处理时间时用到了，记录一下。

时间差天数

select ‘2017-12-10’::date – ‘2017-12-01’::date;

时间差秒数

select extract(epoch FROM (now() – (now()-interval ‘1 day’) ));
select trunc(extract(epoch FROM (now() – (now()-interval ‘1 day’) ))::numeric);
select trunc(extract(epoch FROM (now() – (now()-interval ‘1 day’) ))::numeric,1);
select round(extract(epoch FROM (now() – (now()-interval ‘1 day’) ))::numeric);
select round(extract(epoch FROM (now() – (now()-interval ‘1 day’) ))::numeric,1);