Data
cookie4.txt
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 table cookie4(cookieid string, createtime string, url string)
row format delimited fields terminated by ',';
load data local inpath "/home/hadoop/apps/tt" into table cookie4;
select * from cookie4;
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)
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,
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 cookie4;
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
LAST_VALUE function FIRST_VALUE and
after sorting the packets take FIRST_VALUE, as of the current line, the first value
LAST_VALUE after taking the sorted packets to the current cut-off line, a value of the last
two functions is frequently used (and are often used in conjunction with ordering ), more practical!
select
cookieid,
createtime,
url,
first_value(url) over (partition by cookieid order by createtime) as rn,
last_value(url) over (partition by cookieid order by createtime) as last_1_time
from cookie4;