DECLARE
    FUNCTION f1 (vid studenci.id_student%TYPE) RETURN BOOLEAN IS
        vx CHAR(1) ;
        BEGIN
            SELECT DISTINCT 'x' INTO vx FROM egzaminy e
                WHERE e.id_student = vid ;
            RETURN TRUE ;
        EXCEPTION
            WHEN NO_DATA_FOUND THEN RETURN FALSE ;
    END f1;
BEGIN
    FOR vc1 IN (SELECT id_student, nazwisko, imie
                FROM studenci
                ) LOOP
        IF NOT f1(vc1.id_student) THEN
                DBMS_OUTPUT.put_line(vc1.id_student) ;
        END IF;
    END LOOP ;
END ;