Oracle 21c

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CREATE TABLE Kupac (
    kupac_PIB INT PRIMARY KEY,
    naziv_firme_kupac VARCHAR2(255)
);
CREATE TABLE Kontakt (
    id_kontakt INT GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
    mail VARCHAR2(100),  
    telefon VARCHAR2(100),
    kupac_PIB INT, 
    partner_PIB INT, 
    naziv_firme_kupac VARCHAR2(255),
    naziv_poslovni_partner VARCHAR2(255),
    CONSTRAINT kontakt_kupac
        FOREIGN KEY(kupac_PIB)
        REFERENCES Kupac(kupac_PIB)
);
CREATE OR REPLACE TRIGGER IzmenaNazivaKupcaNaOsnovuPIB_a
BEFORE UPDATE OF kupac_PIB ON Kontakt
FOR EACH ROW
DECLARE
kupac_PIB_tmp VARCHAR2(255);
BEGIN
        SELECT naziv_firme_kupac
          INTO kupac_PIB_tmp
          FROM Kupac
         WHERE kupac_PIB = :new.kupac_PIB;
         
        :new.naziv_firme_kupac := kupac_PIB_tmp;
END;
/
INSERT INTO Kupac
SELECT 1, 'abcd' from dual union all
SELECT 2, 'efgh' from dual;
2 rows affected

INSERT INTO Kontakt(mail, telefon, kupac_PIB, partner_PIB, naziv_firme_kupac, naziv_poslovni_partner)
SELECT 'abcd@efg.com', '123456', 1, 1, 'wxyz', 'abcd' from dual;
1 rows affected

UPDATE Kontakt
   SET kupac_PIB = 2
 WHERE naziv_firme_kupac = 'wxyz';
1 rows affected

SELECT * FROM Kontakt;


ID_KONTAKT
MAIL
TELEFON
KUPAC_PIB
PARTNER_PIB
NAZIV_FIRME_KUPAC
NAZIV_POSLOVNI_PARTNER


1
abcd@efg.com
123456
2
1
efgh
abcd