PGSQL的时间处理
两个日期做加减
date_part('day', cast(time1 as TIMESTAMP)- cast(time2 as TIMESTAMP))
to_date(字段1,'yyyMMdd') - to_date(字段2,'yyyMMdd')
算当天第几周
select extract(DOW from current_timestamp)
当天减去第几天
select to_char(current_timestamp - (select extract(DOW from current_timestamp) -1 || ‘day’):: interval)