CREATE TRIGGER insert_into_view
    instead OF INSERT ON three_tables
    FOR each ROW
    DECLARE
    clients_id int;
    private_pesel int;
    private_address VARCHAR2(50);
    BEGIN
        SELECT id INTO clients_id FROM client WHERE name=:NEW.name AND surname=:NEW.surname AND ROWNUM=1;
        SELECT pesel INTO private_pesel FROM client_private;
        SELECT address INTO private_address FROM client_private;
        IF private_pesel=:NEW.pesel AND private_address=:NEW.address THEN
            DBMS_OUTPUT.put_line('DANE PRYWATNE ISTNIEJĄ JUŻ W BAZIE DANYCH');
        ELSE
            INSERT INTO client_private(id,pesel,address) VALUES(clients_id, :NEW.pesel, :NEW.address);
        END IF;
        INSERT INTO shopping(id, client_id, number_of_products, total_price) VALUES(clients_id, clients_id, :NEW.number_of_products, :NEW.total_price);
        EXCEPTION
            WHEN NO_DATA_FOUND THEN DBMS_OUTPUT.put_line('NIE MA TAKIEGO UŻYTKOWNIKA');
        END;