date difference in postgressql code example

Example 1: postgresql get difference in hours between two dates

select EXTRACT(
	EPOCH FROM now() - (now() - INTERVAL '5 HOUR')
)/3600

-- it will return 5

Example 2: postgresql get difference between two dates

select age('2010-04-01', '2012-03-05'),
       date_part('year',age('2010-04-01', '2012-03-05')),
       date_part('month',age('2010-04-01', '2012-03-05')),
       date_part('day',age('2010-04-01', '2012-03-05'));