implementing recursive CTE performance when querying large datasets in T-SQL
I'm getting frustrated with After trying multiple solutions online, I still can't figure this out. I'm working with important performance optimization when using a recursive Common Table Expression (CTE) to retrieve hierarchical data from a large dataset in SQL Server 2019. My CTE is designed to traverse a parent-child relationship within a 'Categories' table that has over a million rows. The query seems to execute for an extended period, and I often get a timeout behavior when trying to fetch deeper levels of the hierarchy. Here's a simplified version of my CTE: ```sql WITH RecursiveCTE AS ( SELECT CategoryID, ParentID, CategoryName FROM Categories WHERE ParentID IS NULL UNION ALL SELECT c.CategoryID, c.ParentID, c.CategoryName FROM Categories c INNER JOIN RecursiveCTE r ON c.ParentID = r.CategoryID ) SELECT * FROM RecursiveCTE; ``` I've tried adding an index on the 'ParentID' column, but it hasn’t made a noticeable difference. Additionally, I’ve considered using the `OPTION (MAXRECURSION n)` hint, but I'm concerned that it might mask the underlying performance optimization instead of resolving them. When the recursion depth is substantial, the execution plan indicates a lot of logical reads, which makes me suspect that my approach isn't efficient for larger hierarchies. Are there any best practices for optimizing recursive CTEs, or alternative methods that could yield better performance? Any insight into managing or restructuring this query would be greatly appreciated. This is part of a larger CLI tool I'm building. What am I doing wrong? This is part of a larger mobile app I'm building. What am I doing wrong? I'm using Sql 3.10 in this project.