MONTHS_BETWEEN

MONTHS_BETWEEN function returns the number of months between two dates.

Syntax: MONTHS_BETWEEN(date_expression1,date_expression2);

Months Between Function Details

MONTHS_BETWEEN function returns an integer number if the days are the same.

SELECT MONTHS_BETWEEN (DATE '2012-02-12', DATE '2012-01-12') FROM DUAL; 

MONTHS_BETWEEN function returns an integer number if the both dates specify the last day of the month.

SELECT MONTHS_BETWEEN (DATE '2012-02-29', DATE '2012-01-31') FROM DUAL; 

MONTHS_BETWEEN function returns a decimal number if the days are different.

SELECT MONTHS_BETWEEN (DATE '2012-02-29', DATE '2012-02-01') FROM DUAL;

MONTHS_BETWEEN always calculates the fractional part as the difference in days divided by 31

In the example above, the fractional part is calculated as (29 - 1)/31 = 0.903225806, although there are 29 days in February 2012.

You can also see that MONTHS_BETWEEN does not return an integer result if you specify the first and last days of the same month.