查询: exists、in、not in 和 not exists

如今两个表`user`和`user_role`表:mysql user: sql   user_role:code 1. 如今须要用 exists 做用子查询来查`user`表blog mysql> select * from user t where exists (select * from user_role r where t.id = r.user_id); 2. 咱们也能够用 in 来

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