-- Below I get an extra column that auto increments for each row.

SELECT @i:=0;
SELECT p.*, @i:=@i+1 AS rank
FROM photos p
WHERE (p.created_at >= '2010-11-01')
ORDER BY p.id DESC

-- I get something like this:
/*
+-----+-------+------+
| id  | title | rank |
| 300 | bla 3 | 1    |
| 299 | bla 2 | 2    |
| 298 | bla 1 | 3    |
+-----+-------+------+
*/

-- But if I try to do some aggregation such as below:

SELECT @i:=0;
SELECT p.*, COUNT(v.photo_id) AS votes, @i:=@i+1 AS rank
FROM photos p
LEFT OUTER JOIN v on (p.id = v.photo_id)
WHERE (p.created_at >= '2010-11-01')
GROUP BY p.id
ORDER BY votes DESC

-- The auto incrementing column becomes corrupt it doesn't make any sense