表a和表b,都有一个叫id的字段。
请问现有两个SQL语句:
delete from a where id in (select b.id from b left join a on b.id=a.id)
和 delete from a where id in (select b.id form b)
请问结果是否完全一样。我认为是一样的,再问两语句有何区别
感谢大家,如表A有几十万的记录,表B有几万的记录。现在有三种SQL语句:
1.delete from a where id in (select b.id from b left join a on b.id=a.id)
2.delete from a where id in (select b.id form b)
3.delete from a where id in (select b.id from b inner join a on b.id=a.id)
哪个语句更快些,性能更好些,因为两表的记录比较多