获取某时间段的数据

declare   @dt   datetime
set   @dt= '2004/08/25 '

--一周內
select   *   from   tb   where   datediff(day,@dt,getdate()) <=7     --@dt相當於日期字段

--一個月內
select   *   from   tb   where   datediff(month,@dt,getdate()) <=1

--半年內
select   *   from   tb   where   datediff(month,@dt,getdate()) <=6