sum over partition by 的用法

--用法详解

0、select * from wmg_test;     ---测试数据

1、select v1,v2,sum(v2) over(order by v2) as sum     --按照 v2排序，累计n+n-1+....+1

from wmg_test;

2、select v1,v2,sum(v2) over(partition by v1 order by v2) as sum     --先分组，组内在进行 1 中的操作

from wmg_test;

3、select v1,v2,sum(v2) over(partition by v1 order by v1) as sum   ---稳定排序

from wmg_test;

4、select v1,v2,sum(v2) over(partition by v1) as sum    --相同key的进行回填处理

from wmg_test;

5、select distinct v1,sum_01                                        --取一条

from (

select v1,sum(v2) over(partition by v1) as sum_01

from wmg_test

) a;

6、当然也可以逆序累加，只需order by desc 即可

总结区别：group by 和partition by的区别

group 单纯分组

partition 也能分组，但还具备累计的功能