MySQL JOIN query returns empty result set when using multiple LEFT JOINs on large datasets
I'm experimenting with I'm testing a new approach and I'm integrating two systems and I've been banging my head against this for hours... I'm working with a MySQL 8.0 database and trying to retrieve data from three related tables using LEFT JOINs. However, despite having matching data in the tables, my query is returning an empty result set. Here’s the query I wrote: ```sql SELECT a.id, a.name, b.description, c.value FROM table_a a LEFT JOIN table_b b ON a.id = b.a_id LEFT JOIN table_c c ON b.id = c.b_id; ``` I verified that `table_a` contains records that should match with `table_b` and `table_c`. I checked for null values in the join columns; both `b.a_id` and `c.b_id` have valid matches in their respective tables. To debug, I ran segments of the query separately: ```sql SELECT * FROM table_a; SELECT * FROM table_b; SELECT * FROM table_c; ``` All these queries return results as expected. I even tested simpler JOINs by omitting one of the LEFT JOINs, and it worked fine, returning the expected results. When I run the query with just one LEFT JOIN instead of two, it yields results. I also checked the database engine and confirmed that all tables are using InnoDB. The `b.a_id` and `c.b_id` are both indexed, which I thought would help performance. However, I’m still at a loss as to why the full query returns an empty result. Has anyone encountered a similar scenario with JOINs in MySQL? I would greatly appreciate any insights or troubleshooting steps I might have missed. I'm working on a API that needs to handle this. Am I missing something obvious? Is there a simpler solution I'm overlooking? Could this be a known issue?