SQL

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'));

Postgresql get diff between two dates in Months

EXTRACT(year FROM age(end_date,start_date))*12 + EXTRACT(month FROM age(end_date,start_date))

postgresql get difference in hours between two dates

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

-- it will return 5