Question

I have a table like this

UserID	Score	Date
5	6	2010-1-1
7	8	2010-1-2
5	4	2010-1-3
6	3	2010-1-4
7	4	2010-1-5
6	1	2010-1-6

I would like to get a table like this

UserID	Score	RunningTotal	Date
5	6	6	2010-1-1
5	4	10	2010-1-3
6	3	3	2010-1-4
6	1	4	2010-1-6
7	8	8	2010-1-2
7	4	12	2010-1-5

Thanks!

Answer 1

Unlike Oracle, PostgreSQL and even MySQL, SQL Server has no efficient way to calculate running totals.

If you have few scores per UserID, you can use this:

SELECT  userId,
        (
        SELECT  SUM(score)
        FROM    scores si
        WHERE   si.UserID = so.UserID
                AND si.rn <= so.rn
        )
FROM    (
        SELECT  *,
                ROW_NUMBER() OVER (PARTITION BY UserID) AS rn
        FROM    scores
        ) so

, however, this will be very inefficient for larger tables.

For larger tables, you could benefit from using (God help me) a cursor.