日期常用取值

select date,

          to_number(to_char(date,'hh24')) 時,

          to_number(to_char(date,'mi')) 分,

          to_number(to_char(date,'ss')) 秒,

          to_number(to_char(date,'dd')) 日,

          to_number(to_char(date,'mm')) 月,

          to_number(to_char(date,'yyyy')) 年,

          to_number(to_char(date,'ddd')) 年內第幾天,

          trunc(date,'dd')  一天之始,

          trunc(date,'day')  周初,

          trunc(date,'mm')  月初,

          last_day(date) 月末,

          add_months(trunc(date,'mm'),1) 下月初,

          trunc(date,'yy')  年初,

          to_char(date,'day') 周幾,

          to_char(date,'month') 月份

from (select date+30/24/60/60+20/24/60+5/25 as date from tab where rownum<=1);