select
    @a=sum(t1.c1),
    @b=sum(CASE WHEN t2.d= 1 THEN t2.e ELSE t2.e/100 *@a end),
    @a-@b
from
    t1,t2
where 
    t1.f=t2.f

------解决方案--------------------
SQL code
declare @a as int
select @a = sum(t1.c1) from t1
declare @b as int
select @b = sum(CASE WHEN t2.d = 1 THEN t2.e ELSE t2.e/100 * @a) from t1 , t2 where t1.f=t2.f 
select @a - @b

------解决方案--------------------
SQL code
declare @a decimal(10,2),@b decimal(10,2)
select @a=sum(c1) from t1
select @b=sum(CASE WHEN t2.d= 1 THEN t2.e ELSE t2.e/100 * @a end) from t1,t2 where t1.f=t2.f
select @a-@b

------解决方案--------------------
我在4楼的是返回一个值.

------解决方案--------------------
sum只返回1行阿，你没有group，返回什么列

------解决方案--------------------
关注，学习！

------解决方案--------------------
看不懂

------解决方案--------------------

..

------解决方案--------------------
..