Question

I have the following database table below

I want to display notification to the user with owner_id 1. The notification show tell the owner that two users (with ids 17 and 2) commented on his/her post with post_id 1.
I’ve tried the following query but it returns 2 rows instead. How can I can structure the query to return one row, because I want the notifications for one post to be returned together? Thank you.

SELECT DISTINCT commenters_id, id, owner_id, 
                post_id, type, UNIX_TIMESTAMP(date_done) AS date 
FROM notification 
GROUP BY commenters_id 
HAVING owner_id = '$user_id' AND commenters_id != '$user_id' 
ORDER BY date_done DESC

Answer 1

This code will not give you the commenters_id, but instead a count of how many people have replied to each post. The date will be the last time someone replied to that specific post:

SELECT
    COUNT(DISTINCT commenters_id) AS commenter_count,
    owner_id,
    post_id,
    type,
    UNIX_TIMESTAMP(MAX(date_done)) AS date 
FROM notification
WHERE owner_id = '$user_id' AND commenters_id != '$user_id' 
GROUP BY owner_id, post_id, type
ORDER BY UNIX_TIMESTAMP(MAX(date_done)) DESC