How to optimise master-slave query with count by max?

Question

I have a query to get games with current number of players for each of game ordered by the measure of what percent of player slots are filled by players.

It goes like this:

SELECT 
  g.* , COUNT( p.ID ) NUM_OF_PLAYERS 
FROM 
  games g, 
  players p
WHERE  
  g.ID = p.GAME_ID 
GROUP BY 
  g.ID 
ORDER BY 
  COUNT( p.ID ) / g.MAX_NUM_OF_PLAYERS DESC 

And it takes like 4 seconds.

And Explain gives me this mainly:

How to make it faster?

Answer 1

Try this query. Is it faster?

select g.*,p.NUM_OF_PLAYERS NUM_OF_PLAYERS 
from games g
left join 
(
select GAME_ID, COUNT( ID ) NUM_OF_PLAYERS 
  from players group by GAME_ID
) p on (g.ID = p.GAME_ID)

ORDER BY 
  p.NUM_OF_PLAYERS/g.MAX_NUM_OF_PLAYERS DESC