求一个表值函数，通过一个日期，可以返回这个日期所在周的7天日期，
例：比如传入‘2015-05-16’，我要得到
2015-05-11
2015-05-12
。。。
2015-05-17
------解决思路----------------------
create function fn_getWeek(@date smalldatetime)
returns @tab table(redate smalldatetime)
as begin
INSERT INTO @tab
SELECT DATEADD(DD,NUMBER-(DATEPART(WEEKDAY,@date)-1),@date) FROM MASTER.DBO.spt_values A,
(SELECT DATEPART(WEEKDAY,@date)-1 AS TEST_DATE) AS B
WHERE TYPE='P' AND NUMBER>=1 AND NUMBER<=7
return
end