Hive分析窗口函数(二) NTILE,ROW_NUMBER,RANK,DENSE_RANK

Hive版本为 apache-hive-0.13.1

备注:序列函数不支持WINDOW子句

数据准备:

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CREATE EXTERNAL TABLE lxw1234 (
cookieid string,
createtime string, --day
pv int
) ROW FORMAT DELIMITED
FIELDS TERMINATED BY ','
stored as textfile location '/tmp/lxw11/';

hive> DESC lxw1234;
cookieid string
createtime string
pv int

hive> select * from lxw1234;
OK
cookie1 2015-04-10 1
cookie1 2015-04-11 5
cookie1 2015-04-12 7
cookie1 2015-04-13 3
cookie1 2015-04-14 2
cookie1 2015-04-15 4
cookie1 2015-04-16 4

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

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SELECT 
cookieid,
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 lxw1234
ORDER BY cookieid,createtime;

cookieid day pv rn1 rn2 rn3
-------------------------------------------------
cookie1 2015-04-10 1 1 1 1
cookie1 2015-04-11 5 1 1 1
cookie1 2015-04-12 7 1 1 2
cookie1 2015-04-13 3 1 2 2
cookie1 2015-04-14 2 2 2 3
cookie1 2015-04-15 4 2 3 3
cookie1 2015-04-16 4 2 3 4
cookie2 2015-04-10 2 1 1 1
cookie2 2015-04-11 3 1 1 1
cookie2 2015-04-12 5 1 1 2
cookie2 2015-04-13 6 1 2 2
cookie2 2015-04-14 3 2 2 3
cookie2 2015-04-15 9 2 3 4
cookie2 2015-04-16 7 2 3 4
–比如,统计一个cookie,pv数最多的前1/3的天

SELECT
cookieid,
createtime,
pv,
NTILE(3) OVER(PARTITION BY cookieid ORDER BY pv DESC) AS rn
FROM lxw1234;

--rn = 1 的记录,就是我们想要的结果

cookieid day pv rn
----------------------------------
cookie1 2015-04-12 7 1
cookie1 2015-04-11 5 1
cookie1 2015-04-15 4 1
cookie1 2015-04-16 4 2
cookie1 2015-04-13 3 2
cookie1 2015-04-14 2 3
cookie1 2015-04-10 1 3
cookie2 2015-04-15 9 1
cookie2 2015-04-16 7 1
cookie2 2015-04-13 6 1
cookie2 2015-04-12 5 2
cookie2 2015-04-14 3 2
cookie2 2015-04-11 3 3
cookie2 2015-04-10 2 3

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。

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SELECT 
cookieid,
createtime,
pv,
ROW_NUMBER() OVER(PARTITION BY cookieid ORDER BY pv desc) AS rn
FROM lxw1234;

cookieid day pv rn
-------------------------------------------
cookie1 2015-04-12 7 1
cookie1 2015-04-11 5 2
cookie1 2015-04-15 4 3
cookie1 2015-04-16 4 4
cookie1 2015-04-13 3 5
cookie1 2015-04-14 2 6
cookie1 2015-04-10 1 7
cookie2 2015-04-15 9 1
cookie2 2015-04-16 7 2
cookie2 2015-04-13 6 3
cookie2 2015-04-12 5 4
cookie2 2015-04-14 3 5
cookie2 2015-04-11 3 6
cookie2 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

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SELECT 
cookieid,
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 rn3
FROM lxw1234
WHERE cookieid = 'cookie1';

cookieid day pv rn1 rn2 rn3
--------------------------------------------------
cookie1 2015-04-12 7 1 1 1
cookie1 2015-04-11 5 2 2 2
cookie1 2015-04-15 4 3 3 3
cookie1 2015-04-16 4 3 3 4
cookie1 2015-04-13 3 5 4 5
cookie1 2015-04-14 2 6 5 6
cookie1 2015-04-10 1 7 6 7

rn1: 15号和16号并列第3, 13号排第5
rn2: 15号和16号并列第3, 13号排第4
rn3: 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。