👀 Views: 70 💬 Answers: 1 📅 Created: 2025-06-14

mysql sql-joins subquery sql

I'm refactoring my project and I recently switched to I'm wondering if anyone has experience with I'm stuck on something that should probably be simple... I am working with an unexpected behavior while trying to run a query in MySQL 8.0 that involves a LEFT JOIN and a subquery. The behavior message states: `behavior 1242 (21000): Subquery returns more than 1 row`. I've checked the subquery, and it seems to be returning multiple rows as expected, but I thought using it in the LEFT JOIN would still work. Here’s the query I'm running: ```sql SELECT a.id, a.name, (SELECT b.value FROM table_b b WHERE b.a_id = a.id LIMIT 1) as first_value FROM table_a a LEFT JOIN table_b b ON a.id = b.a_id; ``` I intended to get all records from `table_a` along with one value from `table_b` per row. The scenario seems to arise from the subquery in the SELECT statement. I tried adding `LIMIT 1` to the subquery, but that's where the confusion sets in. When I include it, it works without errors, but it only returns the first row of `table_b` for every entry in `table_a`, rather than a corresponding entry based on the join condition. I’ve also considered using a Common Table Expression (CTE) to handle this, but I’d like to understand the underlying scenario with my current approach. Is there a way to structure the query correctly to avoid the subquery returning multiple rows while still effectively joining the tables? Or is there a better design pattern I should be following for this type of query? Any help would be appreciated! I'm working on a CLI tool that needs to handle this. How would you solve this? This is my first time working with Sql 3.10. My development environment is Windows 10. Has anyone else encountered this? Thanks for your help in advance! I'm on Ubuntu 20.04 using the latest version of Sql.