How to optimize a recursive CTE for hierarchical data retrieval in T-SQL?
I'm optimizing some code but I'm sure I'm missing something obvious here, but I am working with SQL Server 2019, and I am trying to retrieve hierarchical data using a recursive Common Table Expression (CTE)... The CTE is fetching a tree structure from a table that contains parent-child relationships. However, I am working with performance optimization when the hierarchy is deep, as the query takes an excessive amount of time to execute. Here’s the CTE I’ve implemented: ```sql WITH RecursiveCTE AS ( SELECT Id, Name, ParentId, 0 AS Depth FROM MyTable WHERE ParentId IS NULL UNION ALL SELECT m.Id, m.Name, m.ParentId, r.Depth + 1 FROM MyTable m INNER JOIN RecursiveCTE r ON m.ParentId = r.Id ) SELECT * FROM RecursiveCTE ORDER BY Depth, Name; ``` I’ve tried indexing the `ParentId` column, but it doesn’t seem to have made a important difference in performance. I also considered switching to a different approach using a temporary table, but I’m not sure if that would help with tree depth issues or if it would complicate my code unnecessarily. The current execution plan shows a lot of recursive operator calls, which raises concerns about efficiency. Is there a more optimized way to handle deep hierarchical queries in T-SQL? Any recommendations on indexing strategies or alternative query patterns would be greatly appreciated. I’m particularly interested in solutions that can improve performance without sacrificing readability and maintainability of the code. Thanks in advance for your help! Has anyone else encountered this? This issue appeared after updating to Sql LTS. The project is a microservice built with Sql. Has anyone else encountered this?