SQL如何經過當前日期獲取上週一日期【轉】

--當前時間 
select getdate()
--當前時間周的起始日期（以週一爲例）
select DATEADD(week,DATEDIFF(week,0,getdate()),0)
--上週起始：
select dateadd(week,-1,DATEADD(week,DATEDIFF(week,0,getdate()),0))
--上上週起始：
select dateadd(week,-2,DATEADD(week,DATEDIFF(week,0,getdate()),0))
--上上上週起始：s
elect dateadd(week,-3,DATEADD(week,DATEDIFF(week,0,getdate()),0))