hive 窗口函数（一）

窗口函数可以对数据进行分组，将数据按组分成一个个窗口。利用窗口函数可以对窗口内的数据进行排序，聚合操作，还可以通过window子句让窗口上下滑动，非常灵活。

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

create table  cookie1_sum
(
    cookieid   string,
    createtime string,
    pv         int
) row format delimited fields terminated by ',';

select * from   cookie1_sum;

 一、sum

select cookieid,
       createtime,
       pv,
       sum(pv) over (partition by cookieid order by createtime rows between unbounded preceding and current row ) p1,
       sum(pv) over (partition by cookieid order by createtime )                                                  p2,
       sum(pv) over (partition by cookieid )                                                                      p3,
       sum(pv) over (partition by cookieid order by createtime rows between 3 preceding and 1 following )         p4,
       sum(pv) over (partition by cookieid order by createtime rows between 3 preceding and current row )         p5,
       sum(pv) over (partition by cookieid order by createtime rows between current row and unbounded following)  p6
from cookie1_sum;

 

 说明：        

pv1--rows between unbounded preceding and current row :
 分组内从起点到当前行的pv累积，如，11号的pv1=10号的pv+11号的pv, 12号=10号+11号+12号
pv2: 分组内从起点到当前行的pv累积  同上
pv3: 分组内(cookie1)所有的pv累加
pv4 rows between 3 preceding and current row : 
分组内当前行+往前3行，如，11号=10号+11号， 12号=10号+11号+12号， 13号=10号+11号+12号+13号， 14号=11号+12号+13号+14号
pv5 rows between 3 preceding and 1 following: 
分组内当前行+往前3行+往后1行，如，14号=11号+12号+13号+14号+15号=5+7+3+2+4=21
pv6 rows between current row and unbounded following:
 分组内当前行+往后所有行，如，13号=13号+14号+15号+16号=3+2+4+4=13，14号=14号+15号+16号=2+4+4=10

如果不指定ROWS BETWEEN,默认为从起点到当前行;如果不指定ORDER BY，则将分组内所有值累加;关键是理解ROWS BETWEEN含义,也叫做WINDOW子句：
PRECEDING：往前
FOLLOWING：往后
CURRENT ROW：当前行
UNBOUNDED：起点，　

UNBOUNDED PRECEDING 表示从前面的起点，

UNBOUNDED FOLLOWING：表示到后面的终点

–其他AVG，MIN，MAX，和SUM用法一样。

二、avg

set mapreduce.map.memory.mb=8192;
set mapreduce.reduce.memory.mb=8192;
select
   cookieid,
   createtime,
   pv,
   avg(pv) over (partition by cookieid order by createtime rows between unbounded preceding and current row) as pv1, -- 默认为从起点到当前行
   avg(pv) over (partition by cookieid order by createtime) as pv2, --从起点到当前行，结果同pv1
   avg(pv) over (partition by cookieid) as pv3, --分组内所有行
   avg(pv) over (partition by cookieid order by createtime rows between 3 preceding and current row) as pv4, --当前行+往前3行
   avg(pv) over (partition by cookieid order by createtime rows between 3 preceding and 1 following) as pv5, --当前行+往前3行+往后1行
   avg(pv) over (partition by cookieid order by createtime rows between current row and unbounded following) as pv6  --当前行+往后所有行
 from hive_zb_serv_hq.cookie1_sum;

  三、max

set mapreduce.map.memory.mb=8192;
set mapreduce.reduce.memory.mb=8192;
select
   cookieid,
   createtime,
   pv,
   max(pv) over (partition by cookieid order by createtime rows between unbounded preceding and current row) as pv1, -- 默认为从起点到当前行
   max(pv) over (partition by cookieid order by createtime) as pv2, --从起点到当前行，结果同pv1
   max(pv) over (partition by cookieid) as pv3, --分组内所有行
   max(pv) over (partition by cookieid order by createtime rows between 3 preceding and current row) as pv4, --当前行+往前3行
   max(pv) over (partition by cookieid order by createtime rows between 3 preceding and 1 following) as pv5, --当前行+往前3行+往后1行
   max(pv) over (partition by cookieid order by createtime rows between current row and unbounded following) as pv6  --当前行+往后所有行
 from cookie1_sum;

  四、min

set mapreduce.map.memory.mb=8192;
set mapreduce.reduce.memory.mb=8192;
select
   cookieid,
   createtime,
   pv,
   min(pv) over (partition by cookieid order by createtime rows between unbounded preceding and current row) as pv1, -- 默认为从起点到当前行
   min(pv) over (partition by cookieid order by createtime) as pv2, --从起点到当前行，结果同pv1
   min(pv) over (partition by cookieid) as pv3, --分组内所有行
   min(pv) over (partition by cookieid order by createtime rows between 3 preceding and current row) as pv4, --当前行+往前3行
   min(pv) over (partition by cookieid order by createtime rows between 3 preceding and 1 following) as pv5, --当前行+往前3行+往后1行
   min(pv) over (partition by cookieid order by createtime rows between current row and unbounded following) as pv6  --当前行+往后所有行
 from cookie1_sum;