The following query calculates the difference in days between the two DATE values.
SELECT (DATE '2007-05-10' - DATE '2007-04-28') DAY;
The result is the following:
(2007-05-10 - 2007-04-28) DAY ----------------------------- 12
The following query calculates the difference in months between the two DATE values.
SELECT (DATE '2007-05-10' - DATE '2007-04-28') MONTH;
The result is the following:
(2007-05-10 - 2007-04-28) MONTH ------------------------------- 1
There is a difference of 12 days between the two dates, which does not constitute one month. However, Vantage ignores the day values during the calculation and only considers the month values, so the result is an interval of one month indicating the difference between April and May.