如何解决You can’t specify target table for update in FROM clause错误

mysql中You can’t specify target table for update in FROM clause错误的意思是说，不能先select出同一表中的某些值，再update这个表(在同一语句中)。 例如下面这个sql：

delete from target_info_day where id in (select min(id) as id from target_info_day where server_id = 3 group by int_time having count(target_number) > 1)

解决办法： 将select出的结果再通过中间表select一遍，这样就规避了错误。注意，这个问题只出现于mysql，mssql和oracle不会出现此问题。 将上面的sql修改为：

delete from target_info_day where id in ( select v2.id from ( select min(v1.id) as id from target_info_day v1 where v1.server_id = 3 group by v1.int_time having count(v1.target_number) > 1) v2)