mysql 查两个表之间的数据差集
SELECT mailbox_id FROM `co_user` left join (select mailbox_id as i from core_mailbox) as t1 on co_user.mailbox_id= t1.i where t1.i is NULL;
SELECT mailbox_id FROM `co_user` left join (select mailbox_id as i from core_mailbox) as t1 on co_user.mailbox_id= t1.i where t1.i is NULL;