SELECT t.id,
  t.forum_id,
  t.name AS topic_title,
  t.displays AS displays_count,
  t.replies AS replies_count,
  t.author_id AS topic_author_id,
  t.author_name AS topic_author_name2,
  t.last_post AS last_post_id,
  p.id,
  p.author_id AS last_post_author_id,
  p.author_name AS last_post_author_name2,
  p.timestamp AS last_post_timestamp,
  u.id,
  u.login AS last_post_author_name,
  u2.id,
  u2.login AS topic_author_name
FROM `topic`
AS t,
  `post` AS p,
  `user` AS u,
  `user` AS u2
WHERE ( t.forum_id = 1 AND p.id = t.last_post ) AND # i tutaj zaczynają się schody gdyż:
  #    jeśli p.author_id <> 0 wtedy musi być spełniony ten warunek u.id = p.author_id
  #    a jeśli p.author_id = 0 whtedy ten p.author_name <> ""
AND
  #    jeśli t.author_id <> 0 wtedy musi być spełniony ten warunek u2.id = t.author_id
  #    a jeśli t.author_id = 0 wtedy musi być spełniony ten warunek t.author_name <> ""
ORDER BY p.timestamp ASC;