如何删除MySQL中的所有孤立记录? [英] How to delete all orphan records in MySQL?

问题描述

我有3个表MySQL(MyIsam):

I have 3 tables MySQL (MyIsam):

user (id), message (id, userId, ...), archivedMessage (id, userId, ...)

如何删除所有没有消息且没有archivedMessage的用户?

How can I delete all the users having no message AND no archivedMessage?

推荐答案

您可以使用not exists:

delete from user
where not exists (select * from message m where m.userid = user.id)
      and not exists (select * from archivedMessage am where am.userid = user.id)

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