select months_between(to_date('1997-03-15','yyyy-mm-dd'),to_date('1983-03-15','yyyy-mm-dd')) from dual;-----返回168
select months_between(to_date('1983-03-15','yyyy-mm-dd'),to_date('1997-03-15','yyyy-mm-dd')) from dual;-----返回-168
select months_between(to_date('1997-03-15','yyyy-mm-dd'),to_date('1983-03-15','yyyy-mm-dd')) from dual;-----返回168
select months_between(to_date('1983-03-15','yyyy-mm-dd'),to_date('1997-03-15','yyyy-mm-dd')) from dual;-----返回-168