sql-statement-set-variable.md

title	summary	category	aliases
SET [GLOBAL|SESSION] <variable>	TiDB 数据库中 SET [GLOBAL|SESSION] <variable> 的使用概况。	reference	/docs-cn/dev/reference/sql/statements/set-variable/

SET [GLOBAL|SESSION] <variable>

SET [GLOBAL|SESSION] 语句用于在 SESSION 或 GLOBAL 的范围内，对某个 TiDB 的内置变量进行更改。

注意：

与 MySQL 类似，对 GLOBAL 变量的更改不适用于已有连接或本地连接，只有新会话才会反映值的变化。

语法图

SetStmt:

VariableAssignment:

示例

获取 sql_mode 的值：

{{< copyable "sql" >}}

SHOW GLOBAL VARIABLES LIKE 'sql_mode';

+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
| Variable_name | Value                                                                                                                                     |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
| 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 |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

{{< copyable "sql" >}}

SHOW SESSION VARIABLES LIKE 'sql_mode';

+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
| Variable_name | Value                                                                                                                                     |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
| 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 |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

更新全局的 sql_mode：

{{< copyable "sql" >}}

SET GLOBAL sql_mode = 'STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER';

Query OK, 0 rows affected (0.03 sec)

检查更新之后的 sql_mode 的取值，可以看到 SESSION 级别的值没有更新：

{{< copyable "sql" >}}

SHOW GLOBAL VARIABLES LIKE 'sql_mode';

+---------------+-----------------------------------------+
| Variable_name | Value                                   |
+---------------+-----------------------------------------+
| sql_mode      | STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER |
+---------------+-----------------------------------------+
1 row in set (0.00 sec)

{{< copyable "sql" >}}

SHOW SESSION VARIABLES LIKE 'sql_mode';

+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
| Variable_name | Value                                                                                                                                     |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
| 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 |
+---------------+-------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

SET SESSION 则可以立即生效：

{{< copyable "sql" >}}

SET SESSION sql_mode = 'STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER';

Query OK, 0 rows affected (0.01 sec)

{{< copyable "sql" >}}

SHOW SESSION VARIABLES LIKE 'sql_mode';

+---------------+-----------------------------------------+
| Variable_name | Value                                   |
+---------------+-----------------------------------------+
| sql_mode      | STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER |
+---------------+-----------------------------------------+
1 row in set (0.00 sec)

MySQL 兼容性

SET [GLOBAL|SESSION] 语句与 MySQL 完全兼容。如有任何兼容性差异，请在 GitHub 上提交 issue。

另请参阅

• SHOW [GLOBAL|SESSION] VARIABLES