1、从mysql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mysql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（mysql 版本小于5.0在5.0中是可以的）
附：上述语句运行的环境 mysql 4.0.2以上
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