SQL Server: How to Correctly Use Common Table Expressions with Recursive Queries to Avoid Infinite Loops
I'm optimizing some code but I'm relatively new to this, so bear with me..... I'm performance testing and I'm working on a project and hit a roadblock. I tried several approaches but none seem to work... I'm working with SQL Server 2019 and trying to implement a recursive common table expression (CTE) to fetch hierarchical data from a self-referencing table. The table structure consists of an `id`, `parent_id`, and `name`. The goal is to fetch all descendants of a specific node, but I keep running into an infinite loop scenario when I execute my query. Here’s my current CTE implementation: ```sql WITH RecursiveCTE AS ( SELECT id, parent_id, name FROM my_table WHERE id = @startingNodeId -- Input parameter for the root node UNION ALL SELECT m.id, m.parent_id, m.name FROM my_table AS m INNER JOIN RecursiveCTE AS r ON m.parent_id = r.id ) SELECT * FROM RecursiveCTE; ``` The `@startingNodeId` is correctly set to the ID of the root node, but when I run this query, it just hangs indefinitely. I’ve tried adding a `MAXRECURSION` limit like this: ```sql OPTION (MAXRECURSION 100) ``` However, I still face the same scenario where the query runs indefinitely and never returns results. I validated that the data in the table is structured correctly, and there are no circular references for the nodes. I also checked the execution plan, but it doesn't seem to provide any clues as to why this is happening. Is there something I’m missing in my CTE implementation, or does anyone have suggestions on how to debug this situation effectively? My development environment is Linux. My development environment is macOS. Any help would be greatly appreciated! I'm on macOS using the latest version of Sql. I've been using Sql for about a year now. This is for a service running on Debian. Has anyone dealt with something similar? I'm working in a Ubuntu 22.04 environment. How would you solve this?