SQL Server: Challenges with Dynamic Pivot Tables and Handling NULLs in Aggregation
I'm working on a SQL Server 2019 project where I need to create a dynamic pivot table from a sales dataset. My goal is to summarize total sales by product category for each month. However, I'm encountering issues with NULL values, causing the pivot results to display as NULL instead of 0, which is not ideal for my reporting needs. Here's the query I wrote to generate the pivot table: ```sql DECLARE @cols AS NVARCHAR(MAX), @query AS NVARCHAR(MAX); SELECT @cols = STRING_AGG(QUOTENAME(MONTH(SaleDate)), ',') FROM (SELECT DISTINCT MONTH(SaleDate) AS SaleMonth FROM Sales) AS Months; SET @query = 'SELECT ProductCategory, ' + @cols + ' FROM (SELECT ProductCategory, MONTH(SaleDate) AS SaleMonth, SaleAmount FROM Sales) AS SourceTable PIVOT (SUM(SaleAmount) FOR SaleMonth IN (' + @cols + ')) AS PivotTable'; EXEC sp_executesql @query; ``` When I run this, the resulting pivot table shows NULL for months where no sales occurred for a particular category. I've tried using `ISNULL` and `COALESCE` on the SUM function, but it doesn't seem to affect the pivot result. Here’s one attempt: ```sql SET @query = 'SELECT ProductCategory, ' + @cols + ' FROM (SELECT ProductCategory, MONTH(SaleDate) AS SaleMonth, ISNULL(SUM(SaleAmount), 0) AS TotalSales FROM Sales GROUP BY ProductCategory, MONTH(SaleDate)) AS SourceTable PIVOT (SUM(TotalSales) FOR SaleMonth IN (' + @cols + ')) AS PivotTable'; ``` This still results in NULLs in the pivoted output. I've also considered whether the issue might stem from the way I'm aggregating the data before pivoting. Any suggestions on how to ensure that months with no sales result in a 0 instead of NULL? Additionally, could this problem be related to how SQL Server handles NULL values during the aggregation phase? I'm eager to hear if anyone has faced a similar challenge and what approach you took to resolve it.