Getting row position in a temporary table MySQL

Question

So I'm in the process of writing a temporary table that sets position according to total_points in a DESC order, IE the more points a user has, the higher rank they will have.

I will also be selecting a subscriber_id out of this table to get a given users current position

However, I'm running into a lot of strange problems, here is my code:

SET @rownum := 0;

SELECT t.`subscriber_id`,
t.`total_points`,
s.`account_type`,
@rownum := @rownum + 1 AS `position`
FROM `subscribers_points` t
LEFT JOIN (
    SELECT `id`, `account_type` 
    FROM `subscribers`
) s
    on s.`id` = t.`subscriber_id`
WHERE t.`year` = 2015
AND t.`month` = 1
ORDER BY t.`total_points` DESC

I want to filter out all account_types of 1,2, and 9, but anytime I add it to the subscribers_points WHERE clause my table no longer gives position base on total_points , but by subscriber_id which is just weird and doesn't make sense to me.

For clarification, the table subscribers contains the account_type field. The subscriber_points table contains the total_points field.

This is how an ideal table should look:

-------------------------------------------------------------
|  subscriber_id |  position |  total_points | account_type  |
-------------------------------------------------------------
|    52          |     1     |       10      |       7       |
|   125          |     2     |       8       |       4       |
|    87          |     3     |       9       |       3       |
|    12          |     4     |       5       |       6       |
|    45          |     5     |       2       |       4       |
-------------------------------------------------------------

Thank you in advance

Answer 1

MySQL is wonky for calculating inter-row values:

Basic simple table with 6 sequential values:

mysql> create table foo (x int);
mysql> insert into foo (x) values (0), (1), (2), (3), (4), (5);

mysql> set @pos := 0;
mysql> select @pos := @pos + 1, x from foo where x not in (2, 3);
+------------------+------+
| @pos := @pos + 1 | x    |
+------------------+------+
|                1 |    0 |
|                2 |    1 |
|                3 |    4 |
|                4 |    5 |
+------------------+------+

Everything looks OK. We've eliminated two rows, the position number is sequential, and it looks like MySQL properly doesn't evaluate the @pos update unless a row is included in the result set. But then you add some ordering into the system:

mysql> set @pos := 0;
mysql> select @pos := @pos + 1, x from foo where x not in (2, 3) order by x desc;
+------------------+------+
| @pos := @pos + 1 | x    |
+------------------+------+
|                1 |    5 |
|                2 |    4 |
|                3 |    1 |
|                4 |    0 |
+------------------+------+

Note how the position is STILL incrementing, even though we've reversed the ordering of the rows. You'd think the @pos + 1 stuff would be evaluated as the table is scanned and rows are included/excluded. But nope. It's somehow done AFTER the rows are included and sorted.

This means that your calculated position is basically independent of the values you're retrieving in the rest of the query. But even more confusing, if you sort by the position:

mysql> set @pos := 0;
mysql> select @pos := @pos + 1 as pos, x from foo where x not in (2, 3) order by pos desc;
+------+------+
| pos  | x    |
+------+------+
|    4 |    5 |
|    3 |    4 |
|    2 |    1 |
|    1 |    0 |
+------+------+

the x values are sorted along with the position. So whatever is gluing together those position values with the matched records is... wonky.

Answer 2

OK I found the solution, but it basically consisted of creating 2 Temporary tables to get the exact values I want in the same place THEN running a SELECT for the proper rank given to a user.

Code Below:

    CREATE TEMPORARY TABLE IF NOT EXISTS `temp_rank_table` AS(
        SELECT p.`subscriber_id`, p.`total_points`, s.`account_type`
        FROM `subscribers_points` p 
            LEFT JOIN `subscribers` s
            ON s.`id` = p.`subscriber_id`
        WHERE p.`year` = _year
        AND p.`month` = _month
        AND s.`account_type` BETWEEN 3 AND 8
        AND `password_created` = 1
        AND `verified` = 1
        AND `active` = 1
        ORDER BY p.`total_points` DESC
    );

    SET @rank=0;

    CREATE TEMPORARY TABLE IF NOT EXISTS `temp_rank_table_count` AS(
        SELECT @rank:=@rank+1 AS `rank`, `subscriber_id`, `total_points`
        FROM `temp_rank_table`
        ORDER BY `total_points` DESC
    );

    #

    SELECT t.`rank`, t.`subscriber_id`, t.`total_points`
    FROM `temp_rank_table_count` t
    WHERE `subscriber_id` = _subscriber_id;

    DROP TABLE `temp_rank_table`;
    DROP TABLE `temp_rank_table_count`;