SQL中使用update inner join和delete inner join

SQL中使用update inner join和delete inner join.

Update

Update XXX set XXX where 这种写法大家肯定都知道，才发现update和delete居然支持inner join的update方式，这个在表间关联来做更新和删除操作非常有用.

列子:

Sql代码

1. update tb_User  
2. set pass=''  
3. from tb_User usr  
4. inner join tb_Address addr on usr.nAddressFK = addr.nAddressID  
5. where usr.id=123  

update的格式是

update t1 set t1.name=’Liu’ from t1 inner join t2 on t1.id = t2.tid

MYSQL，ACCESS 写法如下:

Sql代码

1. UPDATE mem_world AS mw1 INNER JOIN mem_world   AS   mw2    
2. ON   mw1.parentid = mw2.wid   
3. SET mw1.level = mw2.level    
4. WHERE mw2.baseid = 107    
5. AND   mw2.parentid = 0    
6. AND   mw2.size > 1;  

on是表连接的筛选条件
就是说，表连接后，会产生一个类似于临时的视图这么一个东西
where是从这个临时的视图中筛选数据的
所以，你首先要搞清，你的所谓的2个条件属于哪一种

Delete

delete 语句也是类似

delete from t1 from t1 inner join t2 on t1.id = t2.tid

注意蓝色部分。

mysql:

Sql代码

1. DELETE mwb FROM   mem_world_building AS mwb INNER JOIN mem_world AS mw  
2. ON mwb.wid = mw.wid  
3. where mw.type between 11 and 15   
4. and baseid = 107   
5. and mw.parentid <> 0   
6. and   mw.size > 1;  

下面是ORACLE的:

 

Sql代码

1. DELETE TABLE1 where KHID exists ( select KHID from table2 where FWDWID=8)  

 

Sql代码

1. DELETE TABLE1 where exists ( select 1 from table2 where and table1.khid=table2.khid and FWDWID=8);