get datediff in days float psql code example

Example: 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'));