MySQL 8.0 - advanced patterns with GROUP_CONCAT and DISTINCT in a Large Dataset
I'm not sure how to approach I'm sure I'm missing something obvious here, but I've been struggling with this for a few days now and could really use some help... I am working with an unusual scenario when using `GROUP_CONCAT` with `DISTINCT` on a large dataset in MySQL 8.0. Specifically, I am trying to retrieve a list of unique user IDs associated with orders from a table, but the results do not seem to reflect the expected uniqueness. Here’s the query I’m using: ```sql SELECT order_id, GROUP_CONCAT(DISTINCT user_id) AS unique_users FROM orders GROUP BY order_id; ``` The `orders` table contains over 1 million records, and I am noticing that the concatenated list of `user_id`s includes duplicates for some `order_id`s. I have also tried increasing the `group_concat_max_len` setting in my MySQL configuration: ```sql SET SESSION group_concat_max_len = 10000; ``` Even with this change, the results are still inconsistent. I ran the same query on a smaller dataset, and it returns the expected unique `user_id`s, which makes me think this might be related to how MySQL handles large result sets or memory. Am I missing something in the query design, or is there a potential bug in MySQL 8.0 when handling large datasets with `GROUP_CONCAT` and `DISTINCT`? Any help would be appreciated! I'm working on a web app that needs to handle this. This is part of a larger application I'm building. The stack includes Sql and several other technologies. Thanks in advance!