当前时间周的起始日期(以周一为例)select DATEADD(week,DATEDIFF(week,0,getdate()),0)上周起始:select dateadd(week,-1,DATEADD(week,DATEDIFF(week,0,getdate()),0))上上周起始:select dateadd(week,-2,DATEADD(week,DATEDIFF(week,0,getdate()),0))上上上周起始:select dateadd(week,-3,DATEADD(wee