MySQL wait_timeout变量 - GLOBAL vs SESSION [英] MySQL wait_timeout Variable - GLOBAL vs SESSION

问题描述

  SHOW VARIABLES LIKE％wait％
 
结果：28800 
 
 SET @@ GLOBAL.wait_timeout = 300 
 
显示全局变量，如％wait％
 
结果：300 
 
显示会话变量如％wait％
 
结果：28800 
  

我对结果感到困惑。为什么最后一个查询会给出结果：28800？

解决方案

您的会话状态是在开始会话后设置的，默认情况下，如果您在 SET @@ GLOBAL.wait_timeout = 300 之后断开连接，则请取消当前的GLOBAL值。 然后重新连接，你会看到

  SHOW SESSION VARIABLES LIKE％wait％; 
 
结果：300 
  

同样， / p>

  mysql> SET session wait_timeout = 300; 
  

您会得到

 的MySQL> SHOW SESSION VARIABLES Like'wait_timeout'; 
 
 + --------------- + ------- + 
 |变量名|值| 
 + --------------- + ------- + 
 | wait_timeout | 300 | 
 + --------------- + ------- + 
  

SHOW VARIABLES LIKE "%wait%"

Result: 28800

SET @@GLOBAL.wait_timeout=300

SHOW GLOBAL VARIABLES LIKE "%wait%"

Result: 300

SHOW SESSION VARIABLES LIKE "%wait%"

Result:28800

I am confused by the results. Why does the last query give Result:28800 ?

解决方案

Your session status are set once you start a session, and by default, take the current GLOBAL value.

If you disconnected after you did SET @@GLOBAL.wait_timeout=300, then subsequently reconnected, you'd see

SHOW SESSION VARIABLES LIKE "%wait%";

Result: 300

Similarly, at any time, if you did

mysql> SET session wait_timeout=300;

You'd get

mysql> SHOW SESSION VARIABLES LIKE 'wait_timeout';

+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| wait_timeout  | 300   |
+---------------+-------+

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