“delete from table 呀”“怪不得，其实要删除MySQL数据是有好几种方式的，有些场景下是不应该用DELETE的，比如你这种情况。 好了，让我来给你讲一下 ...

Yes. Foreign keys can refer to another column in the same table. The top-level folder might need to be its own parent - I don't know if it'll let you have a NULL there. As long as the interface ...