Delete,Update与left join

• 2010-08-21
• 3811 View

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 tb_User
set pass=''
from tb_User usr
inner join tb_Address addr on usr.nAddressFK = addr.nAddressID
where usr.id=123update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; 
UPDATE mem_world AS mw1 INNER JOIN mem_world  AS  mw2 
ON  mw1.parentid = mw2.wid
SET mw1.level = mw2.level 
WHERE mw2.baseid = 107 
AND  mw2.parentid = 0 
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; 
DELETE mwb FROM  mem_world_building AS mwb INNER JOIN mem_world AS mw
ON mwb.wid = mw.wid
where mw.type between 11 and 15
and baseid = 107
and mw.parentid <> 0
and  mw.size > 1; 
下面是ORACLE的:

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

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