👀 Views: 6802 💬 Answers: 1 📅 Created: 2025-07-14

mysql sql cte

I've spent hours debugging this and I'm trying to implement I need help solving I'm trying to configure I'm working with MySQL 8.0 and trying to fetch hierarchical data using a Common Table Expression (CTE). The goal is to retrieve all descendants of a given node in a parent-child relationship. However, I'm working with unexpected results where some nodes appear multiple times in the output, even though they should only be listed once. I've structured my CTE as follows: ```sql WITH RECURSIVE hierarchy AS ( SELECT id, parent_id, name FROM categories WHERE id = ? -- ID of the parent node to start from UNION ALL SELECT c.id, c.parent_id, c.name FROM categories c JOIN hierarchy h ON c.parent_id = h.id ) SELECT * FROM hierarchy; ``` I've tested it with various parent IDs, but I've noticed that some child nodes that should only be linked to one parent show up with multiple parent IDs in the result set. I've also checked for duplicate entries in the `categories` table, but everything seems fine. Additionally, I've experimented with adding a `DISTINCT` clause to the final select, but that doesn't seem to resolve the scenario either. What could be causing this unexpected duplication in the results? Is there a better way to implement this recursive query to ensure that each node is only returned once? For context: I'm using Sql on Ubuntu 22.04. I'd love to hear your thoughts on this. My team is using Sql for this desktop app. I've been using Sql for about a year now. What are your experiences with this?