关于MYSQL UPDATE嵌套子查寻 IN无法更新的解决方法

更新该句

update da_question set answer_time = now()
where id in (
 select id from da_question where  answer_time is null and id  in (select distinct parent_id from da_question)
 )

 

在 MySQL 命令列工具中傳回：
ERROR 1093 (HY000): You can't specify target table 'forum_members' for update in FROM clause

 

改成下列命令處理就 可以解决无法更新的问题

update da_question a inner join ( select id from da_question where  answer_time is null and id  in (select distinct parent_id from da_question)) b on a.id=b.id set answer_time=now();