How to subtract seconds from postgres datetime

Question

Say I have column of type dateTime with value "2014-04-14 12:17:55.772" & I need to subtract seconds "2" seconds from it to get o/p like this "12:17:53".

Answer 1

select '2014-04-14 12:17:55.772'::timestamp - interval '2 seconds';

For greater flexibility it is possible to mutiply the interval

select '2014-04-14 12:17:55.772'::timestamp - 2 * interval '1 second';

If you want to truncate to the second

select date_trunc(
    'second', 
    '2014-04-14 12:17:55.772'::timestamp - interval '2 seconds'
);