本文中介绍前几个序列函数，NTILE,ROW_NUMBER,RANK,DENSE_RANK，下面会一一解释各自的用途。
Hive版本为 apache-hive-0.13.1
数据准备：

    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)，用于将分组数据按照顺序切分成n片，返回当前切片值
NTILE不支持ROWS BETWEEN，比如 NTILE(2) OVER(PARTITION BY cookieid ORDER BY createtime ROWS BETWEEN 3 PRECEDING AND CURRENT ROW)
如果切片不均匀，默认增加第一个切片的分布

SELECTcookieid,createtime,pv,NTILE(2) OVER(PARTITION BY cookieid ORDER BY createtime) AS rn1,        --分组内将数据分成2片NTILE(3) OVER(PARTITION BY cookieid ORDER BY createtime) AS rn2, --分组内将数据分成3片NTILE(4) OVER(ORDER BY createtime) AS rn3 --将所有数据分成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，统计一个cookie，pv数最多的前1/3的天

   SELECTcookieid,createtime,pv,NTILE(3) OVER(PARTITION BY cookieid ORDER BY pv DESC) AS rnFROM lxw1234;--rn = 1 的记录，就是我们想要的结果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() –从1开始，按照顺序，生成分组内记录的序列
–比如，按照pv降序排列，生成分组内每天的pv名次
ROW_NUMBER() 的应用场景非常多，再比如，获取分组内排序第一的记录;获取一个session中的第一条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() 生成数据项在分组中的排名，排名相等会在名次中留下空位
—DENSE_RANK() 生成数据项在分组中的排名，排名相等会在名次中不会留下空位

 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号和16号并列第3, 13号排第5rn2: 15号和16号并列第3, 13号排第4rn3: 如果相等，则按记录值排序，生成唯一的次序，如果所有记录值都相等，或许会随机排吧。

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