sql 编写顺序及执行顺序
没有什么问题是一口甜食解决不了的；如果解决不了再吃一口。
一、sql编写顺序
1、SELECT DISTINCT
<select list>
2、FROM
<left_table><join_type>
3、JOIN
<right_table> ON <join_condition>
4、WHERE
<where_condition>
5、GROUP BY
<group_by_list>
6、HAVING
<having_condition>
7、ORDER BY
<order_by_condition>
8、LIMIT
<limit_params>
二、sql执行顺序
1、FROM
<left_table>
2、ON
<join_condition>
3、<join_type> JOIN <right_table>
4、WHERE
<where_condition>
5、GROUP BY
<group_by_list>
6、HAVING
<having_condition>
7、SELECT DISTINCT
<select list>
8、ORDER BY
<order_by_condition>
9、LIMIT
<limit_params>
清除数据库执行时间较长的任务
SELECT * FROM information_schema.`PROCESSLIST` WHERE TIME > 1000 AND USER = dimsusr ORDER BY TIME DESC; kill id ；
