Hello, I have this strange problem that the following statement works: phpbb=> select user_id, username from phpbb_users phpbb-> where user_id in (select ban_userid from phpbb_banlist); user_id | username ---------+---------- 3 | La-Li (1 row) But the negative one returns nothing: phpbb=> select user_id, username from phpbb_users phpbb-> where user_id not in (select ban_userid from phpbb_banlist); user_id | username ---------+---------- (0 rows) Eventhough there are 3 other users in the phpbb_users table: phpbb=> select user_id, username from phpbb_users; user_id | username ---------+----------- -1 | Anonymous 3 | La-Li 4 | Vasja 2 | Alex (4 rows) And there is only one user (La-Li, id=3) in the phpbb_banlist: phpbb=> select * from phpbb_banlist; ban_id | ban_userid | ban_ip | ban_email --------+------------+--------+------------- 1 | 3 | | 4 | | | *@gmail.com (2 rows) Thank you Alex