays the number
of a given row, starting at one and following the ORDER BY
sequence of the window function, with identical values
receiving different row numbers. It is similar to the RANK()
and DENSE_RANK() functions except that in that function,
identical values will receive the same rank for each result.
Examples
--------
The distinction between DENSE_RANK(), RANK() and
ROW_NUMBER():
CREATE TABLE student(course VARCHAR(10), mark int, name
varchar(10));
INSERT INTO student VALUES
('Maths', 60, 'Thulile'),
('Maths', 60, 'Pritha'),
('Maths', 70, 'Voitto'),
('Maths', 55, 'Chun'),
('Biology', 60, 'Bilal'),
('Biology', 70, 'Roger');
SELECT
RANK() OVER (PARTITION BY course ORDER BY mark DESC) AS
rank,
DENSE_RANK() OVER (PARTITION BY course ORDER BY mark DESC)
AS dense_rank,
ROW_NUMBER() OVER (PARTITION BY course ORDER BY mark DESC)
AS row_num,
course, mark, name
FROM student ORDER BY course, mark DESC;
+------+------------+---------+---------+------+---------+
| rank | dense_rank | row_num | course | mark | name |
+------+------------+---------+---------+------+---------+
| 1 | 1 | 1 | Biology | 70 | Roger |
| 2 | 2 | 2 | Biology | 60 | Bilal |
| 1 | 1 | 1 | Maths | 70 | Voitto |
| 2 | 2 | 2 | Maths | 60 | Thulile |
| 2 | 2 | 3 | Maths | 60 | Pritha |
| 4 | 3 | 4 | Maths | 55 | Chun |
+------+------------+---------+---------+------+---------+
URL: https://mariadb.com/kb/en/row_number/https://mariadb.com/kb/en/row_number/ � �/ + SPIDER_BG_DIRECT_SQLSyntax
------
SPIDER_BG_DIRECT_SQL('sql', 'tmp_table_list',
'parameters')
Description
-----------
Executes the given SQL statement in the background on the
remote server, as defined in the parameters listing. If the
query returns a result-set, it sttores the results in the
given temporary table. When the given SQL statement executes
successfully, this function returns the number of called
UDF's. It returns 0 when the given SQL statement fails.
This function is a UDF installed with the Spider storage
engine.
Examples
--------
SELECT SPIDER_BG_DIRECT_SQL('SELECT * FROM example_table',
'',
'srv "node1", port "8607"') AS "Direct Query";
+--------------+
| Direct Query |
+--------------+
| 1 |
+--------------+
Parameters
error_rw_mode
Description: Returns empty results on network error.
0 : Return error on getting network error.
1: Return 0 records on getting network error.
Default Table Value: 0
DSN Parameter Name: erwm
URL: https://mariadb.com/kb/en/spider_bg_direct_sql/https://mariadb.com/kb/en/spider_bg_direct_sql/ � *- + SPIDER_COPY_TABLESSyntax
------
SPIDER_COPY_TABLES(spider_table_name,
source_link_id, destination_link_id_list [,parameters])
Description
-----------
A UDF installed with the Spider Storage Engine, this
function copies table data from source_link_id to
destination_link_id_list. The service does not need to be
stopped in order to copy.
If the Spider table is partitioned, the name must be of the
format table_name#P#partition_name. The partition name can
be viewed in the mysql.spider_tables table, for example:
SELECT table_name FROM mysql.spider_tables;
+-------------+
| table_name |
+-------------+
| spt_a#P#pt1 |
| spt_a#P#pt2 |
| spt_a#P#pt3 |
+-------------+
Returns 1 if the data was copied successfully, or 0 if
copying the data failed.
URL: https://mariadb.com/kb/en/spider_copy_tables/https://mariadb.com/kb/en/spider_copy_tables/ � L, + SPIDER_DIRECT_SQLSyntax
------
SPIDER_DIRECT_SQL('sql', 'tmp_table_list',
'parameters')
Description
-----------
A UDF installed with the Spider Storage Engine, this
function is used to execute the SQL string sql on the remote
server, as defined in parameters. If any resultsets are
returned, they are stored in the tmp_table_list.
The function returns 1 if the SQL executes successfully, or
0 if it fails.
Examples
--------
SELECT SPIDER_DIRECT_SQL('SELECT * FROM s', '', 'srv
"node1", port "8607"');
+----------------------------------------------------------------------+
| SPIDER_DIRECT_SQL('SELECT * FROM s', '', 'srv
"node1", port "8607"') |
+----------------------------------------------------------------------+
| 1 |
+----------------------------------------------------------------------+
URL: https://mariadb.com/kb/en/spider_direct_sql/https://mariadb.com/kb/en/spider_direct_sql/ �
!% , COLUMN_ADDThe Dynamic columns feature was introduced in MariaDB 5.3.
Syntax
------
COLUMN_ADD(dyncol_blob, column_nr, value [as type],
[column_nr, value [as type]]...);
COLUMN_ADD(dyncol_blob, column_name, value [as type],
[column_name, value [as type]]...);
Description
-----------
Adds or updates dynamic columns.
dyncol_blob must be either a valid dynamic columns blob (for
example, COLUMN_CREATE returns such blob), or an empty
string.
column_name specifies the name of the column to be added. If
dyncol_blob already has a column with this name, it will be
overwritten.
value specifies the new value for the column. Passing a NULL
value will cause the column to be deleted.
as type is optional. See #datatypes section for a discussion
about types.
The return value is a dynamic column blob after the
modifications.
Examples
--------
-- MariaDB 5.3+:
UPDATE tbl SET dyncol_blob=COLUMN_ADD(dyncol_blob, 1
/*column id*/, "value") WHERE id=1;
-- MariaDB 10.0.1+:
UPDATE t1 SET dyncol_blob=COLUMN_ADD(dyncol_blob,
"column_name", "value") WHERE id=1;
Note: COLUMN_ADD() is a regular function (just like
CONCAT()), hence, in order to update the value in the table
you have to use the UPDATE ... SET
dynamic_col=COLUMN_ADD(dynamic_col,
....) pattern.
URL: https://mariadb.com/kb/en/column_add/https://mariadb.com/kb/en/column_add/ )^�� w�? ��O�3 �a �
w( , COLUMN_CREATEThe Dynamic columns feature was introduced in MariaDB 5.3.
Syntax
------
COLUMN_CREATE(column_nr, value [as type], [column_nr, value
[as type]]...);
COLUMN_CREATE(column_name, value [as type], [column_name,
value [as type]]...);
Description
-----------
Returns a dynamic columns blob that stores the specified
columns with values.
The return value is suitable for
storing in a table
further modification with other dynamic columns functions
The as type part allows one to specify the value type. In
most cases,
this is redundant because MariaDB will be able to deduce the
type of the
value. Explicit type specification may be needed when the
type of the value is
not apparent. For example, a literal '2012-12-01' has a
CHAR type by
default, one will need to specify '2012-12-01' AS DATE to
have it stored as
a date. See Dynamic Columns:Datatypes for further details.
Examples
--------
-- MariaDB 5.3+:
INSERT INTO tbl SET dyncol_blob=COLUMN_CREATE(1 /*column
id*/, "value");
-- MariaDB 10.0.1+:
INSERT INTO tbl SET
dyncol_blob=COLUMN_CREATE("column_name", "value");
URL: https://mariadb.com/kb/en/column_create/https://mariadb.com/kb/en/column_create/ �
�% , COLUMN_GETThe Dynamic columns feature was introduced in MariaDB 5.3.
Syntax
------
COLUMN_GET(dyncol_blob, column_nr as type);
COLUMN_GET(dyncol_blob, column_name as type);
Description
-----------
Gets the value of a dynamic column by its name. If no column
with the given name exists, NULL will be returned.
column_name as type requires that one specify the datatype
of the dynamic column they are reading.
This may seem counter-intuitive: why would one need to
specify which datatype they're retrieving? Can't the
dynamic columns system figure the datatype from the data
being stored?
The answer is: SQL is a statically-typed language. The SQL
interpreter needs to know the datatypes of all expressions
before the query is run (for example, when one is using
prepared statements and runs "select COLUMN_GET(...)", the
prepared statement API requires the server to inform the
client about the datatype of the column being read before
the query is executed and the server can see what datatype
the column actually has).
A note about lengths
If you're running queries like:
SELECT COLUMN_GET(blob, 'colname' as CHAR) ...
without specifying a maximum length (i.e. using #as CHAR#,
not as CHAR(n)), MariaDB will report the maximum length of
the resultset column to be 53,6870,911 for MariaDB
5.3-10.0.0 and 16,777,216 for MariaDB 10.0.1+. This may
cause excessive memory usage in some client libraries,
because they try to pre-allocate a buffer of maximum
resultset width. To avoid this problem, use CHAR(n) whenever
you're using COLUMN_GET in the select list.
See Dynamic Columns:Datatypes for more information about
datatypes.
URL: https://mariadb.com/kb/en/column_get/https://mariadb.com/kb/en/column_get/ � �& , COLUMN_JSONCOLUMN_JSON was introduced in MariaDB 10.0.1
Syntax
------
COLUMN_JSON(dyncol_blob)
Description
-----------
Returns a JSON representation of data in dyncol_blob. Can
also be used to display nested columns. See dynamic columns
for more information.
Example
select item_name, COLUMN_JSON(dynamic_cols) from assets;
+-----------------+----------------------------------------+
| item_name | COLUMN_JSON(dynamic_cols) |
+-----------------+----------------------------------------+
| MariaDB T-shirt | {"size":"XL","color":"blue"} |
| Thinkpad Laptop | {"color":"black","warranty":"3
years"} |
+-----------------+----------------------------------------+
Limitation: COLUMN_JSON will decode nested dynamic columns
at a nesting level of not more than 10 levels deep. Dynamic
columns that are nested deeper than 10 levels will be shown
as BINARY string, without encoding.
URL: https://mariadb.com/kb/en/column_json/https://mariadb.com/kb/en/column_json/ � ��� �L[�@ �� � �8 . Instant ADD COLUMN for InnoDBInstant ALTER TABLE ... ADD COLUMN for InnoDB was introduced
in MariaDB 10.3.2. The INSTANT option for the ALGORITHM
clause was introduced in MariaDB 10.3.7.
Normally, adding a column to a table requires the full table
to be rebuilt. The complexity of the operation is
proportional to the size of the table, or O(n·m) where n is
the number of rows in the table and m is the number of
indexes.
In MariaDB 10.0 and later, the ALTER TABLE statement
supports online DDL for storage engines that have
implemented the relevant online DDL algorithms and locking
strategies.
The InnoDB storage engine has implemented online DDL for
many operations. These online DDL optimizations allow
concurrent DML to the table in many cases, even if the table
needs to be rebuilt.
See InnoDB Online DDL Overview for more information about
online DDL with InnoDB.
Allowing concurrent DML during the operation does not solve
all problems. When a column was added to a table with the
older in-place optimization, the resulting table rebuild
could still significantly increase the I/O and memory
consumption and cause replication lag.
In contrast, with the new instant ALTER TABLE ... ADD
COLUMN, all that is needed is an O(log n) operation to
insert a special hidden record into the table, and an update
of the data dictionary. For a large table, instead of taking
several hours, the operation would be completed in the blink
of an eye. The ALTER TABLE ... ADD COLUMN operation is only
slightly more expensive than a regular INSERT, due to
locking constraints.
In the past, some developers may have implemented a kind of
"instant add column" in the application by encoding
multiple columns in a single TEXT or BLOB column. MariaDB
Dynamic Columns was an early example of that. A more recent
example is JSON and related string manipulation functions.
Adding real columns has the following advantages over
encoding columns into a single "expandable" column:
Efficient storage in a native binary format
Data type safety
Indexes can be built natively
Constraints are available: UNIQUE, CHECK, FOREIGN KEY
DEFAULT values can be specified
Triggers can be written more easily
With instant ALTER TABLE ... ADD COLUMN, you can enjoy all
the benefits of structured storage without the drawback of
having to rebuild the table.
Instant ALTER TABLE ... ADD COLUMN is available for both old
and new InnoDB tables. Basically you can just upgrade from
MySQL 5.x or MariaDB and start adding columns instantly.
Columns instantly added to a table exist in a separate data
structure from the main table definition, similar to how
InnoDB separates BLOB columns. If the table ever becomes
empty, (such as from TRUNCATE or DELETE statements), InnoDB
incorporates the instantly added columns into the main table
definition. See InnoDB Online DDL Operations with
ALGORITHM=INSTANT: Non-canonical Storage Format Caused by
Some Operations for more information.
The operation is also crash safe. If the server is killed
while executing an instant ALTER TABLE ... ADD COLUMN, when
the table is restored InnoDB integrates the new column,
flattening the table definition.
Limitations
In MariaDB 10.3, instant ALTER TABLE ... ADD COLUMN only
applies when the added columns appear last in the table. The
place specifier LAST is the default. If AFTER col is
specified, then col must be the last column, or the
operation will require the table to be rebuilt. In MariaDB
10.4, this restriction has been lifted.
If the table contains a hidden FTS_DOC_ID column due to a
FULLTEXT INDEX, then instant ALTER TABLE ... ADD COLUMN will
not be possible.
InnoDB data files after instant ALTER TABLE ... ADD COLUMN
cannot be imported to older versions of MariaDB or MySQL
without first being rebuilt.
After using Instant ALTER TABLE ... ADD COLUMN, any
table-rebuilding operation such as ALTER TABLE … FORCE
will incorporate instantaneously added columns into the main
table body.
Instant ALTER TABLE ... ADD COLUMN is not available for
ROW_FORMAT=COMPRESSED.
In MariaDB 10.3, ALTER TABLE … DROP COLUMN requires the
table to be rebuilt. In MariaDB 10.4, this restriction has
been lifted.
Example
CREATE TABLE t(id INT PRIMARY KEY, u INT UNSIGNED NOT NULL
UNIQUE)
ENGINE=InnoDB;
INSERT INTO t(id,u) VALUES(1,1),(2,2),(3,3);
ALTER TABLE t ADD COLUMN
(d DATETIME DEFAULT current_timestamp(),
p POINT NOT NULL DEFAULT ST_GeomFromText('POINT(0 0)'),
t TEXT CHARSET utf8 DEFAULT 'The quick brown fox jumps
over the lazy dog');
UPDATE t SET t=NULL WHERE id=3;
SELECT id,u,d,ST_AsText(p),t FROM t;
SELECT variable_value FROM information_schema.global_status
WHERE variable_name = 'innodb_instant_alter_column';
The above example illustrates that when the added columns
are declared NOT NULL, a DEFAULT value must be available,
either implied by the data type or set explicitly by the
user. The expression need not be constant, but it must not
refer to the columns of the table, such as DEFAULT u+1 (a
MariaDB extension). The DEFAULT current_timestamp() would be
evaluated at the time of the ALTER TABLE and apply to each
row, like it does for non-instant ALTER TABLE. If a
subsequent ALTER TABLE changes the DEFAULT value for
subsequent INSERT, the values of the columns in existing
records will naturally be unaffected.
The design was brainstormed in April by engineers from
MariaDB Corporation, Alibaba and Tencent. A prototype was
developed by Vin Chen (陈福荣) from the Tencent Game DBA
Team.
URL:
https://mariadb.com/kb/en/instant-add-column-for-innodb/https://mariadb.com/kb/en/instant-add-column-for-innodb/ !ʣ
� � � s3 0 Full-Text Index OverviewMariaDB has support for full-text indexing and searching:
A full-text index in MariaDB is an index of type FULLTEXT,
and it allows more options when searching for portions of
text from a field.
Full-text indexes can be used only with MyISAM and Aria
tables, from MariaDB 10.0.5 with InnoDB tables and from
MariaDB 10.0.15 with Mroonga tables, and can be created only
for CHAR, VARCHAR, or TEXT columns.
Partitioned tables cannot contain fulltext indexes, even if
the storage engine supports them.
A FULLTEXT index definition can be given in the CREATE TABLE
statement when a
table is created, or added later using ALTER TABLE or
CREATE INDEX.
For large data sets, it is much faster to load your data
into a table that
has no FULLTEXT index and then create the index after that,
than to load data
into a table that has an existing FULLTEXT index.
Full-text searching is performed using MATCH() ... AGAINST
syntax.
MATCH() takes a comma-separated list that names the columns
to be
searched. AGAINST takes a string to search for, and an
optional
modifier that indicates what type of search to perform. The
search
string must be a literal string, not a variable or a column
name.
MATCH (col1,col2,...) AGAINST (expr [search_modifier])
Excluded Results
Partial words are excluded.
Words less than 4 characters in length (3 or less) will not
be stored in the fulltext index. This value can be adjusted
by changing the ft_min_word_length system variable (or, for
InnoDB, innodb_ft_min_token_size).
Words longer than 84 characters in length will also not be
stored in the fulltext index. This values can be adjusted by
changing the ft_max_word_length system variable (or, for
InnoDB, innodb_ft_max_token_size).
Stopwords are a list of common words such as "once" or
"then" that do not reflect in the search results unless IN
BOOLEAN MODE is used. The stopword list for MyISAM/Aria
tables and InnoDB tables can differ. See stopwords for
details and a full list, as well as for details on how to
change the default list.
For MyISAM/Aria fulltext indexes only, if a word appears in
more than half the rows, it is also excluded from the
results of a fulltext search.
For InnoDB indexes, only committed rows appear -
modifications from the current transaction do not apply.
Relevance
MariaDB calculates a relevance for each result, based on a
number of factors, including the number of words in the
index, the number of unique words in a row, the total number
of words in both the index and the result, and the weight of
the word. In English, 'cool' will be weighted less than
'dandy', at least at present! The relevance can be
returned as part of a query simply by using the MATCH
function in the field list.
Types of Full-Text search
IN NATURAL LANGUAGE MODE
IN NATURAL LANGUAGE MODE is the default type of full-text
search, and the keywords can be omitted. There are no
special operators, and searches consist of one or more
comma-separated keywords.
Searches are returned in descending order of relevance.
IN BOOLEAN MODE
Boolean search permits the use of a number of special
operators:
Operator | Description |
+ | The word is mandatory in all rows returned. |
- | The word cannot appear in any row returned. |
< | The word that follows has a lower relevance than other
words, although rows containing it will still match |
> | The word that follows has a higher relevance than other
words. |
() | Used to group words into subexpressions. |
~ | The word following contributes negatively to the
relevance of the row (which is different to the '-'
operator, which specifically excludes the word, or the '
URL: https://mariadb.com/kb/en/full-text-index-overview/https://mariadb.com/kb/en/full-text-index-overview/ �� [�