T-SQL iterative current sum by column value

Question

I'm working at SQL Server 2008 R2. I'm trying to write a stored procedure which will create new column with current sum of Costs.

I have MyTable :

ID     |   Costs
----------------
1      |     5
2      |     3
3      |     2
4      |     4

but I need the third column 'CurrentCosts' with values:

ID     |   Costs   |  CurrentCosts
----------------------------------
1      |     5     |      5
2      |     3     |      8
3      |     2     |      10
4      |     4     |      14

• The first value in 'CurrentCosts' is: 5 + 0 = 5
• The second value in 'CurrentCosts' is: 5 + 3 = 8
• The third value in 'CurrentCosts' is: 8 + 2 = 10
• The fourth value in 'CurrentCosts' is: 10 + 4 = 14

and so on.

I tried with:

declare @ID INT
declare @current_cost int
declare @running_cost int

select @ID = min( ID ) from MyTable
set @running_cost = 0
set @current_cost = 0

while @ID is not null
begin
    select ID, Costs, @running_cost as 'CurrentCosts' from MyTable where ID = @ID
    select @ID = min( ID ) from MyTable where ID > @ID
    select @current_cost = Costs from MyTable where ID = @ID
    set @running_cost += @current_cost
end

It works but if anybody have better solution, I will be grateful. I got numerous tables with just one result in each and as much tables as I have SELECT commanad in loop. Is there some solution where I will get just one table with all results.

Answer 1

You could use a sub query:

SELECT ID, Costs, 
       (SELECT Sum(Costs) 
        FROM   dbo.MyTable t2 
        WHERE  t2.ID <= t1.ID) AS CurrentCosts 
FROM   dbo.MyTable t1 

Demo

ID     COSTS    CURRENTCOSTS
1        5            5
2        3            8
3        2            10
4        4            14

Answer 2

您可以找到这个有趣的http://www.sqlperformance.com/2012/07/t-sql-queries/running-totals