MySQL 8.0: Unexpected NULL results from COALESCE when using GROUP BY with JSON columns
I'm a bit lost with I'm working with an scenario with MySQL 8.0 where using the `COALESCE` function in conjunction with `GROUP BY` on a JSON column is returning unexpected NULL values. I'm trying to aggregate data and substitute NULLs with default values, but it seems that when I group by a JSON attribute, the `COALESCE` does not behave as expected. Here's the query I'm using: ```sql SELECT id, COALESCE(JSON_UNQUOTE(JSON_EXTRACT(data, '$.name')), 'Unknown') AS name, COUNT(*) AS item_count FROM my_table GROUP BY JSON_UNQUOTE(JSON_EXTRACT(data, '$.name')); ``` In this case, I expect the `name` value to be returned as 'Unknown' when the `$.name` key does not exist or is NULL. However, I'm getting NULL in the results instead of 'Unknown'. I’ve tried validating the JSON structure and ensured that `data` is indeed a valid JSON column. Additionally, I checked that the column is indexed, yet the performance seems fine, and I don't notice any errors in execution. I also attempted to wrap the `JSON_EXTRACT` in another `COALESCE`, like this: ```sql SELECT id, COALESCE(COALESCE(JSON_UNQUOTE(JSON_EXTRACT(data, '$.name')), 'Unknown'), 'Unknown') AS name, COUNT(*) AS item_count FROM my_table GROUP BY JSON_UNQUOTE(JSON_EXTRACT(data, '$.name')); ``` But this still resulted in NULL when there were no corresponding JSON keys. Any insights on why this might be happening or how to work around this scenario? Is there a better way to handle JSON aggregation in MySQL 8.0? Thanks in advance for any help! I'd be grateful for any help.