Count the "ratio?" for wins and losses

I've already got this to work but it's a really bad approach and i need some help with factorization of my query.

SELECT `GameDate`,
   COUNT(CASE
           WHEN `P1Outcome`= 'win' AND  P2Param = 'a' THEN 1 
         END) AS a_win,
   COUNT(CASE
           WHEN `P1Outcome`= 'loss' AND  P2Param = 'a' THEN 1 
         END) AS a_loss,
   COUNT(CASE
           WHEN `P1Outcome`= 'win' AND  P2Param = 'b' THEN 1
         END) AS b_win,
   COUNT(CASE
           WHEN `P1Outcome`= 'loss' AND  P2Param = 'b' THEN 1
         END) AS b_loss
    FROM games 
    WHERE `P2Param` IN ( 'a', 'b', 'c' ) 
    GROUP BY GameDate

This will get me an query that i can use in my php application but i would like to skip having to make the actual ratio calculation in php and fetch it directly with SQL.

So basically what i've been trying to do is something similar to this:

   COUNT(CASE
           WHEN `P1Outcome`= 'win' AND  P2Param = 'a' THEN 1 Else -1
         END) AS a_ratio,

But just as the beginer i'm, i can't figure it out how i can make this to work.

EDIT: Sorry for not explaining my regards in more details, here is the thing. I'm creating an statistics component and i need to fetch the ratio for a period of time in order to display it as an graph. So the following things are required:

GameDate (1,2,3,4... days ago) The ratio for the player based on to different params (maps in this case)

So in short this is what i got at the moment:

GameDate      a_win      a_loss    b_win      b_loss 
2011/04/25     x          x         x           x
2011/04/23     x          x         x           x
....

So everything works out great, but i would like to have the actual ratio calculation made in SQL because at the moment i need to make it in php e.g $ratio = $q[a_win]-$q[a_loss] and due to the fact that I've a lot of different param my query is like double the size because i need to fetch both the win and loss instead of just the ratio like i want in the first place.

SELECT `GameDate`,
   SUM(CASE `P2Param`
         WHEN 'a' THEN CASE P1Outcome WHEN 'win' THEN 1 ELSE -1 END
         ELSE 0
       END) AS a_ratio,
   SUM(CASE `P2Param`
         WHEN 'b' THEN CASE P1Outcome WHEN 'win' THEN 1 ELSE -1 END
         ELSE 0
       END) AS b_ratio
FROM games
WHERE `P2Param` IN ( 'a', 'b', 'c' ) 
GROUP BY GameDate

What is very important COUNT just returns number of rows regardless of what you count unless you use COUNT(DISTINCT ...) which in turn returns count of distinct values. To sum up some values which you produce for every row use SUM(...). Make sure what happens in your DBMS when an expression in the SUM() function evaluates to NULL - some databases will just make the whole SUM return NULL.

To get ratio of any kind of data you can do:

select _date_, (SUM(case when _your_test_ then 1 else 0 end) / count(1)) as ratio
from _yout_table_
group by _date_

And if you just want to calculate a sum of some values:

select _date_, SUM(case when _your_test_ then 1 else 0 end) as number_of_something
from _yout_table_
group by _date_

What about:

  SELECT COUNT(id), P1Outcome, P2Param
    FROM games
GROUP BY P2Param, P1Outcome

It will returns you a resultset with 3 columns:

• counted values for param and outcome
• outcome
• param

With that you can do more in my opinion.

SELECT GameDate, P2Param, SUM(CASE WHEN P1Outcome = 'win' THEN 1 ELSE -1 END) AS ratio
    FROM games
    GROUP BY GameDate, P2Param