一个关于累加的问题（百分题）

Question

select id,in1,out1,qty=isnull((select sum(in1) from tb where id<a.id),0)+in1-out1 from tb a

Answer 1

select 
    a.ID,a.In,a.Out,Qty=sum(b.In-b.Out) 
from 
    Balance a,Balance b 
where 
    a.ID>=b.ID 
group by 
    a.ID,a.In,a.Out

Answer 2

select 
    a.ID,a.In,a.Out,Qty=sum(b.In-b.Out) 
from 
    Balance a,Balance b 
where 
    a.ID>=b.ID 
group by 
    a.ID,a.In,a.Out

Answer 3

select 
    a.ID,a.In,a.Out,Qty=(select sum(b.In-b.Out) from Balance where ID<=a.ID) 
from 
    Balance a

Answer 4

select 
    a.ID,a.In,a.Out,Qty=(select sum(b.In-b.Out) from Balance where ID<=a.ID) 
from 
    Balance a
对 我还考虑少了些问题

Answer 5

select B.*,(select sum(In-Out) from Balance where id<=B.id) as Qty
from Balance B

Answer 6

select id,in1,out1,
qty=isnull((select top 1 Qty from tb where id<a.id order by ID desc),0)+in1-out1 from tb a