Я так понял тут
$dq = mysql_query("SELECT SQL_CALC_FOUND_ROWS
`u`.`id` AS `user_id`,
`u`.`name` AS `user_name`,
(SELECT COUNT(*) FROM `questions` AS `q` WHERE `q`.`user_addressee_id`=`u`.`id` AND `q`.`answer`!='') AS `count_questions`
FROM `users` AS `u