It is difficult for me to write this particular article and I’ll tell you why. If you don’t care then just skip down to the example, but here goes anyway. It is very rare that you should have to perform looping in SQL. There are certain situations that do require it, and they are mostly back-end or maintenance related.
Ok, now that I got that off my chest, here you go. In order to perform an execution which iterates performing a “for each row”, this is the easiest way for me:
SELECT RowNum = ROW_NUMBER() OVER(ORDER BY CustomerID) ,* INTO #Customers FROM SalesLT.Customer DECLARE @MaxRownum int SET @MaxRownum = (SELECT MAX(RowNum) FROM #Customers) DECLARE @Iter int SET @Iter = (SELECT MIN(RowNum) FROM #Customers) WHILE @Iter <= @MaxRownum BEGIN SELECT * FROM #Customers WHERE RowNum = @Iter -- run your operation here SET @Iter = @Iter + 1 END DROP TABLE #Customers
Once again, take heed, even though this is how to loop, I encourage set-based operations whenever possible.
