The MySQL server can operate in different SQL modes, and can apply
these modes differently for different clients, depending on the
value of the sql_mode
system
variable. DBAs can set the global SQL mode to match site server
operating requirements, and each application can set its session
SQL mode to its own requirements.
Modes affect the SQL syntax MySQL supports and the data validation checks it performs. This makes it easier to use MySQL in different environments and to use MySQL together with other database servers.
For answers to questions often asked about server SQL modes in MySQL, see Section A.3, “MySQL 5.6 FAQ: Server SQL Mode”.
When working with InnoDB
tables, consider also
the innodb_strict_mode
system
variable. It enables additional error checks for
InnoDB
tables.
The default SQL mode is
NO_ENGINE_SUBSTITUTION
.
To set the SQL mode at server startup, use the
--sql-mode="
option on the command line, or
modes
"sql-mode="
in an option file such as modes
"my.cnf
(Unix
operating systems) or my.ini
(Windows).
modes
is a list of different modes
separated by commas. To clear the SQL mode explicitly, set it to
an empty string using
--sql-mode=""
on the command
line, or sql-mode=""
in an option
file.
MySQL installation programs may configure the SQL mode during
the installation process. For example,
mysql_install_db creates a default option
file named my.cnf
in the base
installation directory. This file contains a line that sets
the SQL mode; see Section 4.4.3, “mysql_install_db — Initialize MySQL Data Directory”.
If the SQL mode differs from the default or from what you expect, check for a setting in an option file that the server reads at startup.
To change the SQL mode at runtime, set the global or session
sql_mode
system variable using
a SET
statement:
SET GLOBAL sql_mode = 'modes';
SET SESSION sql_mode = 'modes';
Setting the GLOBAL
variable requires the
SUPER
privilege and affects the
operation of all clients that connect from that time on. Setting
the SESSION
variable affects only the current
client. Each client can change its session
sql_mode
value at any time.
To determine the current global or session
sql_mode
setting, select its
value:
SELECT @@GLOBAL.sql_mode;
SELECT @@SESSION.sql_mode;
SQL mode and user-defined partitioning. Changing the server SQL mode after creating and inserting data into partitioned tables can cause major changes in the behavior of such tables, and could lead to loss or corruption of data. It is strongly recommended that you never change the SQL mode once you have created tables employing user-defined partitioning.
When replicating partitioned tables, differing SQL modes on the source and replica can also lead to problems. For best results, you should always use the same server SQL mode on the source and replica.
For more information, see Section 19.6, “Restrictions and Limitations on Partitioning”.
The most important sql_mode
values are probably these:
This mode changes syntax and behavior to conform more closely to standard SQL. It is one of the special combination modes listed at the end of this section.
If a value could not be inserted as given into a transactional table, abort the statement. For a nontransactional table, abort the statement if the value occurs in a single-row statement or the first row of a multiple-row statement. More details are given later in this section.
Make MySQL behave like a “traditional” SQL database system. A simple description of this mode is “give an error instead of a warning” when inserting an incorrect value into a column. It is one of the special combination modes listed at the end of this section.
NoteWith
TRADITIONAL
mode enabled, anINSERT
orUPDATE
aborts as soon as an error occurs. If you are using a nontransactional storage engine, this may not be what you want because data changes made prior to the error may not be rolled back, resulting in a “partially done” update.
When this manual refers to “strict mode,” it means
a mode with either or both
STRICT_TRANS_TABLES
or
STRICT_ALL_TABLES
enabled.
The following list describes all supported SQL modes:
Do not perform full checking of dates. Check only that the month is in the range from 1 to 12 and the day is in the range from 1 to 31. This may be useful for Web applications that obtain year, month, and day in three different fields and store exactly what the user inserted, without date validation. This mode applies to
DATE
andDATETIME
columns. It does not apply toTIMESTAMP
columns, which always require a valid date.With
ALLOW_INVALID_DATES
disabled, the server requires that month and day values be legal, and not merely in the range 1 to 12 and 1 to 31, respectively. With strict mode disabled, invalid dates such as'2004-04-31'
are converted to'0000-00-00'
and a warning is generated. With strict mode enabled, invalid dates generate an error. To permit such dates, enableALLOW_INVALID_DATES
.Treat
"
as an identifier quote character (like the`
quote character) and not as a string quote character. You can still use`
to quote identifiers with this mode enabled. WithANSI_QUOTES
enabled, you cannot use double quotation marks to quote literal strings because they are interpreted as identifiers.The
ERROR_FOR_DIVISION_BY_ZERO
mode affects handling of division by zero, which includesMOD(
. For data-change operations (N
,0)INSERT
,UPDATE
), its effect also depends on whether strict SQL mode is enabled.If this mode is not enabled, division by zero inserts
NULL
and produces no warning.If this mode is enabled, division by zero inserts
NULL
and produces a warning.If this mode and strict mode are enabled, division by zero produces an error, unless
IGNORE
is given as well. ForINSERT IGNORE
andUPDATE IGNORE
, division by zero insertsNULL
and produces a warning.
For
SELECT
, division by zero returnsNULL
. EnablingERROR_FOR_DIVISION_BY_ZERO
causes a warning to be produced as well, regardless of whether strict mode is enabled.As of MySQL 5.6.17,
ERROR_FOR_DIVISION_BY_ZERO
is deprecated and setting thesql_mode
value to include it generates a warning.The precedence of the
NOT
operator is such that expressions such asNOT a BETWEEN b AND c
are parsed asNOT (a BETWEEN b AND c)
. In some older versions of MySQL, the expression was parsed as(NOT a) BETWEEN b AND c
. The old higher-precedence behavior can be obtained by enabling theHIGH_NOT_PRECEDENCE
SQL mode.mysql> SET sql_mode = ''; mysql> SELECT NOT 1 BETWEEN -5 AND 5; -> 0 mysql> SET sql_mode = 'HIGH_NOT_PRECEDENCE'; mysql> SELECT NOT 1 BETWEEN -5 AND 5; -> 1
Permit spaces between a function name and the
(
character. This causes built-in function names to be treated as reserved words. As a result, identifiers that are the same as function names must be quoted as described in Section 9.2, “Schema Object Names”. For example, because there is aCOUNT()
function, the use ofcount
as a table name in the following statement causes an error:mysql> CREATE TABLE count (i INT); ERROR 1064 (42000): You have an error in your SQL syntax
The table name should be quoted:
mysql> CREATE TABLE `count` (i INT); Query OK, 0 rows affected (0.00 sec)
The
IGNORE_SPACE
SQL mode applies to built-in functions, not to loadable functions or stored functions. It is always permissible to have spaces after a loadable function or stored function name, regardless of whetherIGNORE_SPACE
is enabled.For further discussion of
IGNORE_SPACE
, see Section 9.2.5, “Function Name Parsing and Resolution”.Prevent the
GRANT
statement from automatically creating new users if it would otherwise do so, unless authentication information is specified. The statement must specify a nonempty password usingIDENTIFIED BY
or an authentication plugin usingIDENTIFIED WITH
.NO_AUTO_VALUE_ON_ZERO
affects handling ofAUTO_INCREMENT
columns. Normally, you generate the next sequence number for the column by inserting eitherNULL
or0
into it.NO_AUTO_VALUE_ON_ZERO
suppresses this behavior for0
so that onlyNULL
generates the next sequence number.This mode can be useful if
0
has been stored in a table'sAUTO_INCREMENT
column. (Storing0
is not a recommended practice, by the way.) For example, if you dump the table with mysqldump and then reload it, MySQL normally generates new sequence numbers when it encounters the0
values, resulting in a table with contents different from the one that was dumped. EnablingNO_AUTO_VALUE_ON_ZERO
before reloading the dump file solves this problem. For this reason, mysqldump automatically includes in its output a statement that enablesNO_AUTO_VALUE_ON_ZERO
.Enabling this mode disables the use of the backslash character (
\
) as an escape character within strings and identifiers. With this mode enabled, backslash becomes an ordinary character like any other, and the default escape sequence forLIKE
expressions is changed so that no escape character is used.When creating a table, ignore all
INDEX DIRECTORY
andDATA DIRECTORY
directives. This option is useful on replica servers.Control automatic substitution of the default storage engine when a statement such as
CREATE TABLE
orALTER TABLE
specifies a storage engine that is disabled or not compiled in.Because storage engines can be pluggable at runtime, unavailable engines are treated the same way:
With
NO_ENGINE_SUBSTITUTION
disabled, forCREATE TABLE
the default engine is used and a warning occurs if the desired engine is unavailable. ForALTER TABLE
, a warning occurs and the table is not altered.With
NO_ENGINE_SUBSTITUTION
enabled, an error occurs and the table is not created or altered if the desired engine is unavailable.Do not print MySQL-specific column options in the output of
SHOW CREATE TABLE
. This mode is used by mysqldump in portability mode.Do not print MySQL-specific index options in the output of
SHOW CREATE TABLE
. This mode is used by mysqldump in portability mode.Do not print MySQL-specific table options (such as
ENGINE
) in the output ofSHOW CREATE TABLE
. This mode is used by mysqldump in portability mode.Subtraction between integer values, where one is of type
UNSIGNED
, produces an unsigned result by default. If the result would otherwise have been negative, an error results:mysql> SET sql_mode = ''; Query OK, 0 rows affected (0.00 sec) mysql> SELECT CAST(0 AS UNSIGNED) - 1; ERROR 1690 (22003): BIGINT UNSIGNED value is out of range in '(cast(0 as unsigned) - 1)'
If the
NO_UNSIGNED_SUBTRACTION
SQL mode is enabled, the result is negative:mysql> SET sql_mode = 'NO_UNSIGNED_SUBTRACTION'; mysql> SELECT CAST(0 AS UNSIGNED) - 1; +-------------------------+ | CAST(0 AS UNSIGNED) - 1 | +-------------------------+ | -1 | +-------------------------+
If the result of such an operation is used to update an
UNSIGNED
integer column, the result is clipped to the maximum value for the column type, or clipped to 0 ifNO_UNSIGNED_SUBTRACTION
is enabled. With strict SQL mode enabled, an error occurs and the column remains unchanged.When
NO_UNSIGNED_SUBTRACTION
is enabled, the subtraction result is signed, even if any operand is unsigned. For example, compare the type of columnc2
in tablet1
with that of columnc2
in tablet2
:mysql> SET sql_mode=''; mysql> CREATE TABLE test (c1 BIGINT UNSIGNED NOT NULL); mysql> CREATE TABLE t1 SELECT c1 - 1 AS c2 FROM test; mysql> DESCRIBE t1; +-------+---------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------------------+------+-----+---------+-------+ | c2 | bigint(21) unsigned | NO | | 0 | | +-------+---------------------+------+-----+---------+-------+ mysql> SET sql_mode='NO_UNSIGNED_SUBTRACTION'; mysql> CREATE TABLE t2 SELECT c1 - 1 AS c2 FROM test; mysql> DESCRIBE t2; +-------+------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+------------+------+-----+---------+-------+ | c2 | bigint(21) | NO | | 0 | | +-------+------------+------+-----+---------+-------+
This means that
BIGINT UNSIGNED
is not 100% usable in all contexts. See Section 12.11, “Cast Functions and Operators”.The
NO_ZERO_DATE
mode affects whether the server permits'0000-00-00'
as a valid date. Its effect also depends on whether strict SQL mode is enabled.If this mode is not enabled,
'0000-00-00'
is permitted and inserts produce no warning.If this mode is enabled,
'0000-00-00'
is permitted and inserts produce a warning.If this mode and strict mode are enabled,
'0000-00-00'
is not permitted and inserts produce an error, unlessIGNORE
is given as well. ForINSERT IGNORE
andUPDATE IGNORE
,'0000-00-00'
is permitted and inserts produce a warning.
As of MySQL 5.6.17,
NO_ZERO_DATE
is deprecated and setting thesql_mode
value to include it generates a warning.The
NO_ZERO_IN_DATE
mode affects whether the server permits dates in which the year part is nonzero but the month or day part is 0. (This mode affects dates such as'2010-00-01'
or'2010-01-00'
, but not'0000-00-00'
. To control whether the server permits'0000-00-00'
, use theNO_ZERO_DATE
mode.) The effect ofNO_ZERO_IN_DATE
also depends on whether strict SQL mode is enabled.If this mode is not enabled, dates with zero parts are permitted and inserts produce no warning.
If this mode is enabled, dates with zero parts are inserted as
'0000-00-00'
and produce a warning.If this mode and strict mode are enabled, dates with zero parts are not permitted and inserts produce an error, unless
IGNORE
is given as well. ForINSERT IGNORE
andUPDATE IGNORE
, dates with zero parts are inserted as'0000-00-00'
and produce a warning.
As of MySQL 5.6.17,
NO_ZERO_IN_DATE
is deprecated and setting thesql_mode
value to include it generates a warning.Reject queries for which the select list,
HAVING
condition, orORDER BY
list refer to nonaggregated columns that are not named in theGROUP BY
clause.A MySQL extension to standard SQL permits references in the
HAVING
clause to aliased expressions in the select list. EnablingONLY_FULL_GROUP_BY
disables this extension, thus requiring theHAVING
clause to be written using unaliased expressions.For additional discussion and examples, see Section 12.19.3, “MySQL Handling of GROUP BY”.
By default, trailing spaces are trimmed from
CHAR
column values on retrieval. IfPAD_CHAR_TO_FULL_LENGTH
is enabled, trimming does not occur and retrievedCHAR
values are padded to their full length. This mode does not apply toVARCHAR
columns, for which trailing spaces are retained on retrieval.mysql> CREATE TABLE t1 (c1 CHAR(10)); Query OK, 0 rows affected (0.37 sec) mysql> INSERT INTO t1 (c1) VALUES('xy'); Query OK, 1 row affected (0.01 sec) mysql> SET sql_mode = ''; Query OK, 0 rows affected (0.00 sec) mysql> SELECT c1, CHAR_LENGTH(c1) FROM t1; +------+-----------------+ | c1 | CHAR_LENGTH(c1) | +------+-----------------+ | xy | 2 | +------+-----------------+ 1 row in set (0.00 sec) mysql> SET sql_mode = 'PAD_CHAR_TO_FULL_LENGTH'; Query OK, 0 rows affected (0.00 sec) mysql> SELECT c1, CHAR_LENGTH(c1) FROM t1; +------------+-----------------+ | c1 | CHAR_LENGTH(c1) | +------------+-----------------+ | xy | 10 | +------------+-----------------+ 1 row in set (0.00 sec)
Treat
||
as a string concatenation operator (same asCONCAT()
) rather than as a synonym forOR
.Treat
REAL
as a synonym forFLOAT
. By default, MySQL treatsREAL
as a synonym forDOUBLE
.Enable strict SQL mode for all storage engines. Invalid data values are rejected. For details, see Strict SQL Mode.
Enable strict SQL mode for transactional storage engines, and when possible for nontransactional storage engines. For details, see Strict SQL Mode.
The following special modes are provided as shorthand for combinations of mode values from the preceding list.
Equivalent to
REAL_AS_FLOAT
,PIPES_AS_CONCAT
,ANSI_QUOTES
,IGNORE_SPACE
.ANSI
mode also causes the server to return an error for queries where a set functionS
with an outer reference
cannot be aggregated in the outer query against which the outer reference has been resolved. This is such a query:S
(outer_ref
)SELECT * FROM t1 WHERE t1.a IN (SELECT MAX(t1.b) FROM t2 WHERE ...);
Here,
MAX(t1.b)
cannot aggregated in the outer query because it appears in theWHERE
clause of that query. Standard SQL requires an error in this situation. IfANSI
mode is not enabled, the server treats
in such queries the same way that it would interpretS
(outer_ref
)
.S
(const
)Equivalent to
PIPES_AS_CONCAT
,ANSI_QUOTES
,IGNORE_SPACE
,NO_KEY_OPTIONS
,NO_TABLE_OPTIONS
,NO_FIELD_OPTIONS
.Equivalent to
PIPES_AS_CONCAT
,ANSI_QUOTES
,IGNORE_SPACE
,NO_KEY_OPTIONS
,NO_TABLE_OPTIONS
,NO_FIELD_OPTIONS
,NO_AUTO_CREATE_USER
.Equivalent to
PIPES_AS_CONCAT
,ANSI_QUOTES
,IGNORE_SPACE
,NO_KEY_OPTIONS
,NO_TABLE_OPTIONS
,NO_FIELD_OPTIONS
.Equivalent to
MYSQL323
,HIGH_NOT_PRECEDENCE
. This meansHIGH_NOT_PRECEDENCE
plus someSHOW CREATE TABLE
behaviors specific toMYSQL323
:TIMESTAMP
column display does not includeDEFAULT
orON UPDATE
attributes.String column display does not include character set and collation attributes. For
CHAR
andVARCHAR
columns, if the collation is binary,BINARY
is appended to the column type.The
ENGINE=
table option displays asengine_name
TYPE=
.engine_name
For
MEMORY
tables, the storage engine is displayed asHEAP
.
Equivalent to
MYSQL40
,HIGH_NOT_PRECEDENCE
. This meansHIGH_NOT_PRECEDENCE
plus some behaviors specific toMYSQL40
. These are the same as forMYSQL323
, except thatSHOW CREATE TABLE
does not displayHEAP
as the storage engine forMEMORY
tables.Equivalent to
PIPES_AS_CONCAT
,ANSI_QUOTES
,IGNORE_SPACE
,NO_KEY_OPTIONS
,NO_TABLE_OPTIONS
,NO_FIELD_OPTIONS
,NO_AUTO_CREATE_USER
.Equivalent to
PIPES_AS_CONCAT
,ANSI_QUOTES
,IGNORE_SPACE
,NO_KEY_OPTIONS
,NO_TABLE_OPTIONS
,NO_FIELD_OPTIONS
.Equivalent to
STRICT_TRANS_TABLES
,STRICT_ALL_TABLES
,NO_ZERO_IN_DATE
,NO_ZERO_DATE
,ERROR_FOR_DIVISION_BY_ZERO
,NO_AUTO_CREATE_USER
, andNO_ENGINE_SUBSTITUTION
.
Strict mode controls how MySQL handles invalid or missing values
in data-change statements such as
INSERT
or
UPDATE
. A value can be invalid
for several reasons. For example, it might have the wrong data
type for the column, or it might be out of range. A value is
missing when a new row to be inserted does not contain a value
for a non-NULL
column that has no explicit
DEFAULT
clause in its definition. (For a
NULL
column, NULL
is
inserted if the value is missing.) Strict mode also affects DDL
statements such as CREATE TABLE
.
If strict mode is not in effect, MySQL inserts adjusted values
for invalid or missing values and produces warnings (see
Section 13.7.5.41, “SHOW WARNINGS Statement”). In strict mode, you can
produce this behavior by using
INSERT IGNORE
or UPDATE
IGNORE
.
For statements such as SELECT
that do not change data, invalid values generate a warning in
strict mode, not an error.
As of MySQL 5.6.11, strict mode produces an error for attempts to create a key that exceeds the maximum key length. Previously, this resulted in a warning and truncation of the key to the maximum key length (the same as when strict mode is not enabled).
Strict mode does not affect whether foreign key constraints are
checked. foreign_key_checks
can
be used for that. (See
Section 5.1.7, “Server System Variables”.)
Strict SQL mode is in effect if either
STRICT_ALL_TABLES
or
STRICT_TRANS_TABLES
is
enabled, although the effects of these modes differ somewhat:
For transactional tables, an error occurs for invalid or missing values in a data-change statement when either
STRICT_ALL_TABLES
orSTRICT_TRANS_TABLES
is enabled. The statement is aborted and rolled back.For nontransactional tables, the behavior is the same for either mode if the bad value occurs in the first row to be inserted or updated: The statement is aborted and the table remains unchanged. If the statement inserts or modifies multiple rows and the bad value occurs in the second or later row, the result depends on which strict mode is enabled:
For
STRICT_ALL_TABLES
, MySQL returns an error and ignores the rest of the rows. However, because the earlier rows have been inserted or updated, the result is a partial update. To avoid this, use single-row statements, which can be aborted without changing the table.For
STRICT_TRANS_TABLES
, MySQL converts an invalid value to the closest valid value for the column and inserts the adjusted value. If a value is missing, MySQL inserts the implicit default value for the column data type. In either case, MySQL generates a warning rather than an error and continues processing the statement. Implicit defaults are described in Section 11.5, “Data Type Default Values”.
Strict mode also affects handling of division by zero, zero
dates, and zeros in dates, in conjunction with the
ERROR_FOR_DIVISION_BY_ZERO
,
NO_ZERO_DATE
, and
NO_ZERO_IN_DATE
modes. For
details, see the descriptions of those modes.