Hive多维分析函数——With cube、Grouping sets、With rollup

有些指标涉及【多维度】的聚合，大的汇总维度，小的明细维度，需要精细化的下钻。

grouping sets： 多维度组合，组合维度自定义；
with cube： 多维度组合，程序自由组合，组合为各个维度的笛卡尔积；
**with rollup：**是 with cube的子集，以左侧维度为主，即不允许左侧为NULL，右侧为非NULL的情况出现

一、grouping sets

0 数据准备

sql 复制代码

with test1 as
     (select '2021-08' as month_date,'2021-08-11' as day_date,10 as pv
      union all
      select '2021-08' as month_date,'2021-08-10' as day_date,15 as pv
      union all
      select '2021-08' as month_date,'2021-08-08' as day_date,35 as pv
      union all
      select '2021-07' as month_date,'2021-07-08' as day_date,35 as pv
      union all
      select '2021-07' as month_date,'2021-07-06' as day_date,25 as pv
      union all
      select '2021-07' as month_date,'2021-07-03' as day_date,15 as pv)
      select 
        month_date,
        day_date,
        sum(pv) as pv
     from test1
      group by month_date,day_date
      grouping sets
       (
          (),
          (month_date),
          (month_date,day_date),
          (day_date)
        )
      order by month_date,day_date;

1 结果分析

二、with cube

0 数据准备

sql 复制代码

with test1 as
(select '2021-08' as month_date,'2021-08-11' as day_date,10 as pv
 union all
 select '2021-08' as month_date,'2021-08-10' as day_date,15 as pv
 union all
 select '2021-08' as month_date,'2021-08-08' as day_date,35 as pv
 union all
 select '2021-07' as month_date,'2021-07-08' as day_date,35 as pv
 union all
 select '2021-07' as month_date,'2021-07-06' as day_date,25 as pv
 union all
 select '2021-07' as month_date,'2021-07-03' as day_date,15 as pv)
 
 select 
   month_date,
   day_date,
   sum(pv) as pv
 from test1
 group by month_date,day_date
 with cube
 order by month_date,day_date;

1 结果分析

2 总结

从with cube和grouping sets的案例可以看出，两个结果是一样的；
with cube的维度组合（各个维度的笛卡尔积）就是groupingsets里面手动添加的维度，即为month_date,day_date两个维度的笛卡尔积。维度组合即为：()、 (month_date)、 (month_date,day_date)、 (day_date)

三、 with rollup

0 数据准备

sql 复制代码

with test1 as
(select '2021-08' as month_date,'2021-08-11' as day_date,10 as pv
 union all
 select '2021-08' as month_date,'2021-08-10' as day_date,15 as pv
 union all
 select '2021-08' as month_date,'2021-08-08' as day_date,35 as pv
 union all
 select '2021-07' as month_date,'2021-07-08' as day_date,35 as pv
 union all
 select '2021-07' as month_date,'2021-07-06' as day_date,25 as pv
 union all
 select '2021-07' as month_date,'2021-07-03' as day_date,15 as pv)

select 
  month_date,
  day_date,
  sum(pv) as pv
from test1
group by month_date,day_date
with rollup
order by month_date,day_date;

1 结果分析

2 总结

从结果上可以看出，with rollup 和with cube的区别是，少了day_date这个单独维度的聚合，因为with rollup是以左侧维度为主，当左侧month_date维度为NULL时，右侧day_date维度必须为NULL。

参考文章：

https://zhuanlan.zhihu.com/p/631268351

https://blog.51cto.com/u_14555/6696007