SELECT `c`.*, `users`.`login`, `users`.`logo` AS `user_ava`, `users`.`sex` AS `sex`, `users`.`balance` AS `balance`, `comments`.`text` AS `textcomm`
FROM `otvety` AS `c`
LEFT JOIN `comments` ON `comments`.`otv_id` = `c`.`id`
LEFT JOIN `users` ON `users`.`id` = `c`.`user_id`
WHERE `c`.`post_id`='$id'
GROUP BY `c`.`id`
ORDER BY `c`.`date` ASC