mysql 小知识

1.http://www.cnblogs.com/liusonglin/p/4387543.html

 

Mysql: Table *** is specified twice, both as a target for 'UPDATE' and as a separate source for data

mysql在执行删除、更新的时候，可能会出现这样的错误，好比你写了相似下面的sql：

UPDATE MYTABLE SET COL=COL+1 WHERE ID IN (SELECT ID FROM MYTABLE WHERE OTHERCOL=0)

or

DELETE FROM MYTABLE WHERE ID IN (SELECT ID FROM MYTABLE WHERE OTHERCOL=0)

这个时候就会出现Table 'xxx' is specified twice这样的错误，不知道mysql为何会作这样的冻结，知道的大神请给个连接。

要解决这个问题很简单，既然table 'xxx'不能放到子查询里面，那就作一个缓存表呗。

1	DELETE FROM MYTABLE WHERE ID IN (SELECT * FROM (SELECT ID FROM MYTABLE WHERE OTHERCOL=0) AS TEMP)

　这样就没有问题了。