GROUP_CONCAT with limit

Question

I have table with player-s in many-to-many relation with skill-s

The goal is to list the players and their \"top 3 skills\" with a single q

Answer 1

Here's another solution. It includes an arbitrary mechanism for resolving ties, and employes a schema slightly differing from yours...

SELECT a.player_id
     , GROUP_CONCAT(s.title ORDER BY rank) skills
  FROM
     ( SELECT x.*, COUNT(*) rank
         FROM player_skills x
         JOIN player_skills y 
           ON y.player_id = x.player_id
          AND (y.value > x.value
           OR (y.value = x.value AND y.skill_id <= x.skill_id))
        GROUP 
           BY player_id, value, skill_id
       HAVING COUNT(*) <= 3
     ) a
  JOIN skill s
    ON s.skill_id = a.skill_id
 GROUP 
    BY player_id;

http://sqlfiddle.com/#!2/34497/18

Incidentally, if you have a presentation layer/application-level code, then consider doing all the GROUP_CONCAT stuff there. It's more flexible.