ADD_MONTHS returns a date that is a specified number of months after a specified date.
When the starting date is the last day of the month or when the returned month has fewer days, then
ADD_MONTHS returns the last day of the month. Otherwise, the returned day is the starting day.
date is the starting date.
integer is the number of months to be added to the starting date.
ADD_MONTHS('17-JUN-06', 1) returns the value