MySQL 5.7: Problems with NULL values in JSON_OBJECT when using GROUP BY
I'm working on a project and hit a roadblock. I've spent hours debugging this and I'm deploying to production and Quick question that's been bugging me - I'm working on a personal project and I'm working with an scenario when trying to aggregate data into a JSON object using `JSON_OBJECT` in MySQL 5.7..... The query is supposed to group results by `category_id`, but I am getting unexpected NULL values in the JSON output when certain categories have no corresponding rows. Here's the query I'm using: ```sql SELECT category_id, JSON_OBJECT('items', GROUP_CONCAT(item_name)) AS items FROM items_table GROUP BY category_id; ``` When `category_id` has no items associated with it, the output for that category shows as `NULL` instead of an empty JSON object `{}`. However, I want it to return an empty JSON object instead of NULL, so that I maintain a consistent response format. I tried wrapping the `JSON_OBJECT` call with `COALESCE`, like this: ```sql SELECT category_id, COALESCE(JSON_OBJECT('items', GROUP_CONCAT(item_name)), '{}') AS items FROM items_table GROUP BY category_id; ``` But the output is still `NULL` for categories with no items. I've also considered using a LEFT JOIN from a categories table to ensure every category is returned, but I'm not quite sure how to implement that effectively without complicating the query too much. Can anyone provide a solution to this question or suggest an alternative approach to ensure I get an empty JSON object for categories without items? My development environment is Ubuntu. How would you solve this? This is part of a larger application I'm building. Am I missing something obvious? Any suggestions would be helpful. I'm developing on Linux with Sql. I'd love to hear your thoughts on this. Am I approaching this the right way?