本文中介紹前幾個序列函數，NTILE,ROW_NUMBER,RANK,DENSE_RANK，下面會一一解釋各自的用途。
Hive版本為 apache-hive-0.13.1
數據準備：

cookie1,2015-04-10,1cookie1,2015-04-11,5cookie1,2015-04-12,7cookie1,2015-04-13,3cookie1,2015-04-14,2cookie1,2015-04-15,4cookie1,2015-04-16,4cookie2,2015-04-10,2cookie2,2015-04-11,3cookie2,2015-04-12,5cookie2,2015-04-13,6cookie2,2015-04-14,3cookie2,2015-04-15,9cookie2,2015-04-16,7CREATE EXTERNAL TABLE lxw1234 (cookieid string,createtime string, --daypv INT) ROW FORMAT DELIMITEDFIELDS TERMINATED BY ','stored as textfile location '/tmp/lxw11/';DESC lxw1234;cookieid STRINGcreatetime STRINGpv INThive> select * from lxw1234;OKcookie1 2015-04-10 1cookie1 2015-04-11 5cookie1 2015-04-12 7cookie1 2015-04-13 3cookie1 2015-04-14 2cookie1 2015-04-15 4cookie1 2015-04-16 4cookie2 2015-04-10 2cookie2 2015-04-11 3cookie2 2015-04-12 5cookie2 2015-04-13 6cookie2 2015-04-14 3cookie2 2015-04-15 9cookie2 2015-04-16 7

NTILE
NTILE(n)，用于將分組數據按照順序切分成n片，返回當前切片值
NTILE不支持ROWS BETWEEN，比如 NTILE(2) OVER(PARTITION BY cookieid ORDER BY createtime ROWS BETWEEN 3 PRECEDING AND CURRENT ROW)
如果切片不均勻，默認增加第一個切片的分布

SELECTcookieid,createtime,pv,NTILE(2) OVER(PARTITION BY cookieid ORDER BY createtime) AS rn1, --分組內將數據分成2片NTILE(3) OVER(PARTITION BY cookieid ORDER BY createtime) AS rn2, --分組內將數據分成3片NTILE(4) OVER(ORDER BY createtime) AS rn3 --將所有數據分成4片FROM lxw1234ORDER BY cookieid,createtime;cookieid day pv rn1 rn2 rn3-------------------------------------------------cookie1 2015-04-10 1 1 1 1cookie1 2015-04-11 5 1 1 1cookie1 2015-04-12 7 1 1 2cookie1 2015-04-13 3 1 2 2cookie1 2015-04-14 2 2 2 3cookie1 2015-04-15 4 2 3 3cookie1 2015-04-16 4 2 3 4cookie2 2015-04-10 2 1 1 1cookie2 2015-04-11 3 1 1 1cookie2 2015-04-12 5 1 1 2cookie2 2015-04-13 6 1 2 2cookie2 2015-04-14 3 2 2 3cookie2 2015-04-15 9 2 3 4cookie2 2015-04-16 7 2 3 4

?比如，統計一個cookie，pv數最多的前1/3的天

SELECTcookieid,createtime,pv,NTILE(3) OVER(PARTITION BY cookieid ORDER BY pv DESC) AS rnFROM lxw1234;--rn = 1 的記錄，就是我們想要的結果cookieid day pv rn----------------------------------cookie1 2015-04-12 7 1cookie1 2015-04-11 5 1cookie1 2015-04-15 4 1cookie1 2015-04-16 4 2cookie1 2015-04-13 3 2cookie1 2015-04-14 2 3cookie1 2015-04-10 1 3cookie2 2015-04-15 9 1cookie2 2015-04-16 7 1cookie2 2015-04-13 6 1cookie2 2015-04-12 5 2cookie2 2015-04-14 3 2cookie2 2015-04-11 3 3cookie2 2015-04-10 2 3

ROW_NUMBER

ROW_NUMBER() –從1開始，按照順序，生成分組內記錄的序列
–比如，按照pv降序排列，生成分組內每天的pv名次
ROW_NUMBER() 的應用場景非常多，再比如，獲取分組內排序第一的記錄;獲取一個session中的第一條refer等。

SELECTcookieid,createtime,pv,ROW_NUMBER() OVER(PARTITION BY cookieid ORDER BY pv desc) AS rnFROM lxw1234;cookieid day pv rn-------------------------------------------cookie1 2015-04-12 7 1cookie1 2015-04-11 5 2cookie1 2015-04-15 4 3cookie1 2015-04-16 4 4cookie1 2015-04-13 3 5cookie1 2015-04-14 2 6cookie1 2015-04-10 1 7cookie2 2015-04-15 9 1cookie2 2015-04-16 7 2cookie2 2015-04-13 6 3cookie2 2015-04-12 5 4cookie2 2015-04-14 3 5cookie2 2015-04-11 3 6cookie2 2015-04-10 2 7

RANK 和 DENSE_RANK
—RANK() 生成數據項在分組中的排名，排名相等會在名次中留下空位
—DENSE_RANK() 生成數據項在分組中的排名，排名相等會在名次中不會留下空位

SELECTcookieid,createtime,pv,RANK() OVER(PARTITION BY cookieid ORDER BY pv desc) AS rn1,DENSE_RANK() OVER(PARTITION BY cookieid ORDER BY pv desc) AS rn2,ROW_NUMBER() OVER(PARTITION BY cookieid ORDER BY pv DESC) AS rn3FROM lxw1234WHERE cookieid = 'cookie1';cookieid day pv rn1 rn2 rn3--------------------------------------------------cookie1 2015-04-12 7 1 1 1cookie1 2015-04-11 5 2 2 2cookie1 2015-04-15 4 3 3 3cookie1 2015-04-16 4 3 3 4cookie1 2015-04-13 3 5 4 5cookie1 2015-04-14 2 6 5 6cookie1 2015-04-10 1 7 6 7rn1: 15號和16號并列第3, 13號排第5rn2: 15號和16號并列第3, 13號排第4rn3: 如果相等，則按記錄值排序，生成唯一的次序，如果所有記錄值都相等，或許會隨機排吧。

轉發:http://www.aboutyun.com/thread-12834-1-1.html

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