Finding the running total is a common requirement in the industry when working with SQL Server. In this article, we will explore two different methods to achieve this task, one for SQL Server 2008 R2 and earlier versions, and another for SQL Server 2012 and later versions.

SQL Server 2008 R2 and Earlier Versions

In SQL Server 2008 R2 and earlier versions, finding the running total can be a bit cumbersome and inefficient. Let’s take a look at an example:

SELECT ID, Value, 
    (SELECT SUM(Value) FROM TestTable T2 WHERE T2.ID <= T1.ID) AS RunningTotal
FROM TestTable T1

This query calculates the running total by using a subquery to sum up the values for all rows with IDs less than or equal to the current row’s ID. While this method works, it can be quite expensive in terms of performance.

SQL Server 2012 and Later Versions

Fortunately, SQL Server 2012 introduced a new feature called the OVER clause with the ROWS UNBOUNDED PRECEDING option, which provides a much more efficient and cleaner way to calculate the running total. Here’s an example:

SELECT ID, Value, 
    SUM(Value) OVER (ORDER BY ID ROWS UNBOUNDED PRECEDING) AS RunningTotal
FROM TestTable

This query uses the OVER clause to calculate the running total by summing up the values for all rows preceding the current row, ordered by the ID column. This method is significantly faster and more efficient compared to the subquery approach.

Conclusion

In conclusion, if you are working with SQL Server 2012 or later versions, using the OVER clause with the ROWS UNBOUNDED PRECEDING option is the recommended way to calculate the running total. It provides better performance and cleaner code compared to the subquery method used in earlier versions.

Feel free to share any other better options or techniques you may have for finding the running total in SQL Server.