SQL中使用update inner join和delete inner join;Oracle delete join替代方案

来源:清泛编译     2017-03-28 11:02:45    人气:     我有话说( 0 人参与)

清泛网(www.tsingfun.com):UpdateUpdate 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...

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.

例子:
Sql代码

update tb_User  
set pass=''   --此处pass前不要加 tb_User 别名usr
from tb_User usr  
inner join tb_Address addr on usr.nAddressFK = addr.nAddressID  
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

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

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

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

Sql代码

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


Oracle的delete与join如何使用


delete from A where sid in
(select a.sid from A a inner join B b on a.num2 = b.num1
where b.num2 not between '10'and '10000') 这段sql如何优化,不使用in?

1. 用exists  来替代 in  

delete from where exists

(select from B b where A.num2 = b.num1

where 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。


SQL update delete join oracle

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