DELETE FROM k_rent_books
   WHERE reader_id not in(select reader_id
   from k_reader where months_between(sysdate,valid_until) > 120);

SELECT * INTO pom FROM k_reader
	where months_between(sysdate,valid_until) > 120);

DELETE FROM k_reader
	where months_between(sysdate,valid_until) > 120);

DELETE FROM k_person
    where person_id in (select person_id from pom);