I'm trying to get a list of partners (roleid = 511) who posted comments in the month of April of this year.
I would like to embed the count(*) of comments in each row.
And I would like to sort the results by the partner having the most comments first and decend to the partner with the least comments (but > 0) at the bottom of the list.

Here's what I've come up with (which is not working):
Code MySQL:
SELECT u.uid, u.name, u.mail (SELECT @comment_count:=count(*) FROM comments c WHERE c.uid = u.uid AND EXTRACT(YEAR_MONTH FROM c.timestamp) = '201204') AS april comments, DATE_FORMAT(FROM_UNIXTIME(u.access),'%b-%d-%Y') AS 'last visit'
  FROM users AS u
    INNER
      JOIN users_roles AS ur
        ON ur.uid = u.uid
      AND ur.rid = 511
  WHERE u.mail NOT LIKE '%example.com%' AND EXTRACT(YEAR_MONTH FROM u.access) > '201204' ORDER BY @comment_count;
 
 
mysql> describe users;
+------------------+------------------+------+-----+---------+----------------+
| Field            | Type             | Null | Key | Default | Extra          |
+------------------+------------------+------+-----+---------+----------------+
| uid              | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
| name             | varchar(60)      | NO   | UNI |         |                |
| pass             | varchar(32)      | NO   |     |         |                |
| mail             | varchar(64)      | YES  | MUL |         |                |
| mode             | tinyint(1)       | NO   |     | 0       |                |
| sort             | tinyint(1)       | YES  |     | 0       |                |
| threshold        | tinyint(1)       | YES  |     | 0       |                |
| theme            | varchar(255)     | NO   |     |         |                |
| signature        | varchar(255)     | NO   |     |         |                |
| created          | int(11)          | NO   | MUL | 0       |                |
| access           | int(11)          | NO   | MUL | 0       |                |
| status           | tinyint(4)       | NO   | MUL | 0       |                |
| timezone         | varchar(8)       | YES  |     | NULL    |                |
| language         | varchar(12)      | NO   |     |         |                |
| picture          | varchar(255)     | NO   |     |         |                |
| init             | varchar(64)      | YES  |     |         |                |
| data             | longtext         | YES  |     | NULL    |                |
| login            | int(11)          | NO   |     | 0       |                |
| timezone_name    | varchar(50)      | NO   |     |         |                |
| signature_format | smallint(6)      | NO   |     | 0       |                |
+------------------+------------------+------+-----+---------+----------------+
20 rows in set (0.00 sec)
 
mysql> describe comments;
+-----------+---------------------+------+-----+---------+----------------+
| Field     | Type                | Null | Key | Default | Extra          |
+-----------+---------------------+------+-----+---------+----------------+
| cid       | int(10)             | NO   | PRI | NULL    | auto_increment |
| pid       | int(10)             | NO   | MUL | 0       |                |
| nid       | int(10)             | NO   | MUL | 0       |                |
| uid       | int(10)             | NO   | MUL | 0       |                |
| subject   | varchar(64)         | NO   |     |         |                |
| comment   | longtext            | NO   |     | NULL    |                |
| hostname  | varchar(128)        | NO   |     |         |                |
| timestamp | int(11)             | NO   |     | 0       |                |
| status    | tinyint(3) unsigned | NO   | MUL | 0       |                |
| format    | smallint(6)         | NO   |     | 0       |                |
| thread    | varchar(255)        | NO   |     |         |                |
| name      | varchar(60)         | YES  |     | NULL    |                |
| mail      | varchar(64)         | YES  |     | NULL    |                |
| homepage  | varchar(255)        | YES  |     | NULL    |                |
+-----------+---------------------+------+-----+---------+----------------+
14 rows in set (0.00 sec)
 
mysql> describe role;
+-------+------------------+------+-----+---------+----------------+
| Field | Type             | Null | Key | Default | Extra          |
+-------+------------------+------+-----+---------+----------------+
| rid   | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
| name  | varchar(64)      | NO   | UNI |         |                |
+-------+------------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)