SQL语句：感觉很简单的问题，可是我不会~请帮忙

declare @a table(a1 int,a2 money,a3 money)

insert into @a select 1,10,0.5

insert into @a select 2,20,0

insert into @a select 3,5,5



declare @b table(a1 int,b2 money,b3 money)

insert into @b select 1,1.5,0.5

insert into @b select 1,5.5,0.5

insert into @b select 3,6,5





select a.a1,a2-isnull(b2,0)

from @a a left join 

(select a1,sum(b2)b2 from @b group by a1) b

on a.a1=b.a1

create table #a

(

	a1 float,

	a2 float,

	a3 float 

)



create table #b

(

	b1 float,

	b2 float,

	b3 float 

)



insert #a select 1  ,10  ,0.5 

insert #a select 2  ,20  ,0 

insert #a select 3  ,5   ,5



insert #b select 1 , 1.5 , 0.5

insert #b select 1 , 5.5 , 0.5

insert #b select 3,6,5

go

select #a.a1,sum(#a.a2)-isnull((select sum(b2) from #b where b1=#a.a1 group by b1),0) from #a

group by #a.a1

select a.a1,a.a2-b.b2 from a left join (select a1,sum(b2) from b group by a1) b on a.a1=b.a1