over()
over() 函数在Hive中运用广泛，通常搭配row_number() ,min(),max(),sum()来使用,总结下over函数划定窗口的范围

• over() 因为没设置窗口范围，此时每一行的窗口都是所有的行。

SELECT 
	id,
	name,
	num,
	sum(num) over() sum1 
from 
	aa

也就是每一行后面的sum1是对所有行的num进行sum(num)操作，如果设置好窗口范围，每一行后面的结果是对以当前行为中心按照窗口范围内的行进行sum(num)操作得出结果。一下会有对应的案例

• over(order by id) id=1的窗口只有一行，id=2的窗口包括id=1,id=2

SELECT 
	id,
	name,
	num,
	sum(num) over(order by id) sum1 
from 
	aa

• over(partition by name) 每一行根据 name来区分窗口

SELECT 
	id,
	name,
	num,
	sum(num) over(partition by name) sum1 
from 
	aa

• over(partition by name order by id) 每一行根据 name来区分窗口,再根据order by 取具体的范围

SELECT 
	id,
	name,
	num,
	sum(num) over(partition by name order by id) sum1 
from 
	aa

• over( order by id range between 1 preceding and 1 following ) range 代表范围 preceding 向前 following 向后 窗口范围当前行前后一行

SELECT 
	id,
	name,
	num,
	sum(num) over( order by id range between 1 preceding and 1 following ) sum1 
from 
	aa

• over( order by id range between CURRENT ROW AND 1 following ) 窗口范围当前行和后面一行

SELECT 
	id,
	name,
	num,
	sum(num) over( order by id range between CURRENT ROW AND  1 following ) sum1 
from 
	aa