MySQL 8.0 - implementing JSON_AGG() when Aggregating Nested JSON Objects
I'm working with an scenario while trying to use the `JSON_AGG()` function in MySQL 8.0. I have a table `orders` that stores orders along with their associated items, and I want to group the results to create a JSON representation of each order with its items nested. However, the output is missing some of the items, and I'm not sure why. Here's the snippet of my current query: ```sql SELECT o.order_id, JSON_AGG(i) AS items FROM orders o JOIN items i ON o.order_id = i.order_id GROUP BY o.order_id; ``` When I run this query, I expect to see a JSON array for each `order_id` with all associated items included. However, in some cases, the `items` array is incomplete, as if JSON_AGG is not aggregating all the rows correctly. I checked for duplicate `order_id`s in the `items` table, but everything seems fine. I've also tried using `DISTINCT` within the `JSON_AGG()` function: ```sql SELECT o.order_id, JSON_AGG(DISTINCT i) AS items FROM orders o JOIN items i ON o.order_id = i.order_id GROUP BY o.order_id; ``` This didn't resolve the scenario either; it still results in missing items in the JSON output. To troubleshoot, I ran the JOIN separately to see if the data was coming through correctly: ```sql SELECT o.order_id, i.item_id FROM orders o JOIN items i ON o.order_id = i.order_id; ``` The JOIN returns all the expected rows, so the data exists, but something seems to go wrong during the aggregation. Is there a specific limitation or condition I need to be aware of when using `JSON_AGG()` in this way? Any insights on how to ensure all items are included would be greatly appreciated.