Something

SELECT post.id
     FROM list_posts AS post
     LEFT OUTER JOIN private ON (post.id = private.pid)
     LEFT OUTER JOIN official_user AS adminu
     LEFT OUTER JOIN count_comments AS ccount ON (post.id = ccount.pid)
     WHERE
         ( post.id = '5' ) AND 
         (
           ( post.private = false )
        OR
           (
             (adminu.user = 'good')
         AND
             (private.uid = adminu.user)
           )
         )
LIMIT 1