update的问题

[lsqzx000]

t1结构
jh xjxh tgmc tggc xs
BK 0 a 5 5.00
BK 1 a 5 5.00
BK 2 a 5 5.00
BK 3 a 5 5.00
BK 5 a 5 5.00

UPDATE t1 SET XS=
(SELECT XS FROM
(select JH,XJXH,TGMC,
(
select SUM(isnull(TGGC,0)) from t1 b where B.jh=t1.jh and t1.xjxh>=B.xjxh AND B.XJXH>0 AND t1.TGMC=B.TGMC
)
+
(SELECT XS FROM t1 C WHERE t1.JH=C.JH AND C.XJXH=0 AND C.TGMC=t1.TGMC
) AS XS from t1
) AS T_XS
WHERE t1.JH=T_XS.JH AND t1.XJXH=T_XS.XJXH AND t1.TGMC=T_XS.TGMC
)
WHERE XJXH>0
运行结果如下
jh xjxh tgmc xs
BK 0 a 5.00
BK 1 a 10.00
BK 2 a 15.00
BK 3 a 20.00
BK 5 a 25.00

我想问下 这里update是如何更新的？请详细说下过程

[ojuju10]

ding

[dawugui]

不用这么麻烦,用个累计即可.

[lsqzx000]

我只是想知道这句update是如何执行的

[dawugui]

create table tb(jh varchar(10), xjxh int, tgmc varchar(10), tggc int , xs decimal(18,2))
insert into tb values('BK', 0, 'a', 5 , 5.00 )
insert into tb values('BK', 1, 'a', 5 , 5.00 )
insert into tb values('BK', 2, 'a', 5 , 5.00 )
insert into tb values('BK', 3, 'a', 5 , 5.00 )
insert into tb values('BK', 5, 'a', 5 , 5.00 )
go
--查询
select jh,xjxh,tgmc,xs = (select sum(xs) from tb where jh = t.jh and xjxh <= t.xjxh) from tb t
/*
jh         xjxh        tgmc       xs
---------- ----------- ---------- ---------------------------------------
BK         0           a          5.00
BK         1           a          10.00
BK         2           a          15.00
BK         3           a          20.00
BK         5           a          25.00

(5 行受影响)
*/


--更改
update tb set xs = (select sum(xs) from tb where jh = t.jh and xjxh <= t.xjxh) from tb t
select * from tb
/*
jh         xjxh        tgmc       tggc        xs
---------- ----------- ---------- ----------- ---------------------------------------
BK         0           a          5           5.00
BK         1           a          5           10.00
BK         2           a          5           15.00
BK         3           a          5           20.00
BK         5           a          5           25.00

(5 行受影响)
*/

drop table tb

[dawugui]

如果你还需要tgmc,tggc这两个字段的条件,自己加上即可.

[lsqzx000]

select sum(xs) from tb where jh = t.jh and xjxh <= t.xjxh
这句产生的数据是什么样的？
是计算一次sum,更新一次？
还是全部计算出来，再更新？

[dawugui]

根据当前行,找符合记录的SUM(xs)

[lsqzx000]

那就是 计算一次sum,更新一次啦

[utpcb]

不用这么麻烦,用个累计即可.

[kaikai_kk]

LZ语句,应该是统计tggc列和值,更新到xs中,若tggc不全相等,则老乌龟答案就不对了

declare  @tb table(jh varchar(10), xjxh int, tgmc varchar(10), tggc int , xs decimal(18,2))
insert into @tb values('BK', 0, 'a', 5 , 5.00 )
insert into @tb values('BK', 1, 'a', 6 , 5.00 )
insert into @tb values('BK', 2, 'a', 8 , 5.00 )
insert into @tb values('BK', 3, 'a', 10 , 5.00 )
insert into @tb values('BK', 5, 'a', 12 , 5.00 )


--更新
update @tb set xs=(select sum(tggc) from @tb where jh=t.jh and xjxh<=t.xjxh)  from @tb t

--查询
select * From @tb

/*

BK 0	a	5	5.00	
Bk 1	a	6	11.00	
BK 2	a	8	19.00	
BK 3	a	10	29.00	
Bk 5	a	12	41.00	

*/

[ojuju10]

每一次只更新一行