数据库中有两张表。

DELETE cdb_posts,cdb_threads FROM cdb_posts ,cdb_threads where  cdb_threads.displayorder=-1 and cdb_posts.tid=cdb_threads.tid  DELETE  FROM cdb_posts  where tid in ( select tid from cdb_threads where  cdb_threads.displayorder=-1); delete from cdb_threads where  cdb_threads.displayorder=-1

DELETE删除多表数据，怎样才能同时删除多个关联表的数据呢？这里做了深入的解释：

1、 delete from t1 where 条件 2、delete t1 from t1 where 条件 3、 delete t1 from t1,t2 where 条件 4、delete t1,t2 from t1,t2 where 条件 前 3者是可行的，第4者不可行。 也就是简单用delete语句无法进行多表删除数据操作，不过可以建立级联删除，在两个表之间建立级联删除关系，则可以实现删除一个表的数据时，同时删除另一个表中相关的数据。 1、从数据表t1中把那些id值在数据表t2里有匹配的记录全删除 掉 DELETE t1 FROM t1,t2 WHERE t1.id=t2.id 或 DELETE FROM t1 USING t1,t2 WHERE t1.id=t2.id 2、从数据表t1里在数据表t2里没有匹配的记录查找出来并删除掉 DELETE t1 FROM t1 LEFT JOIN T2 ON t1.id=t2.id WHERE t2.id IS NULL 或 DELETE FROM t1,USING t1 LEFT JOIN T2 ON t1.id=t2.id WHERE t2.id IS NULL 3、 从两个表中找出相同记录的数据并把两个表中的数据都删除掉 DELETE t1,t2 from t1 LEFT JOIN t2 ON t1.id=t2.id WHERE t1.id=25 注意此处的delete t1,t2 from 中的t1,t2不能是别名 如：delete t1,t2 from table_name as t1 left join table2_name as t2 on t1.id=t2.id where table_name.id=25 在数据里面执行是错误的（MYSQL 版本不小于5.0在5.0中是可以的） 上述语句改 写成  

delete table_name,table2_name from table_name as t1 left join table2_name as t2 on t1.id=t2.id where table_name.id=25 在数据里面执行是错误的（ 版本小于5.0在5.0中是可以的）