CREATE OR REPLACE PACKAGE PACKAGE DATUMY AS

  FUNCTION datumy_rozdil(datum_od DATE, datum_do DATE, typ CHAR) RETURN NUMBER;

  FUNCTION pracovni_den(datum DATE) RETURN NUMBER;

  FUNCTION den_v_mesici(datum DATE, prvni NUMBER) RETURN DATE;

END DATUMY;

CREATE OR REPLACE PACKAGE BODY DATUMY AS

    FUNCTION datumy_rozdil(datum_od DATE, datum_do DATE, typ CHAR)
    RETURN NUMBER AS rozdil NUMBER;
    BEGIN
        IF datum_od IS NOT NULL AND datum_do IS NOT NULL AND typ IN ('D','H','M','S') THEN
            rozdil := datum_do - datum_od;
            CASE typ
                WHEN 'D' THEN
                    RETURN ROUND(rozdil, 2);
                WHEN 'H' THEN
                    RETURN ROUND(rozdil*24,2);
                WHEN 'M' THEN
                    RETURN ROUND(rozdil*24*60,2);
                WHEN 'S' THEN
                    RETURN ROUND(rozdil*24*60*60,2);
            END CASE;
        ELSE
            raise_application_error(-20000, 'Špatné parametry');
        END IF;
    EXCEPTION
        WHEN OTHERS THEN RETURN NULL;
    END datumy_rozdil;
END DATUMY;