问下这个SQL的写法,该如何处理

问下这个SQL的写法

本帖最后由 u011669689 于 2013-09-25 18:25:00 编辑 基础条件：
user表  userid ,username 
user_money 表  u_id,user_money
user_money_exchange  表：money ,username,ordertag =1或2

现在想执行：

update user_money set user_money =  (user_money_exchange   当ordertag =1的 sum(money) + 当ordertag =2的 sum(money)） where  user_money.u_id = user.userid

<br />
update user_money <br />
set user_money.money = <br />
<br />
(select sum(ume.money) as m , u.userid from user_money_exchange ume  left join user u on ume.username = u.username where ume.ordertag = 1 group by ume.username<br />
 + <br />
select sum(ume.money) as m , u.userid from user_money_exchange ume  left join user u on ume.username = u.username where ume.ordertag = 2 group by ume.username) <br />
<br />
where user_money.u_id = u.userid<br />
<br />

这个是错的，想知道对的是？谢谢各位了

sql select update

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------解决方案--------------------
试试

update user_money um left join user u on um.u_id=u.userid<br />
left join  <br />
(select username,sum(money) as moneys from user_money_exchange group by username) ume<br />
on ume.username=u.username<br />
set um.money = ume.moneys