菜鸟问题，解决后给分

[lxjian2008]

有一个表，表结构如下：
a varchar(20);
b varchar(20);
c numeric(9);
d numeric(9);
数据例如
a b c d

A f 3.50 6.90
B f 8.33 5.64
C d 13.20 15.63

根据b字段汇总输出c-d大于0的记录数，c-d小于0的记录数，以及c不等于d的记录数，语句怎么写，谢谢！

[xeqtr1982]

declare @T table(a varchar(20),b varchar(20),c numeric(9),d numeric(9))
insert into @t select 'A','f',3.50,6.90
union all select 'B','f',8.33,5.64
union all select 'C','d',13.20,15.63

select [c-d>0]=sum(case when c-d>0 then 1 else 0 end),
[c-d<0]=sum(case when c-d<0 then 1 else 0 end),
[c<>d]=sum(case when c<>d then 1 else 0 end)
from @t

[xeqtr1982]

declare @T table(a varchar(20),b varchar(20),c numeric(9),d numeric(9))
insert into @t select 'A','f',3.50,6.90
union all select 'B','f',8.33,5.64
union all select 'C','d',13.20,15.63

select b,
[c-d>0]=sum(case when c-d>0 then 1 else 0 end),
[c-d<0]=sum(case when c-d<0 then 1 else 0 end),
[c<>d]=sum(case when c<>d then 1 else 0 end)
from @t
group by b

--少看了个条件，根据b字段

[云中客]

楼上正解,应该有GROUP BY B,否则不能分类汇总