在sqlserver数据库中，如何得到当前日期任意天前的日期？

[lishijie910123]

例如今天是2007-9-13，
我要得到一天前，两天前 ，一个星期前，一个月前。。。。。
的日期，
这个是在做查询是要用到的，麻烦高手指点一下！
小弟不胜感激！

[dobear_0922]

declare @ndays int
set @ndays=3
select dateadd(day,-@ndays,getdate())

-----------------------
2007-09-10 14:23:18.830

(1 row(s) affected)

[liangjianshi]

dataadd()函数

[dobear_0922]

declare @ndays int,
@nweeks int,
@nmonths int
select @ndays=3,@nweeks=3,@nmonths=3
select dateadd(day,-@ndays,getdate()) as SomedaysAgo
,dateadd(wk,-@nweeks,getdate()) as SomeweekssAgo
,dateadd(m,-@nmonths,getdate()) as SomemothsAgo
/******
SomedaysAgo SomeweekssAgo SomemothsAgo
----------------------- ----------------------- -----------------------
2007-09-10 14:26:30.690 2007-08-23 14:26:30.690 2007-06-13 14:26:30.690
**********/

[kelph]

DATEADD (datepart , number, date )