Dělení for do kategorií.

            return $this->database->query('SELECT  *
                                            FROM    (
                                                SELECT  DISTINCT
                                                    c.forum_category_title AS c_forum_category_title,
                                                    c.forum_category_description AS c_forum_category_description,
                                                    f.forum_title AS f_forum_title
                   
                                                FROM    forum_category c
                                                LEFT JOIN
                                                    forum f
                                                ON      c.forum_category_id = f.forum_cat_id

                                                GROUP BY
                                                    c.forum_category_title, f.forum_title WITH ROLLUP
                                                HAVING  c_forum_category_title IS NOT NULL
                                            ) q
                                            ORDER BY
                                                c_forum_category_title, f_forum_title')->fetchAll();