Using GROUP_CONCAT on subquery in MySQL
OP almost got it right. GROUP_CONCAT should be wrapping the columns in the subquery and not the complete subquery (I’m dismissing the separator because comma is the default): SELECT i.*, (SELECT GROUP_CONCAT(userid) FROM favourites f WHERE f.itemid = i.id) AS idlist FROM items i WHERE i.id = $someid This will yield the desired result and …