Código:
INSERT INTO nuke_bbbanlist (nuke_bbbanlist)
SELECT nuke_users.user_id
FROM nuke_users LEFT JOIN nuke_bbbanlist
ON nuke_users.user_id=nuke_bbbanlist.nuke_bbbanlist
WHERE nuke_bbbanlist.nuke_bbbanlist Is Null;
Asi insertarás todos los que no esten...
Quim