SQL Server: How to Efficiently Handle Recursive CTE for Hierarchical Data with Depth Limitation
I'm working on a SQL Server 2019 database where I need to query hierarchical data using a Common Table Expression (CTE) to retrieve a tree structure of categories with a depth limitation. My current query is returning all levels of hierarchy, which is not what I need. I want to limit the result to a specific depth, say 3 levels deep, but I'm not sure how to achieve that. Here's what I have so far: ```sql WITH CategoryCTE AS ( SELECT Id, Name, ParentId, 1 AS Level FROM Categories WHERE ParentId IS NULL UNION ALL SELECT c.Id, c.Name, c.ParentId, Level + 1 FROM Categories c INNER JOIN CategoryCTE cte ON cte.Id = c.ParentId ) SELECT * FROM CategoryCTE WHERE Level <= 3; ``` Even though I've added the `WHERE Level <= 3` clause, my query still seems to be returning all the rows instead of limiting to the desired depth. I'm also concerned about performance since the `Categories` table can grow large in the future, and my current approach might not be scalable. I've tried modifying the `WHERE` clause in different places, such as inside the CTE itself, but that resulted in syntax errors or incorrect results. Additionally, I've looked into adding a termination condition to the recursive CTE, but I couldn't find a proper implementation example. Can anyone suggest how to properly limit the depth of a recursive CTE in SQL Server while ensuring that it remains performant? Any best practices or examples would be greatly appreciated!