T-SQL Window Function Returning Unexpected Results with Partitioning
I'm maintaining legacy code that Quick question that's been bugging me - I'm experimenting with I'm working with an scenario with a T-SQL query that uses window functions, specifically when partitioning data. I'm trying to compute a running total of sales for each product category, but the results are not what I expected. Here's the query I'm using: ```sql WITH SalesCTE AS ( SELECT ProductID, CategoryID, SaleDate, SaleAmount, SUM(SaleAmount) OVER (PARTITION BY CategoryID ORDER BY SaleDate) AS RunningTotal FROM Sales ) SELECT * FROM SalesCTE ORDER BY CategoryID, SaleDate; ``` The question occurs when I have multiple entries for the same `CategoryID` on the same `SaleDate`. In these cases, the `RunningTotal` does not seem to accumulate correctly. For example, I have two sales of $100 and $200 for `CategoryID = 1` on the same day, but the running total shows as just $100 and then $200 instead of $300 for the second entry. I've tried adding an additional column to the `ORDER BY` clause within the `SUM()` function to clarify the order: ```sql SUM(SaleAmount) OVER (PARTITION BY CategoryID ORDER BY SaleDate, ProductID) AS RunningTotal ``` However, the running total is still not behaving as expected, and I'm not sure what I'm missing. I would appreciate any insight into how to correctly compute the running total in this scenario. Is there a best practice for handling ties in the order of the partition? Additionally, I'm working with SQL Server 2019 and have already checked for updates, so that shouldn't be a factor. Any help would be greatly appreciated! Thanks, I really appreciate it! What am I doing wrong? Hoping someone can shed some light on this.