One, function introduction
It is used to calculate the time value after or before Y months above the time X (Y is a positive number to indicate after, and Y is a negative number to indicate before)
Two, usage examples
1. The current time two months ago:
select add_months(sysdate,-2) from dual;
2. The current point in time two months later:
select add_months(sysdate,2) from dual;