Função Oracle MONTHS BETWEEN

SELECT MONTHS_BETWEEN(TO_DATE('28/12/2017', 'DD/MM/YY'),
                      TO_DATE('03/08/2017', 'DD/MM/YY')) AS MONTHS_BETWEEN
 FROM dual;

SELECT TRUNC(MONTHS_BETWEEN(TO_DATE('28/12/2017', 'DD/MM/YY'),
                            TO_DATE('03/08/2017', 'DD/MM/YY'))) AS MONTHS_BETWEEN
 FROM dual;

SELECT ROUND(MONTHS_BETWEEN(TO_DATE('28/12/2017', 'DD/MM/YY'),
                            TO_DATE('03/08/2017', 'DD/MM/YY'))) AS MONTHS_BETWEEN
 FROM dual;