SQL 列值分組累計求和

測試數據：

create table Salary
(
UserId int,
[Month] int,
Salary decimal(13,2)
)

insert into Salary
select 10010,1,3500.40 union all
select 10010,2,3000.60 union all
select 10010,3,4000.00 union all
select 10010,4,3800.50 union all
select 10020,1,3000.50 union all
select 10020,2,3000.50 union all
select 10020,3,3500.20 union all
select 10020,4,3800.80 union all
select 10020,5,4000.00 union all
select 10018,2,4000.50 union all
select 10018,3,4500.20 union all
select 10018,4,4800.80 

查看數據：

select * from Salary

要得到的結果：

方法一：

select *,
(select sum(Salary) from Salary where UserId=s.UserId and Month<=s.Month) as Balance 
from Salary as s
order by GETDATE()

方法二：

;with cte  as 
(
select *,ROW_NUMBER() over(partition by UserId order by [Month] asc) as Rn from Salary 
),
cte1 as 
(
select *,Salary as Balance from cte where RN=1
union all
select a.UserId,a.Month,a.Salary,a.Rn,
cast((a.Salary+b.Balance) as decimal(13,2)) 
from cte as a,cte1 as b 
where a.UserId=b.UserId and a.RN=b.RN+1 
)
select UserId,[MONTH],Salary,Balance from cte1 order by UserId,[month]

方法三（很新穎）：

select *,CAST(0 as decimal(13,2)) as Balance into #Sal from Salary
declare @userid int,@amount decimal(13,2)
update s set @amount=case when s.UserId=@userid then s.Salary+@amount else s.Salary end,
@UserId=s.UserId,
s.Balance=@amount
from #Sal as s
select * from #Sal
drop table #Sal

方法四（sql server 2012以上適用）：

select *,
Sum(Salary) over(partition by UserId order by [Month] asc) as Balance
from Salary

　　列值分組求和的方法同樣也是求差的情況，只不過將分組后的非第一條數據的求差字段（如：Salary）求相反數作為一個新的字段，這樣就轉換成列值分組球和了。