sql-statement-show-variables.md

title	SHOW [GLOBAL|SESSION] VARIABLES
summary	TiDB 数据库中 SHOW [GLOBAL|SESSION] VARIABLES 的使用概况。
aliases	/docs-cn/dev/sql-statements/sql-statement-show-variables/ /docs-cn/dev/reference/sql/statements/show-variables/

SHOW [GLOBAL|SESSION] VARIABLES

SHOW [GLOBAL|SESSION] VARIABLES 语句用于显示 GLOBAL 或 SESSION 范围的变量列表。如果未指定范围，则应用默认范围 SESSION。

语法图

ShowVariablesStmt ::=
    "SHOW" ("GLOBAL" | "SESSION")? VARIABLES ShowLikeOrWhere?

ShowLikeOrWhere ::=
    "LIKE" SimpleExpr
|   "WHERE" Expression

示例

以下示例展示了如何使用 SHOW [GLOBAL|SESSION] VARIABLES 语句查看变量名或变量值符合特定模式的变量。关于这些变量的详细说明，参见系统变量和语法。

{{< copyable "sql" >}}

SHOW GLOBAL VARIABLES LIKE 'tidb_stmt_summary%';

+-------------------------------------+---------------------+
| Variable_name                       | Value               |
+-------------------------------------+---------------------+
| tidb_stmt_summary_enable_persistent | OFF                 |
| tidb_stmt_summary_file_max_backups  | 0                   |
| tidb_stmt_summary_file_max_days     | 3                   |
| tidb_stmt_summary_file_max_size     | 64                  |
| tidb_stmt_summary_filename          | tidb-statements.log |
| tidb_stmt_summary_history_size      | 24                  |
| tidb_stmt_summary_internal_query    | OFF                 |
| tidb_stmt_summary_max_sql_length    | 4096                |
| tidb_stmt_summary_max_stmt_count    | 3000                |
| tidb_stmt_summary_refresh_interval  | 1800                |
+-------------------------------------+---------------------+
10 rows in set (0.001 sec)

{{< copyable "sql" >}}

SHOW GLOBAL VARIABLES LIKE 'time_zone%';

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

SHOW VARIABLES WHERE Variable_name="tidb_window_concurrency";

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

SHOW VARIABLES WHERE Value=300;

+--------------------------------+-------+
| Variable_name                  | Value |
+--------------------------------+-------+
| ddl_slow_threshold             | 300   |
| delayed_insert_timeout         | 300   |
| innodb_purge_batch_size        | 300   |
| key_cache_age_threshold        | 300   |
| slave_checkpoint_period        | 300   |
| tidb_slow_log_threshold        | 300   |
| tidb_wait_split_region_timeout | 300   |
+--------------------------------+-------+
7 rows in set (0.00 sec)

MySQL 兼容性

SHOW [GLOBAL|SESSION] VARIABLES 语句与 MySQL 完全兼容。如发现任何兼容性差异，请尝试 TiDB 支持资源。

另请参阅

• SET [GLOBAL|SESSION]