主题：用周分组后，如何再用 单号分组，统计所有单中的最大金额

sel ect b.[年份],b.[月份],b.[周次],b.[营业员姓名],MAX(b.[本周销售额])

from

(SELEC T 

cast(datename(year,a.[业务日期])as int) AS [年份],

cast(datename(month,a.[业务日期])as int) AS [月份],

cast(datename(week,a.[业务日期])as int) AS [周次],

a.[营业员姓名],

sum(a.[销售额]) as 本周销售额 ,

a.[单号]

FROM

dbo.worksheet as a

GROUP BY

cast(datename(year,a.[业务日期])as int) ,

cast(datename(month,a.[业务日期])as int) ,

cast(datename(week,a.[业务日期])as int) ,

a.[营业员姓名],

a.[单号]) as b

group by  b.[年份],b.[月份],b.[周次],b.[营业员姓名]