Get User Rank Based on Sum with Pagination - mysql

Question

There are several rank posts out there but I have yet to see one dealing with when the results are paginated and when the ranking criteria (in this case: points) is equal to the previous user. I have tried a few of the pre-existing examples but none have worked.
I have a table called "users" with the column "id". I also have a table called "points" with the columns "user_id" and "amount".
I need:
1.) Users with duplicate sum of points to have the same rank
Points Table
user_id amount
1 10
2 20
1 5
3 20
3 -5
4 5
Rank should be
rank user_id total
1 2 20
2 1 15
2 3 15
3 4 5
2.) Needs to maintain the ranking from one page to another so the rank has to be gathered in the query and not the resulting PHP.
3.) Display ALL users not just ones with rows in the points table because some users have 0 points and I want to display them last.
Right now I'm just listing the users in order of their points but their rank is not gathered because it wasn't working.
$getfanspoints = mysql_query("SELECT DISTINCT id,
(SELECT SUM(amount) AS points FROM points WHERE points.user_id = users.id) AS points
FROM users
ORDER BY points DESC LIMIT $offset, $fans_limit", $conn);
I've read these solutions and none have worked.
[Roland's Blog][1]
[How to get rank based on SUM's][2]
[MySQL, get users rank][3]
[How to get rank using mysql query][4]
and a few others whose link I can't find right now.
Any suggestions?
[EDIT]
I used ypercube's bottom answer.

Answer 1

SELECT COUNT(*) AS rank
, t.user_id
, t.total
FROM
( SELECT user_id
, SUM(amount) AS total
FROM points
GROUP BY user_id
) AS t
JOIN
( SELECT DISTINCT
SUM(amount) AS total
FROM points
GROUP BY user_id
) AS dt
ON
t.total <= dt.total
GROUP BY t.user_id
ORDER BY rank
, user_id
But the above may be really slow with a big table and points awarded often. It might be really better to have just this and calculate the ranks in your application code:
SELECT users.id AS user_id
, SUM(amount) AS total
FROM
users
LEFT JOIN
points
ON points.user_id = users.id
GROUP BY users.id
ORDER BY total DESC
, user_id
This will work, too (edited, to work with the users table and with OFFSET):
SELECT *
FROM
( SELECT
#rank := #rank + (#t <> total) AS rank
, user_id
, #t := total AS total
FROM
( SELECT users.id AS user_id
, COALESCE(SUM(amount),0) AS total
FROM users
LEFT JOIN points
ON users.id = points.user_id
GROUP BY users.id
) AS o
CROSS JOIN
( SELECT #rank := 0, #t := -999999
) AS dummy
ORDER BY total DESC
, user_id
) tmp
LIMIT x OFFSET y