SQL Mode
TiDB servers operate in different SQL modes and apply these modes differently for different clients. SQL mode defines the SQL syntaxes that TiDB supports and the type of data validation check to perform, as described below:
After TiDB is started, modify SET [ SESSION | GLOBAL ] sql_mode='modes' to set SQL mode.
Ensure that you have SUPER privilege when setting SQL mode at GLOBAL level, and your setting at this level only affects the connections established afterwards. Changes to SQL mode at SESSION level only affect the current client.
Modes are a series of different modes separated by commas (','). You can use the SELECT @@sql_mode statement to check the current SQL mode. The default value of SQL mode: ONLY_FULL_GROUP_BY, STRICT_TRANS_TABLES, NO_ZERO_IN_DATE, NO_ZERO_DATE, ERROR_FOR_DIVISION_BY_ZERO, NO_AUTO_CREATE_USER, NO_ENGINE_SUBSTITUTION.
Important sql_mode values
ANSI: This mode complies with standard SQL. In this mode, data is checked. If data does not comply with the defined type or length, the data type is adjusted or trimmed and awarningis returned.STRICT_TRANS_TABLES: Strict mode, where data is strictly checked. If any data is incorrect, it cannot be inserted into a table and an error is returned.TRADITIONAL: In this mode, TiDB behaves like a "traditional" SQL database system. An error instead of a warning is returned when any incorrect value is inserted into a column. Then, theINSERTorUPDATEstatement is immediately stopped.
SQL mode table
| Name | Description |
|---|---|
PIPES_AS_CONCAT | Treats "||" as a string concatenation operator (+) (the same as CONCAT()), not as an OR (full support) |
ANSI_QUOTES | Treats " as an identifier. If ANSI_QUOTES is enabled, only single quotes are treated as string literals, and double quotes are treated as identifiers. Therefore, double quotes cannot be used to quote strings. (full support) |
IGNORE_SPACE | If this mode is enabled, the system ignores space. For example: "user" and "user " are the same. (full support) |
ONLY_FULL_GROUP_BY | If a non-aggregated column that is referred to in SELECT, HAVING, or ORDER BY is absent in GROUP BY, this SQL statement is invalid, because it is abnormal for a column to be absent in GROUP BY but displayed by query. (full support) |
NO_UNSIGNED_SUBTRACTION | Does not mark the result as UNSIGNED if an operand has no symbol in subtraction. (full support) |
NO_DIR_IN_CREATE | Ignores all INDEX DIRECTORY and DATA DIRECTORY directives when a table is created. This option is only useful for secondary replication servers (syntax support only) |
NO_KEY_OPTIONS | When you use the SHOW CREATE TABLE statement, MySQL-specific syntaxes such as ENGINE are not exported. Consider this option when migrating across DB types using mysqldump. (syntax support only) |
NO_FIELD_OPTIONS | When you use the SHOW CREATE TABLE statement, MySQL-specific syntaxes such as ENGINE are not exported. Consider this option when migrating across DB types using mysqldump. (syntax support only) |
NO_TABLE_OPTIONS | When you use the SHOW CREATE TABLE statement, MySQL-specific syntaxes such as ENGINE are not exported. Consider this option when migrating across DB types using mysqldump. (syntax support only) |
NO_AUTO_VALUE_ON_ZERO | If this mode is enabled, when the value passed in the AUTO_INCREMENT column is 0 or a specific value, the system directly writes this value to this column. When NULL is passed, the system automatically generates the next serial number. (full support) |
NO_BACKSLASH_ESCAPES | If this mode is enabled, the \ backslash symbol only stands for itself. (full support) |
STRICT_TRANS_TABLES | Enables the strict mode for the transaction storage engine and rolls back the entire statement after an illegal value is inserted. (full support) |
STRICT_ALL_TABLES | For transactional tables, rolls back the entire transaction statement after an illegal value is inserted. (full support) |
NO_ZERO_IN_DATE | Strict mode, where dates with a month or day part of 0 are not accepted. If you use the IGNORE option, TiDB inserts '0000-00-00' for a similar date. In non-strict mode, this date is accepted but a warning is returned. (full support) |
NO_ZERO_DATE | Does not use '0000-00-00' as a legal date in strict mode. You can still insert a zero date with the IGNORE option. In non-strict mode, this date is accepted but a warning is returned. (full support) |
ALLOW_INVALID_DATES | In this mode, the system does not check the validity of all dates. It only checks the month value ranging from 1 to 12 and the date value ranging from 1 to 31. The mode only applies to DATE and DATATIME columns. All TIMESTAMP columns need a full validity check. (full support) |
ERROR_FOR_DIVISION_BY_ZERO | If this mode is enabled, the system returns an error when handling division by 0 in data-change operations (INSERT or UPDATE). If this mode is not enabled, the system returns a warning and NULL is used instead. (full support) |
NO_AUTO_CREATE_USER | Prevents GRANT from automatically creating new users, except for the specified password (full support) |
HIGH_NOT_PRECEDENCE | The precedence of the NOT operator is such that expressions such as NOT a BETWEEN b AND c are parsed as NOT (a BETWEEN b AND c). In some older versions of MySQL, this expression is parsed as (NOT a) BETWEEN b AND c. (full support) |
NO_ENGINE_SUBSTITUTION | Prevents the automatic replacement of storage engines if the required storage engine is disabled or not compiled. (syntax support only) |
PAD_CHAR_TO_FULL_LENGTH | If this mode is enabled, the system does not trim the trailing spaces for CHAR types. (syntax support only. This mode has been deprecated in MySQL 8.0.) |
REAL_AS_FLOAT | Treats REAL as the synonym of FLOAT, not the synonym of DOUBLE (full support) |
POSTGRESQL | Equivalent to PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE, NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_FIELD_OPTIONS (syntax support only) |
MSSQL | Equivalent to PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE, NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_FIELD_OPTIONS (syntax support only) |
DB2 | Equivalent to PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE, NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_FIELD_OPTIONS (syntax support only) |
MAXDB | Equivalent to PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE, NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_FIELD_OPTIONS, NO_AUTO_CREATE_USER (full support) |
MySQL323 | Equivalent to NO_FIELD_OPTIONS, HIGH_NOT_PRECEDENCE (syntax support only) |
MYSQL40 | Equivalent to NO_FIELD_OPTIONS, HIGH_NOT_PRECEDENCE (syntax support only) |
ANSI | Equivalent to REAL_AS_FLOAT, PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE (syntax support only) |
TRADITIONAL | Equivalent to STRICT_TRANS_TABLES, STRICT_ALL_TABLES, NO_ZERO_IN_DATE, NO_ZERO_DATE, ERROR_FOR_DIVISION_BY_ZERO, NO_AUTO_CREATE_USER (syntax support only) |
ORACLE | Equivalent to PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE, NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_FIELD_OPTIONS, NO_AUTO_CREATE_USER (syntax support only) |