Let us see how to calculate Row Totals and Running Totals in SQL Server. In the code shown below, we will first calculate the sum of Col1 and Col2 for each row and then also maintain a Running Total of the same.
Update: As williamdurkin and TheSQLGuru pointed out, the method in the T-SQL query below does not guarantee the order that the update runs in.
The correct solution is given by Jeff Moden over here http://www.sqlservercentral.com/articles/Advanced+Querying/61716/ (Requires Registration to view) . Thanks guys for the correction!
CREATE TABLE #TmpTable
ID int, Col1 int, Col2 int,
RowTotal int, RunningTotal int
INSERT INTO #TmpTable SELECT 1, 5, 2, 0, 0
INSERT INTO #TmpTable SELECT 2, 14, 65, 0, 0
INSERT INTO #TmpTable SELECT 3, 34, 22, 0, 0
INSERT INTO #TmpTable SELECT 4, 56, 22, 0, 0
INSERT INTO #TmpTable SELECT 5, 7, 23, 0, 0
QUERY (results not guaranteed)
DECLARE @rowtot int
DECLARE @runtot int
SET @rowtot = 0 -- set rowtotal to 0
SET @runtot = 0 -- set runningtotal to 0
SET RowTotal = @rowtot,
RunningTotal = @runtot,
@rowtot = COALESCE(Col1, 0) + COALESCE(Col2, 0),
@runtot = @runtot + @rowtot
SELECT * FROM #TmpTable
The code is quite easy to understand. We are maintaining two variables @rowtot (for RowTotal) and @runtot (Running Total) and use the Update Table command to update the Row Total and Running Total for each row.