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

时间:2021-07-01 10:21:17 帮助过:65人阅读

问题导读: 1.NTILE作用是什么? 2.按照pv降序排列,生成分组内每天的pv名次可使用哪个窗口函数? 3.RANK 和 DENSE_RANK作用是什么? 接上篇:Hive分析窗口函数(一)SUM,AVG,MIN,MAX 本文中介绍前几个序列函数,NTILE,ROW_NUMBER,RANK,DENSE_RANK,下面会一


问题导读:
1.NTILE作用是什么?
2.按照pv降序排列,生成分组内每天的pv名次可使用哪个窗口函数?
3.RANK 和 DENSE_RANK作用是什么?

接上篇:Hive分析窗口函数(一)SUM,AVG,MIN,MAX


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

注意: 序列函数不支持WINDOW子句。
(什么是WINDOW子句,Hive分析窗口函数(一)SUM,AVG,MIN,MAX)

数据准备:


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
    cookie2,2015-04-10,2
    cookie2,2015-04-11,3
    cookie2,2015-04-12,5
    cookie2,2015-04-13,6
    cookie2,2015-04-14,3
    cookie2,2015-04-15,9
    cookie2,2015-04-16,7
     
    CREATE EXTERNAL TABLE lxw1234 (
    cookieid string,
    createtime string, --day
    pv INT
    ) ROW FORMAT DELIMITED
    FIELDS TERMINATED BY ','
    stored as textfile location '/tmp/lxw11/';
     
    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
    cookie2 2015-04-10 2
    cookie2 2015-04-11 3
    cookie2 2015-04-12 5
    cookie2 2015-04-13 6
    cookie2 2015-04-14 3
    cookie2 2015-04-15 9
    cookie2 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


 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。

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

  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。

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