Calculate a Running Total in SQL Server

Asked 2009-05-13T23:42:26.890

200

Imagine the following table (called TestTable):

id     somedate    somevalue
--     --------    ---------
45     01/Jan/09   3
23     08/Jan/09   5
12     02/Feb/09   0
77     14/Feb/09   7
39     20/Feb/09   34
33     02/Mar/09   6

I would like a query that returns a running total in date order, like:

id     somedate    somevalue  runningtotal
--     --------    ---------  ------------
45     01/Jan/09   3          3
23     08/Jan/09   5          8
12     02/Feb/09   0          8
77     14/Feb/09   7          15  
39     20/Feb/09   34         49
33     02/Mar/09   6          55

I know there are various ways of doing this in SQL Server 2000 / 2005 / 2008.

I am particularly interested in this sort of method that uses the aggregating-set-statement trick:

INSERT INTO @AnotherTbl(id, somedate, somevalue, runningtotal) 
   SELECT id, somedate, somevalue, null
   FROM TestTable
   ORDER BY somedate

DECLARE @RunningTotal int
SET @RunningTotal = 0

UPDATE @AnotherTbl
SET @RunningTotal = runningtotal = @RunningTotal + somevalue
FROM @AnotherTbl

... this is very efficient but I have heard there are issues around this because you can't necessarily guarantee that the UPDATE statement will process the rows in the correct order. Maybe we can get some definitive answers about that issue.

But maybe there are other ways that people can suggest?

edit: Now with a SqlFiddle with the setup and the 'update trick' example above

Edit Report

2 Answers

While Sam Saffron did great work on it, he still didn't provide recursive common table expression code for this problem. And for us who working with SQL Server 2008 R2 and not Denali, it's still fastest way to get running total, it's about 10 times faster than cursor on my work computer for 100000 rows, and it's also inline query.
So, here it is (I'm supposing that there's an ord column in the table and it's sequential number without gaps, for fast processing there also should be unique constraint on this number):

;with 
CTE_RunningTotal
as
(
    select T.ord, T.total, T.total as running_total
    from #t as T
    where T.ord = 0
    union all
    select T.ord, T.total, T.total + C.running_total as running_total
    from CTE_RunningTotal as C
        inner join #t as T on T.ord = C.ord + 1
)
select C.ord, C.total, C.running_total
from CTE_RunningTotal as C
option (maxrecursion 0)

-- CPU 140, Reads 110014, Duration 132

sql fiddle demo

update I also was curious about this update with variable or quirky update. So usually it works ok, but how we can be sure that it works every time? well, here's a little trick (found it here - http://www.sqlservercentral.com/Forums/Topic802558-203-21.aspx#bm981258) - you just check current and previous ord and use 1/0 assignment in case they are different from what you expecting:

declare @total int, @ord int

select @total = 0, @ord = -1

update #t set
    @total = @total + total,
    @ord = case when ord <> @ord + 1 then 1/0 else ord end,
    ------------------------
    running_total = @total

select * from #t

-- CPU 0, Reads 58, Duration 139

                        
                        
                            answered 2012-12-06T13:23:07.293


            
            
                
                    
                        
                            
                            
                        
                        1
                        
                            
                            
                        
                        
                    
                    
                        
                        I believe a running total can be achieved using the simple INNER JOIN operation below.

SELECT
     ROW_NUMBER() OVER (ORDER BY SomeDate) AS OrderID
    ,rt.*
INTO
    #tmp
FROM
    (
        SELECT 45 AS ID, CAST('01-01-2009' AS DATETIME) AS SomeDate, 3 AS SomeValue
        UNION ALL
        SELECT 23, CAST('01-08-2009' AS DATETIME), 5
        UNION ALL
        SELECT 12, CAST('02-02-2009' AS DATETIME), 0
        UNION ALL
        SELECT 77, CAST('02-14-2009' AS DATETIME), 7
        UNION ALL
        SELECT 39, CAST('02-20-2009' AS DATETIME), 34
        UNION ALL
        SELECT 33, CAST('03-02-2009' AS DATETIME), 6
    ) rt

SELECT
     t1.ID
    ,t1.SomeDate
    ,t1.SomeValue
    ,SUM(t2.SomeValue) AS RunningTotal
FROM
    #tmp t1
    JOIN #tmp t2
        ON t2.OrderID <= t1.OrderID
GROUP BY
     t1.OrderID
    ,t1.ID
    ,t1.SomeDate
    ,t1.SomeValue
ORDER BY
    t1.OrderID

DROP TABLE #tmp


                        
                        
                            answered 2011-02-03T18:38:35.567



        
        
            Your Answer