Найти пользователей без профиля

SELECT * FROM `auth_user` 
  WHERE not EXISTS (SELECT * FROM userprofile_userprofile WHERE userprofile_userprofile.user_id=auth_user.id );

SELECT * FROM `auth_user` 
WHERE id NOT IN (SELECT user_id FROM userprofile_userprofile)
ORDER BY `id`  ASC    

Удалить пользователей без профиля

DELETE FROM `auth_user` 
  WHERE not EXISTS (SELECT * FROM userprofile_userprofile WHERE userprofile_userprofile.user_id=auth_user.id );