Question

I want to select 10 names from my table “games” for each game type.

for example: 10 rpg games, 10 action games, 10 MMO games…

The problem is that my query take up lot of resources, I am wondering if someone has the idea to write this query in a better way:

SELECT name
FROM games AS thisgame
WHERE (SELECT COUNT(1)
       FROM games
       WHERE games.game_id = thisgame.game_id 
             AND games.type > thisgame.type) <= 9

Answer 1

One way to do that fast is the variable trick. It relies on MySQL specific syntax to imitate a window function. For example, to retrieve up to two games per type:

select  s.name
,       s.type
from    (
        select  *
        ,       (@rn := if(@cur=type, @rn+1, 1)) as rn
        ,       @cur := type
        from    Games
        join    (select @cur := '') i
        order by
                type
        ) s
where   rn <= 2

Live example at SQL Fiddle.