blocks|key|2721904|text|更改mysql中的系统变量值(cfr。http://dev.mysql.com/doc/refman/5.1/en/set-statement.html)不会更改已连接到会话的客户端的值。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2721905|更改将一直持续到服务器重新启动、后续更改或会话到期。|2721906|有关更多详细信息，请参阅http://bugs.mysql.com/bug.php?id=38704|2721907|entityMap|0|LINK|mutability|MUTABLE|url|http://dev.mysql.com/doc/refman/5.1/en/set-statement.html|1|http://bugs.mysql.com/bug.php?id=38704^0|J|1L|0|0|0|C|12|1|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@$A|S|B|T|1|U]]|C|$]]|$1|D|3|E|5|6|7|V|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|H|3|-4|5|6|7|10|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]|P|$5|K|L|M|C|$N|Q]]]]

Changing a system variable value in mysql (cfr. <a href="http://dev.mysql.com/doc/refman/5.1/en/set-statement.html" rel="noreferrer">http://dev.mysql.com/doc/refman/5.1/en/set-statement.html</a>) does not alter the value for clients already connected to a session.

The change will last until server reboot, subsequent changes or session expiration.

please refer <a href="http://bugs.mysql.com/bug.php?id=38704" rel="noreferrer">http://bugs.mysql.com/bug.php?id=38704</a> for more details

blocks|key|1962992|text|您正在设置全局系统变量，但查询的是会话变量。要使全局变量设置在当前会话中生效，需要重新连接或设置@@SESSION.long_query_time变量。(请注意，默认情况下显示变量会显示会话变量。)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1962993|下面是一个示例：|1962994|mysql>+SHOW+SESSION+VARIABLES+LIKE+"long_query_time";
%2B-----------------%2B-----------%2B
%7C+Variable_name+++%7C+Value+++++%7C
%2B-----------------%2B-----------%2B
%7C+long_query_time+%7C+10.000000+%7C
%2B-----------------%2B-----------%2B

mysql>+SET+@@GLOBAL.long_query_time+=+1;

mysql>+SHOW+GLOBAL+VARIABLES+LIKE+"long_query_time";
%2B-----------------%2B----------%2B
%7C+Variable_name+++%7C+Value++++%7C
%2B-----------------%2B----------%2B
%7C+long_query_time+%7C+1.000000+%7C
%2B-----------------%2B----------%2B

mysql>+SHOW+VARIABLES+LIKE+"long_query_time";
%2B-----------------%2B-----------%2B
%7C+Variable_name+++%7C+Value+++++%7C
%2B-----------------%2B-----------%2B
%7C+long_query_time+%7C+10.000000+%7C
%2B-----------------%2B-----------%2B|code-block|syntax|javascript|1962995|1962996|MySQL+8.0引入了SET+PERSIST+..语法，它可以帮助您保持动态设置的配置。请参阅MySQL+8.0+manual|offset|length|style|CODE|1962997|entityMap|0|LINK|mutability|MUTABLE|url|https://dev.mysql.com/doc/refman/8.0/en/set-variable.html^0|0|0|0|0|C|E|1C|G|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Y|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Z|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|10|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|11|8|@$L|12|M|13|N|O]]|9|@$L|14|M|15|1|16]]|A|$]]|$1|P|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|Q|$R|$5|S|T|U|A|$V|W]]]]

You are setting a GLOBAL system variable, but you querying for the SESSION variable. For the GLOBAL variable setting to take effect for the current session, you need to reconnect, or set the @@SESSION.long_query_time variable. (Note that SHOW VARIABLES by default shows the session variables.)

Here is an example:

<pre><code>mysql&gt; SHOW SESSION VARIABLES LIKE "long_query_time";
+-----------------+-----------+
| Variable_name | Value |
+-----------------+-----------+
| long_query_time | 10.000000 |
+-----------------+-----------+

mysql&gt; SET @@GLOBAL.long_query_time = 1;

mysql&gt; SHOW GLOBAL VARIABLES LIKE "long_query_time";
+-----------------+----------+
| Variable_name | Value |
+-----------------+----------+
| long_query_time | 1.000000 |
+-----------------+----------+

mysql&gt; SHOW VARIABLES LIKE "long_query_time";
+-----------------+-----------+
| Variable_name | Value |
+-----------------+-----------+
| long_query_time | 10.000000 |
+-----------------+-----------+
</code></pre>

<hr>

MySQL 8.0 introduced the <code>SET PERSIST ..</code> syntax which could help persist configuration you are setting dynamically. See the <a href="https://dev.mysql.com/doc/refman/8.0/en/set-variable.html" rel="noreferrer">MySQL 8.0 manual</a>

I am using MySQL version 5.1.66. I saw that the <a href="http://dev.mysql.com/doc/refman/5.1/en/server-system-variables.html#sysvar_long_query_time">long_query_time</a> variable is dynamic, but when I tried 

<pre><code>set GLOBAL long_query_time=1; 
</code></pre>

After the above operation again I tried

<pre><code>mysql&gt; show variables like 'long_query_time';
+-----------------+-----------+
| Variable_name | Value |
+-----------------+-----------+
| long_query_time | 10.000000 |
+-----------------+-----------+
1 row in set (0.00 sec)
</code></pre>

From the mysql console it is not getting altered , why?

Why I could not alter the variable long_query_time variable at runtime

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我使用的是MySQL版本5.1.66。我看到变量是动态的，但是当我尝试set GLOBAL long_query_time=1; 在上面的操作之后，我再次尝试mysql> show variables like 'long_query_time';+-----------------+-----------+| Var...

问为什么我不能在运行时更改变量long_query_time变量
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问为什么我不能在运行时更改变量long_query_time变量EN