MySQL-query om de meest vergelijkbare numerieke rij te vinden

In een kleine verfijning van de methode van @eggyal heb ik het aantal items opgenomen waarmee we kunnen matchen.

SELECT   u2.user_id

-- join our user to their scores
FROM     (users u1 JOIN scores s1 USING (user_id))

-- and then join other users and their scores
    JOIN (users u2 JOIN scores s2 USING (user_id))
      ON s1.item_id  = s2.item_id
     AND u1.user_id != u2.user_id

-- filter for our user of interest
WHERE    u1.user_id = ?

-- group other users' scores together
GROUP BY u2.user_id

-- subtract the degree of difference in correlating scores from the number of correlating scores
ORDER BY (SUM(s1.item_id = s2.item_id) - 
  ( SUM(ABS(s2.score - s1.score) + ABS(u2.self - u1.self) ) ) ) DESC