Question

I’m looking for a way to select the most occurring value, e.g. the person who posted most for each thread;

SELECT MOST_OCCURRING(user_id) FROM thread_posts GROUP BY thread_id

Is there a good way to do this?

Answer 1

If you want a count on a per thread basis, I think you can use a nested query; grouping by thread first and then by user:

SELECT thread_id AS tid,
    (SELECT user_id FROM thread_posts 
        WHERE thread_id = tid 
        GROUP BY user_id
        ORDER BY COUNT(*) DESC
        LIMIT 0,1) AS topUser
FROM thread_posts
GROUP BY thread_id