Hive分析窗体函数之SUM，AVG，MIN和MAX

Hive中提供了非常多的分析函数，用于完毕负责的统计分析。

本文先介绍SUM、AVG、MIN、MAX这四个函数。

环境信息：

Hive版本号为apache-hive-0.14.0-bin

Hadoop版本号为hadoop-2.6.0

Tez版本号为tez-0.7.0

构造数据：

P088888888888,2016-02-10,1

P088888888888,2016-02-11,3

P088888888888,2016-02-12,1

P088888888888,2016-02-13,9

P088888888888,2016-02-14,3

P088888888888,2016-02-15,12

P088888888888,2016-02-16,3

创建表：

hive (hiveinaction)> create table windows_func

                   >(

                  >     polno string,

                  >     createtime string,

                  >     pnum int   

                   >)

                   >ROW FORMAT DELIMITED

                   >FIELDS TERMINATED BY ‘,‘

                   >stored as textfile;

导入数据到表中：

load data local inpath ‘/home/hadoop/testhivedata/windows_func.txt‘ into table windows_func;

測试：

SELECT polno,

       createtime,

       pnum,

       SUM(pnum) OVER(PARTITION BY polno ORDERBY createtime) AS pnum1, --默觉得从起点到当前行

       SUM(pnum) OVER(PARTITION BY polno ORDERBY createtime ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS pnum2,  --从起点到当前行

       SUM(pnum) OVER(PARTITION BY polno) ASpnum3, --分组内全部行

       SUM(pnum) OVER(PARTITION BY polno ORDERBY createtime ROWS BETWEEN 3 PRECEDING AND CURRENT ROW) AS pnum4,  --当前行+往前3行(当前行的值+前面三行的值)

       SUM(pnum) OVER(PARTITION BY polno ORDERBY createtime ROWS BETWEEN 3 PRECEDING AND 1 FOLLOWING) AS pnum5,  --当前行+往前3行+往后1行

       SUM(pnum) OVER(PARTITION BY polno ORDERBY createtime ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) AS pnum6 ---当前行+往后全部行

FROM windows_func;

结果：

凝视：

1.   假设不指定ROWS BETWEEN,默觉得从起点到当前行;

2.   假设不指定ORDER BY，则将分组内全部值累加;

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
其它AVG，MIN。MAX。和SUM使用方法一样。

演示AVG环境：

SELECT polno,

       createtime,

       pnum,

       AVG(pnum) OVER(PARTITION BY polno ORDER BY createtime) AS pnum1, --默觉得从起点到当前行

       AVG(pnum) OVER(PARTITION BY polno ORDER BY createtime ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS pnum2,  --从起点到当前行

       AVG(pnum) OVER(PARTITION BY polno) AS pnum3, --分组内全部行

       AVG(pnum) OVER(PARTITION BY polno ORDER BY createtime ROWS BETWEEN 3 PRECEDING AND CURRENT ROW) AS pnum4,  --当前行+往前3行(当前行的值+前面三行的值)

       AVG(pnum) OVER(PARTITION BYpolno ORDER BY createtime ROWS BETWEEN 3 PRECEDING AND 1 FOLLOWING) AS pnum5,  --当前行+往前3行+往后1行

       AVG(pnum) OVER(PARTITION BYpolno ORDER BY createtime ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) AS pnum6 ---当前行+往后全部行

FROM windows_func;

结果：

其它相似的函数就不举例了。