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DElEtE join

首先你必须得指明你删除哪个表中的数据 DELETE Works FROM c_works Works JOIN c_works_attach Works_attach ON Works_attach.wid=Works.id JOIN c_works_image Works_image ON Works_image.wid=Works.id WHERE ( Works.id = 1 ) 其次,sql serv...

1. 用exists 来替代 in delete from A where exists(select 1 from B b where A.num2 = b.num1where b.num2 not between '10' and '10000');不过你用not between,估计效率就不怎么好了。 2. 在 A 的num2,B的num1、num2上都 建立索引。

例如三个表A,B,C的关联: 如果B的二级数据或C的二级数据不一定存在,用以下语句: delete A,B,C from A left join B on B.id_b=A.id left join C on C.id_c=A.id where (B.id_b=A.id) or (C.id_c=A.id); 删除3个表都存在的关联数据: delete A,B...

可以 例如: 1 update: update dept set dname = 'ORACLE' where deptno in (select a.deptno from emp a left join dept b on a.deptno = b.deptno); 2 delete: delete dept where deptno in (select a.deptno from emp a left join dept b on ...

有必要吗,这个查询条件的话,用这种写法就可以,left join 的话优势发挥不出来

您好,这个是可以的,其实他们的用法和select的一样,只不过是前面的部分是update;后面的是set 后面的where语句都是通用的。 首先看你要删除多少行?? 如果删除的行数不多的话,比如就删除几十万行,tb1.id有索引,应该不会很慢,直接扫描索引...

delete from table1 a where exists (select 1 from table2 b where a.id=b.id)

请别使用(或获取)用于删除、增加或者结合东西的服务器。 add是增加的意思,join是把一个东西结合,或者加到另一个东西里面。

你要是只要删除ss表 中的数据 直接用以下的方法就可以了 delete ss from dbo.Login ss inner join Server gs on ss.ServerId=gs.ServerId inner join Area ga on gs.AreaId=ga.AreaId inner join Game g on ga.GameId=g.GameID where g.GameId=5...

delete from A left join B on A.GUID=B.GUID where B.GUID is null 不考虑性能就用IN咯,比上一条要短一点 delete from A where GUID not in (select GUID from B)

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