hive內group by取第一條數據，Hive中row_number的使用

1、hive的分組和組內排序---語法

語法：
row_number() over (partition by 字段a order by 計算項b desc ) rank

• rank是排序的別名
• partition by：類似hive的建表，分區的意思；
• order by ：排序，默認是升序，加desc降序；
• 這里按字段a分區，對計算項b進行降序排序

2、hive的分組和組內排序 --- 實例

要取top10品牌，各品牌的top10渠道，各品牌的top10渠道中各渠道的top10檔期

1、取top10品牌

select “品牌” , sum/count/其他() as num from "table_name" order by num desc limit 10;

2、取top10品牌下各品牌的top10渠道

select a.* from (select "品牌","渠道",sum/count() as num, row_number () over (partition by "品牌" order by num desc) rank from “table_name” where 品牌限制條件 group by “品牌”,“渠道” ) a having a.rank <= 10;

3、 取top10品牌下各品牌的top10渠道中各渠道的top10檔期

select a.* from (select "品牌","渠道","檔期",sum/count/其他() as num row_number() over (partition by "檔期" order by num desc) rank from "table_name" where 品牌限制條件 group by “品牌”,“渠道) a Having a.rank <= 10;

我的應用：rank編號，rank小組內從1開始編號

SELECT v.visitor_phone,v.city，v.bigarea,
row_number()over (partition by visitor_phone order by visitor_phone desc) rank 
from visitor v 
WHERE 1=1 and visitor_name in('蔣鳳','周金魁')
group BY v.visitor_phone,v.city
---------------------------------
18222666666 北京 華北區   1
18222666666 天津	華北區	2
13402777777 北京	華北區	1
13402777777 成都	中西部	2

取編號為1的

SELECT a.* from(
SELECT v.visitor_phone,v.city，v.bigarea,
row_number()over (partition by visitor_phone order by visitor_phone desc) rank 
from visitor v 
WHERE 1=1 and visitor_name in('蔣鳳','周金魁')
group BY v.visitor_phone,v.city
)a
where a.rank=1;
-------------------------------------
18222666666 北京 華北區   1
13402777777 北京 華北區	1