Hive的窗口函数
这老哥的窗口函数总结的十分不错，我就拿来主义了，附上地址 http://lxw1234.com/archives/2015/04/190.htm
数据准备
cookie1,2015-04-10 10:00:02,url2
cookie1,2015-04-10 10:00:00,url1
cookie1,2015-04-10 10:03:04,1url3
cookie1,2015-04-10 10:50:05,url6
cookie1,2015-04-10 11:00:00,url7
cookie1,2015-04-10 10:10:00,url4
cookie1,2015-04-10 10:50:01,url5
cookie2,2015-04-10 10:00:02,url22
cookie2,2015-04-10 10:00:00,url11
cookie2,2015-04-10 10:03:04,1url33
cookie2,2015-04-10 10:50:05,url66
cookie2,2015-04-10 11:00:00,url77
cookie2,2015-04-10 10:10:00,url44
cookie2,2015-04-10 10:50:01,url55
CREATE EXTERNAL TABLE lxw1234 (
cookieid string,
createtime string, --页面访问时间
url STRING --被访问页面
) ROW FORMAT DELIMITED
FIELDS TERMINATED BY ','
stored as textfile location '/tmp/lxw11/';
hive> select * from lxw1234;
OK
cookie1 2015-04-10 10:00:02 url2
cookie1 2015-04-10 10:00:00 url1
cookie1 2015-04-10 10:03:04 1url3
cookie1 2015-04-10 10:50:05 url6
cookie1 2015-04-10 11:00:00 url7
cookie1 2015-04-10 10:10:00 url4
cookie1 2015-04-10 10:50:01 url5
cookie2 2015-04-10 10:00:02 url22
cookie2 2015-04-10 10:00:00 url11
cookie2 2015-04-10 10:03:04 1url33
cookie2 2015-04-10 10:50:05 url66
cookie2 2015-04-10 11:00:00 url77
cookie2 2015-04-10 10:10:00 url44
cookie2 2015-04-10 10:50:01 url55
LAG
LAG(col,n,DEFAULT) 用于统计窗口内往上第n行值
第一个参数为列名，第二个参数为往上第n行（可选，默认为1），第三个参数为默认值（当往上第n行为NULL时候，取默认值，如不指定，则为NULL）
SELECT cookieid,
createtime,
url,
ROW_NUMBER() OVER(PARTITION BY cookieid ORDER BY createtime) AS rn,
LAG(createtime,1,'1970-01-01 00:00:00') OVER(PARTITION BY cookieid ORDER BY createtime) AS last_1_time,
LAG(createtime,2) OVER(PARTITION BY cookieid ORDER BY createtime) AS last_2_time
FROM lxw1234;
cookieid createtime url rn last_1_time last_2_time
\-------------------------------------------------------------------------------------------
cookie1 2015-04-10 10:00:00 url1 1 1970-01-01 00:00:00 NULL
cookie1 2015-04-10 10:00:02 url2 2 2015-04-10 10:00:00 NULL
cookie1 2015-04-10 10:03:04 1url3 3 2015-04-10 10:00:02 2015-04-10 10:00:00
cookie1 2015-04-10 10:10:00 url4 4 2015-04-10 10:03:04 2015-04-10 10:00:02
cookie1 2015-04-10 10:50:01 url5 5 2015-04-10 10:10:00 2015-04-10 10:03:04
cookie1 2015-04-10 10:50:05 url6 6 2015-04-10 10:50:01 2015-04-10 10:10:00
cookie1 2015-04-10 11:00:00 url7 7 2015-04-10 10:50:05 2015-04-10 10:50:01
cookie2 2015-04-10 10:00:00 url11 1 1970-01-01 00:00:00 NULL
cookie2 2015-04-10 10:00:02 url22 2 2015-04-10 10:00:00 NULL
cookie2 2015-04-10 10:03:04 1url33 3 2015-04-10 10:00:02 2015-04-10 10:00:00
cookie2 2015-04-10 10:10:00 url44 4 2015-04-10 10:03:04 2015-04-10 10:00:02
cookie2 2015-04-10 10:50:01 url55 5 2015-04-10 10:10:00 2015-04-10 10:03:04
cookie2 2015-04-10 10:50:05 url66 6 2015-04-10 10:50:01 2015-04-10 10:10:00
cookie2 2015-04-10 11:00:00 url77 7 2015-04-10 10:50:05 2015-04-10 10:50:01
last_1_time: 指定了往上第1行的值， default 为'1970-01-01 00:00:00'
cookie1第一行，往上1行为NULL,因此取默认值 1970-01-01 00:00:00
cookie1第三行，往上1行值为第二行值，2015-04-10 10:00:02
cookie1第六行，往上1行值为第五行值，2015-04-10 10:50:01
last_2_time: 指定了往上第2行的值，为指定默认值
cookie1第一行，往上2行为NULL
cookie1第二行，往上2行为NULL
cookie1第四行，往上2行为第二行值，2015-04-10 10:00:02
cookie1第七行，往上2行为第五行值，2015-04-10 10:50:01
LEAD
与LAG相反
LEAD(col,n,DEFAULT) 用于统计窗口内往下第n行值
第一个参数为列名，第二个参数为往下第n行（可选，默认为1），第三个参数为默认值（当往下第n行为NULL时候，取默认值，如不指定，则为NULL）
SELECT cookieid,
createtime,
url,
ROW_NUMBER() OVER(PARTITION BY cookieid ORDER BY createtime) AS rn,
LEAD(createtime,1,'1970-01-01 00:00:00') OVER(PARTITION BY cookieid ORDER BY createtime) AS next_1_time,
LEAD(createtime,2) OVER(PARTITION BY cookieid ORDER BY createtime) AS next_2_time
FROM lxw1234;
cookieid createtime url rn next_1_time next_2_time
\-------------------------------------------------------------------------------------------
cookie1 2015-04-10 10:00:00 url1 1 2015-04-10 10:00:02 2015-04-10 10:03:04
cookie1 2015-04-10 10:00:02 url2 2 2015-04-10 10:03:04 2015-04-10 10:10:00
cookie1 2015-04-10 10:03:04 1url3 3 2015-04-10 10:10:00 2015-04-10 10:50:01
cookie1 2015-04-10 10:10:00 url4 4 2015-04-10 10:50:01 2015-04-10 10:50:05
cookie1 2015-04-10 10:50:01 url5 5 2015-04-10 10:50:05 2015-04-10 11:00:00
cookie1 2015-04-10 10:50:05 url6 6 2015-04-10 11:00:00 NULL
cookie1 2015-04-10 11:00:00 url7 7 1970-01-01 00:00:00 NULL
cookie2 2015-04-10 10:00:00 url11 1 2015-04-10 10:00:02 2015-04-10 10:03:04
cookie2 2015-04-10 10:00:02 url22 2 2015-04-10 10:03:04 2015-04-10 10:10:00
cookie2 2015-04-10 10:03:04 1url33 3 2015-04-10 10:10:00 2015-04-10 10:50:01
cookie2 2015-04-10 10:10:00 url44 4 2015-04-10 10:50:01 2015-04-10 10:50:05
cookie2 2015-04-10 10:50:01 url55 5 2015-04-10 10:50:05 2015-04-10 11:00:00
cookie2 2015-04-10 10:50:05 url66 6 2015-04-10 11:00:00 NULL
cookie2 2015-04-10 11:00:00 url77 7 1970-01-01 00:00:00 NULL
--逻辑与LAG一样，只不过LAG是往上，LEAD是往下。
FIRST_VALUE
取分组内排序后，截止到当前行，第一个值
SELECT cookieid,
createtime,
url,
ROW_NUMBER() OVER(PARTITION BY cookieid ORDER BY createtime) AS rn,
FIRST_VALUE(url) OVER(PARTITION BY cookieid ORDER BY createtime) AS first1
FROM lxw1234;
cookieid createtime url rn first1
\---------------------------------------------------------
cookie1 2015-04-10 10:00:00 url1 1 url1
cookie1 2015-04-10 10:00:02 url2 2 url1
cookie1 2015-04-10 10:03:04 1url3 3 url1
cookie1 2015-04-10 10:10:00 url4 4 url1
cookie1 2015-04-10 10:50:01 url5 5 url1
cookie1 2015-04-10 10:50:05 url6 6 url1
cookie1 2015-04-10 11:00:00 url7 7 url1
cookie2 2015-04-10 10:00:00 url11 1 url11
cookie2 2015-04-10 10:00:02 url22 2 url11
cookie2 2015-04-10 10:03:04 1url33 3 url11
cookie2 2015-04-10 10:10:00 url44 4 url11
cookie2 2015-04-10 10:50:01 url55 5 url11
cookie2 2015-04-10 10:50:05 url66 6 url11
cookie2 2015-04-10 11:00:00 url77 7 url11
LAST_VALUE
取分组内排序后，截止到当前行，最后一个值
SELECT cookieid,
createtime,
url,
ROW_NUMBER() OVER(PARTITION BY cookieid ORDER BY createtime) AS rn,
LAST_VALUE(url) OVER(PARTITION BY cookieid ORDER BY createtime) AS last1
FROM lxw1234;
cookieid createtime url rn last1
\-----------------------------------------------------------------
cookie1 2015-04-10 10:00:00 url1 1 url1
cookie1 2015-04-10 10:00:02 url2 2 url2
cookie1 2015-04-10 10:03:04 1url3 3 1url3
cookie1 2015-04-10 10:10:00 url4 4 url4
cookie1 2015-04-10 10:50:01 url5 5 url5
cookie1 2015-04-10 10:50:05 url6 6 url6
cookie1 2015-04-10 11:00:00 url7 7 url7
cookie2 2015-04-10 10:00:00 url11 1 url11
cookie2 2015-04-10 10:00:02 url22 2 url22
cookie2 2015-04-10 10:03:04 1url33 3 1url33
cookie2 2015-04-10 10:10:00 url44 4 url44
cookie2 2015-04-10 10:50:01 url55 5 url55
cookie2 2015-04-10 10:50:05 url66 6 url66
cookie2 2015-04-10 11:00:00 url77 7 url77
如果不指定ORDER BY，则默认按照记录在文件中的偏移量进行排序，会出现错误的结果
SELECT cookieid,
createtime,
url,
FIRST_VALUE(url) OVER(PARTITION BY cookieid) AS first2
FROM lxw1234;
cookieid createtime url first2
\----------------------------------------------
cookie1 2015-04-10 10:00:02 url2 url2
cookie1 2015-04-10 10:00:00 url1 url2
cookie1 2015-04-10 10:03:04 1url3 url2
cookie1 2015-04-10 10:50:05 url6 url2
cookie1 2015-04-10 11:00:00 url7 url2
cookie1 2015-04-10 10:10:00 url4 url2
cookie1 2015-04-10 10:50:01 url5 url2
cookie2 2015-04-10 10:00:02 url22 url22
cookie2 2015-04-10 10:00:00 url11 url22
cookie2 2015-04-10 10:03:04 1url33 url22
cookie2 2015-04-10 10:50:05 url66 url22
cookie2 2015-04-10 11:00:00 url77 url22
cookie2 2015-04-10 10:10:00 url44 url22
cookie2 2015-04-10 10:50:01 url55 url22
SELECT cookieid,
createtime,
url,
LAST_VALUE(url) OVER(PARTITION BY cookieid) AS last2
FROM lxw1234;
cookieid createtime url last2
\----------------------------------------------
cookie1 2015-04-10 10:00:02 url2 url5
cookie1 2015-04-10 10:00:00 url1 url5
cookie1 2015-04-10 10:03:04 1url3 url5
cookie1 2015-04-10 10:50:05 url6 url5
cookie1 2015-04-10 11:00:00 url7 url5
cookie1 2015-04-10 10:10:00 url4 url5
cookie1 2015-04-10 10:50:01 url5 url5
cookie2 2015-04-10 10:00:02 url22 url55
cookie2 2015-04-10 10:00:00 url11 url55
cookie2 2015-04-10 10:03:04 1url33 url55
cookie2 2015-04-10 10:50:05 url66 url55
cookie2 2015-04-10 11:00:00 url77 url55
cookie2 2015-04-10 10:10:00 url44 url55
cookie2 2015-04-10 10:50:01 url55 url55
如果想要取分组内排序后最后一个值，则需要变通一下：
SELECT cookieid,
createtime,
url,
ROW_NUMBER() OVER(PARTITION BY cookieid ORDER BY createtime) AS rn,
LAST_VALUE(url) OVER(PARTITION BY cookieid ORDER BY createtime) AS last1,
FIRST_VALUE(url) OVER(PARTITION BY cookieid ORDER BY createtime DESC) AS last2
FROM lxw1234
ORDER BY cookieid,createtime;
cookieid createtime url rn last1 last2
\-------------------------------------------------------------
cookie1 2015-04-10 10:00:00 url1 1 url1 url7
cookie1 2015-04-10 10:00:02 url2 2 url2 url7
cookie1 2015-04-10 10:03:04 1url3 3 1url3 url7
cookie1 2015-04-10 10:10:00 url4 4 url4 url7
cookie1 2015-04-10 10:50:01 url5 5 url5 url7
cookie1 2015-04-10 10:50:05 url6 6 url6 url7
cookie1 2015-04-10 11:00:00 url7 7 url7 url7
cookie2 2015-04-10 10:00:00 url11 1 url11 url77
cookie2 2015-04-10 10:00:02 url22 2 url22 url77
cookie2 2015-04-10 10:03:04 1url33 3 1url33 url77
cookie2 2015-04-10 10:10:00 url44 4 url44 url77
cookie2 2015-04-10 10:50:01 url55 5 url55 url77
cookie2 2015-04-10 10:50:05 url66 6 url66 url77
cookie2 2015-04-10 11:00:00 url77 7 url77 url77
提示：在使用分析函数的过程中，要特别注意ORDER BY子句，用的不恰当，统计出的结果就不是你所期望的。
