MySQL中的系统变量和用户变量
系统变量有当前会话(session)变量和全局变量, 它们都以 @@ 开头. 仅以单个@开头的变量为用户变量.
列出所有变量
mysql> show variables;
注意会列出很多.
可以使用LIKE模糊查询变量
SHOW VARIABLES LIKE "%ver%";
@@version 存储MySQL的版本
mysql> SELECT @@version;
+-----------+
| @@version |
+-----------+
| 5.5.27 |
+-----------+
1 row in set (0.00 sec)
@@tx_isolation 当前会话的事务隔离级别
mysql> SELECT @@tx_isolation\G;
*************************** 1. row ***************************
@@tx_isolation: REPEATABLE-READ
1 row in set (0.00 sec)
@@global.tx_isolation 当前会话的事务隔离级别
mysql> SELECT @@global.tx_isolation;
+-----------------------+
| @@global.tx_isolation |
+-----------------------+
| REPEATABLE-READ |
+-----------------------+
1 row in set (0.00 sec)
mysql> SHOW VARIABLES LIKE "innodb_locks_%";
+--------------------------------+-------+
| Variable_name | Value |
+--------------------------------+-------+
| innodb_locks_unsafe_for_binlog | OFF |
+--------------------------------+-------+
1 row in set (0.00 sec)