WTA Query For Winner Drawing

Dear List,
I'm developing a winner drawing application using PHP+MySQL. As we know =
that MySQL has a built in function RAND() to randomize the result. But =
using that function will only randomize, my goal is the player with =
higher point gets higher posibility when randomizing. Anybody can help? =
Many thanks.



sangprabv
sangprabv@gmail.com
http://www.petitiononline.com/froyo/



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Re: WTA Query For Winner Drawing

On 7/9/2010 3:04 AM, sangprabv wrote:
> Dear List,
> I'm developing a winner drawing application using PHP+MySQL. As we know that MySQL has a built in function RAND() to randomize the result. But using that function will only randomize, my goal is the player with higher point gets higher posibility when randomizing. Anybody can help? Many thanks.
>

Here's an idea...

Perform N queries into your table and collect the PK values for all rows
where score > rand() (adjust appropriately for the range of scores). N
should be an appropriately large number relative to the number of
entries you are trying to randomize. N should be at least 1/2 of the
total number of rows. For smaller starting sets, the value of N could
even be several multiples of your starting set. The more you collect,
the more smoothly you will randomize and the more accurate the weights
will be.

That way, each potential winner (the higher the score the better) will
appear at most N times in the "drawing" table. Those original rows whose
scores were never above the rand() threshold may not even appear in the
drawing table.

From that weighted table, you can make another random selection for the
actual winner.

--
Shawn Green
MySQL Principle Technical Support Engineer
Oracle USA, Inc.
Office: Blountville, TN

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