SQL Server query returning NULL for aggregated columns when using COALESCE with multiple tables
I'm attempting to set up I'm migrating some code and I've searched everywhere and can't find a clear answer... I'm working with SQL Server 2019 and trying to aggregate data from multiple tables using a LEFT JOIN. My goal is to display the total sales per product, but I'm working with an scenario where some of the aggregated columns return NULL instead of 0 when there are no sales records for certain products. Here's what my query looks like: ```sql SELECT p.ProductID, p.ProductName, COALESCE(SUM(s.SaleAmount), 0) AS TotalSales FROM Products p LEFT JOIN Sales s ON p.ProductID = s.ProductID GROUP BY p.ProductID, p.ProductName; ``` When I run this query, I expected `TotalSales` to display 0 for products without any sales, but instead, I see NULL values. I've tried using `ISNULL` instead of `COALESCE`, but that doesn't fix the scenario either. I also verified that the `Sales` table indeed has rows where the `ProductID` can match, but for some products, it simply doesn't exist. Is there something I'm missing about how aggregation works with LEFT JOINs in SQL Server? Any insights would be greatly appreciated! I'm working on a CLI tool that needs to handle this. Am I missing something obvious? Thanks for taking the time to read this!