Calculate Rank with points - php

Question

I have a database with users and points (in fact it's a percentage, but that doesn't matter). The user(s) with the highest number of points is on the first rank, the second on the second rank ...
I could get the rank of a $searchedUserID if I did somethink like this:
SELECT `user_id`, `points` FROM `usertable` ORDER BY `points` DESC
/** This function returns the rank of a user. The rank nr. 1 is the best.
* It is possible that some users share a rank.
*
* #param int $searchedUserID the ID of the user whose rank you would like to
* know
*
* #return int rank
*/
function getUserRank($searchedUserID)
{
$userArray = getAllUsersOrderedByPoints();
$rank = 0;
$lastPoints = -1; // Never happens
foreach ( $userArray as $user) {
if ($user['point'] != $lastPoints) $rank++;
if ($user['user_id'] == $searchedUserID) break;
}
return $rank;
}
Isn't there a more direct way to get this with (My)SQL?
If not: Can the PHP-part be improved?
(edit: I could store the rank calculated by PHP directly in the database ... but this would mean I had to make quite a lot of UPDATEs.)
edit2: Perhaps GROUP BY could be used? Something like:
SELECT `user_id`, `points` FROM `usertable` GROUP BY `points` ORDER BY `points` DESC
The problem with this query is the possibility, that I don't get the searched user_id. It would be necessary to send a second query:
SELECT `user_id` FROM `usertable` WHERE `points` = $pointsOfTheUser

Answer 1

You ask:
Isn't there a more direct way to get this with (My)SQL?
Yes. In SQL:2003, you could use the DENSE_RANK() window function. In MySQL, you can simulate this, as the (dense) rank of a record by some score is simply the count + 1 of distinct better scores:
SELECT u.user_id,
u.points,
1 + COUNT(DISTINCT others.points) AS `dense_rank`
FROM users u
LEFT JOIN users others
ON u.points < others.points -- Which other users have more points?
WHERE user_id = ?
GROUP BY 1, 2;

Answer 2

perhaps an inner join with group by and sort would do the trick?
SELECT * FROM
INNER JOIN
(
SELECT user_id AS uid, max(points) AS score
FROM usertable GROUP BY user_id
)
AS ds ON usertable.user_id = ds.uid AND usertable.points = ds.score
ORDER BY score DESC
Just thinking on paper (pixels) .. wouldn't that give you the list in order from highest points to lowest with a unique record per user ... or are you looking to have these sorted where you can clarify a tie as a single "place" in the rankings?