我剛剛把 $sql = "SELECT f.*, p.post_time, p.post_username, u.username, u.user_id FROM " . FORUMS_TABLE . " f, " . POSTS_TABLE . " p, " . USERS_TABLE . " u WHERE p.post_id = f.forum_last_post_id AND u.user_id = p.poster_id UNION ( SELECT f.*, NULL, NULL, NULL, NULL FROM...