MySQL命令行

• 查看进程列表：show processlist; Sleep表示当前有一个空闲连接

  mysql> show processlist;
  +----+------+-----------------+----------+---------+------+----------+------------------+
  | Id | User | Host            | db       | Command | Time | State    | Info             |
  +----+------+-----------------+----------+---------+------+----------+------------------+
  | 34 | root | localhost:62974 | NULL     | Query   |    0 | starting | show processlist |
  | 35 | root | localhost:62979 | cmsdbdev | Sleep   |    2 |          | NULL             |
  +----+------+-----------------+----------+---------+------+----------+------------------+
  2 rows in set (0.00 sec)
  

• 查看参数：show variables like 'wait%'; 等待超时时间默认是8小时，超过此值客户端就会被断开

  mysql> show variables like 'wait%';
  +---------------+-------+
  | Variable_name | Value |
  +---------------+-------+
  | wait_timeout  | 28800 |
  +---------------+-------+
  1 row in set, 1 warning (0.00 sec)
  

• 修改参数：set wait_timeout = 60; 修改变量的值

  • 默认修改的参数只对当前会话起作用，相当于 set SESSION
  • 如果需要修改全局，使用 set GLOBAL

  mysql> set wait_timeout = 60;
  Query OK, 0 rows affected (0.00 sec)
  
  mysql> show variables like 'wait%';
  +---------------+-------+
  | Variable_name | Value |
  +---------------+-------+
  | wait_timeout  | 60    |
  +---------------+-------+
  1 row in set, 1 warning (0.00 sec)
  
  ## 全局修改，对当前会话不起作用，对新创建的会话起作用
  mysql> set GLOBAL wait_timeout = 60;
  Query OK, 0 rows affected (0.00 sec)
  
  mysql> show variables like 'wait%';
  +---------------+-------+
  | Variable_name | Value |
  +---------------+-------+
  | wait_timeout  | 28800 |
  +---------------+-------+
  1 row in set, 1 warning (0.00 sec)
  
  ## 重新打开一个会话
  

  超过一分钟后，再次查询，报错了：

  mysql> show variables like 'wait%';
  ERROR 2013 (HY000): Lost connection to MySQL server during query