MySQL 5.7: Inconsistent Results with LEFT JOIN and WHERE Clauses in Nested Queries
I've looked through the documentation and I'm still confused about I'm converting an old project and I'm stuck on something that should probably be simple... I've been struggling with this for a few days now and could really use some help... I'm experiencing inconsistent results when using a LEFT JOIN along with a WHERE clause in a nested query in MySQL 5.7. The outer query seems to exclude some rows I expect to see, and I'm not sure why. Here's the query I'm running: ```sql SELECT a.id, a.name, b.value FROM table_a a LEFT JOIN ( SELECT id, value FROM table_b WHERE status = 'active' ) b ON a.id = b.id WHERE a.category = 'electronics'; ``` The scenario arises because I expect all entries from `table_a` with the category 'electronics' to be returned, even if they don't have a corresponding active entry in `table_b`. However, it seems like some rows are being filtered out when they shouldn't be. I've tried removing the WHERE clause from the subquery, but that still doesn't resolve the scenario. Additionally, I checked the data and confirmed that there are entries in `table_a` that meet the category condition but are not showing up in the results. To debug, I executed the subquery independently and verified that it returns the expected rows. When I run the query, I see that rows from `table_a` where there are missing matches in `table_b` return `NULL` for `b.value`, but they don’t appear in the final result set as expected. I'm worried that I'm misusing the JOIN or WHERE clauses. What’s causing this behavior, and how can I adjust my query to get the complete expected result set? I also tried using an outer query without additional filtering and got the same results. Any insights would be appreciated! I'm working on a application that needs to handle this. Has anyone else encountered this? My development environment is Ubuntu. I'm using Sql 3.11 in this project. Could this be a known issue?