Unexpected NULL values when using COALESCE in SQL Server 2019 with LEFT JOIN
I'm trying to implement I'm sure I'm missing something obvious here, but I'm working with an scenario with my SQL query in SQL Server 2019 where I am using `COALESCE` to handle potential NULL values from a LEFT JOIN... The query seems to return NULL instead of the expected default value when the related record does not exist. My query looks something like this: ```sql SELECT a.id, a.name, COALESCE(b.value, 'Default Value') AS value FROM TableA a LEFT JOIN TableB b ON a.id = b.a_id; ``` I expect that when there's no matching record in `TableB`, the `value` column should default to `'Default Value'`. However, I'm getting rows where `value` is NULL instead. I have double-checked that the join condition is correct, and I even tried using different default values, but the results remain the same. To troubleshoot, I ran the following query to check the data: ```sql SELECT a.id, b.value FROM TableA a LEFT JOIN TableB b ON a.id = b.a_id; ``` This returned several rows where `b.value` was indeed NULL, but I still don't understand why `COALESCE` isn’t providing the default value. I also verified that there are no triggers or constraints that could be affecting this behavior. Is there a specific detail I might be missing when using `COALESCE` in conjunction with a LEFT JOIN? Any insights or suggestions would be greatly appreciated! Has anyone else encountered this? This is happening in both development and production on Ubuntu 20.04. What are your experiences with this?