SELECT COUNT(right_id) FROM `prs_rights_forum` WHERE category_id=1 AND right_id NOT IN
(SELECT right_id FROM `prs_rights_users` WHERE user_id=2)
SELECT 1 AS sort, a.author_id, a.status, u.username, u.user_colour FROM ...
В таблице `products` поле `position` для всех строк равно 0