如何统计周数据?

[叶子哟]

表中两个字段a,b,其中a为日期型,b为记录此条记录的销售量,请问如何统计一年或一月中各周的数据和?
如果为:
第n周 数据和
第n+1周 数据和
...

[playyuer]

select datediff(week,a,getdate()),min(a),sum(b)
from T
group by datediff(week,a,getdate())

[叶子哟]

非常感谢,但这样子只对一个月有意义,对两个,三个月的...,能不能反应出是当月的第几周

[playyuer]

某个月的第一周的定义:
第一个星期一所在的那一周是该月的第一周吗?

[zjcxc]

--统计一年中的.
select 周数=datepart(week,a),b=sum(b) from t group by datepart(week,a)

--分月统计的.
select 月份=convert(varchar(6),a,112)
,周数=datepart(week,a)-datepart(week,a-day(a))+1,
,b=sum(b)
from t
group by convert(varchar(6),a,112),datepart(week,a)-datepart(week,a-day(a))+1

[playyuer]

select dateadd(day,-datepart(weekday,min(a))+2,min(a)) as 周一
,dateadd(day,8-datepart(weekday,min(a)),min(a)) as 周日
,sum(b)
from T
group by datediff(week,a,getdate())
order by min(a)

[叶子哟]

非常感谢两位,给分