求一段sql

[_小黑_]

year	month	channel				product		week qty	datatype	qtytype	date
2018	5	Chain and Dept. Store	02233710	18	0	Display_Inv	Actual	2019-02-13 10:49:40.773
2018	5	Chain and Dept. Store	02233710	19	0	Display_Inv	Actual	2019-02-13 10:49:40.773
2018	5	Chain and Dept. Store	02233710	21	0	Display_Inv	Actual	2019-02-13 10:49:40.773
2018	5	Chain and Dept. Store	02439713	18	0	Display_Inv	Actual	2019-02-13 10:49:40.773
2018	5	Chain and Dept. Store	02439713	21	0	Display_Inv	Actual	2019-02-13 10:49:40.773
--以上是数据表
--以下是想要的结果
year	month	channel				product		week qty	datatype	qtytype	date
2018	5	Chain and Dept. Store	02233710	21	0	Display_Inv	Actual	2019-02-13 10:49:40.773
2018	5	Chain and Dept. Store	02439713	21	0	Display_Inv	Actual	2019-02-13 10:49:40.773
求一段sql

[唐诗三百首]

select * 
 from [表名] a
 where not exists(select 1 
                  from [表名] b
				  where b.year=a.year
				  and b.month=a.month
				  and b.channel=a.channel
				  and b.product=a.product
				  and b.week>a.week)

[中国风]

e.g.

SELECT *
FROM
(SELECT *
       ,ROW_NUMBER() OVER (PARTITION BY year, month, channel, product ORDER BY week DESC) AS RN
 FROM tab) AS T
WHERE RN=1