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)