MySQL update statement to store ranking positions

In MySQL, you can use row_number.

Here's an example of using it in a SELECT:

select @rownum:=@rownum+1 ‘rank’, p.* 
from player p, (SELECT @rownum:=0) r 
order by score desc;

If you INSERT INTO using a SELECT like this, you will get your rankings.

Here's a way to do it:

SET @r=0;
UPDATE table SET Ranking= @r:= (@r+1) ORDER BY Score DESC;

/* use this if you just want to pull it from the db, but don't update anything */
SET @r=0;
SELECT *, @r:= (@r+1) as Ranking FROM table ORDER BY Score DESC;