SELECT *
FROM comment
INNER JOIN (SELECT comment.c_id,
COUNT(*) AS cnt
FROM comment
INNER JOIN logs ON comment.c_id=logs.c_id
WHERE logs.daterate >= DATE_SUB(CURDATE(), INTERVAL 8 DAY)
AND logs.rated=1
GROUP BY comment.c_id) x ON x.c_id = comment.c_id
ORDER BY x.cnt DESC