两个表的字段相减

[jinyefeng]

比如a,b表都有个字段c,我想让a表的sum(c)减去b表的sum(c)我是这样写的
selct a.sum(c)-b.sum(c) as d from a,b
没有结果，不知是什么原因

[yoki]

应该是selct sum(a.c)-sum(b.c) as d from a,b吧?

[愉快的登山者]

selct sum(a.c)-sum(b.c) as d from a,b

[愉快的登山者]

selct sum(isnull(a.c,0))-sum(isnull(b.c,0)) as d from a,b

[abcddcba]

select (select sum(c) from a) - (select sum(c) from b)

[abcddcba]

from a,b 这样是不对的，形成的结果是两个表的笛卡儿乘积

[happydreamer]

select sum(a.c)-sum(b.c) as diff from a,b

[jinyefeng]

我又做了两个视图select sum(c) as e from a
select sum(c) as f from b
又做了第三个视图select b.e-c.f from a,b结果还是出不来呢

[abcddcba]

怎么没人听我的呢？
from a,b 这样子是不行的，这样形成了全连接！！！

[New_bug]

select ((select sum(isnull(c,0)) from a as int)-(Select sum(isnull(c,0)) from b)) as Result

[New_bug]

上面的一定可以，我试过了

[New_bug]

修正一下：不好意思
select ((select sum(isnull(c,0)) from Ta )-(Select sum(isnull(c,0)) from Tb)) as Result

[jinyefeng]

我试过了还是没有结果呢

[愉快的登山者]

直接出来：
select (select sum(isnull(c,0)) from a) - (select sum(isnull(c,0)) from b)
用视图：
create view c as select sum(isnull(c,0)) as e from a
create view d as select sum(isnull(c,0)) as f from b
第三个视图select b.e-c.f from a,b这样做是不对的。
应为：
select c.e - d.f from c, d

[jinyefeng]

我想也应该出来了，不过就是不出来的。上面的登山者，我是按照后面的做的，只不过我在这里写错了，其实在sql server 上 写的和你一样的，不过就是不出来呢，真是奇怪

[jinyefeng]

出来了，原来是我的一个表里没有数据，所以出不来的。不好意思，对不起大家了

[流星尔]

hehe ,太有意思了。