MySQL - SUM() OVER() 函数用法详解

Posted 2021-06-16 Lux_Sun

• 测试数据

select * from wmg_test;

 

• 按照 v2 排序，累计 n+n-1+....+1

select v1,v2,sum(v2) over(order by v2) as sum
from wmg_test;

 

• 先分组，组内在进行上一个案例中的操作

select v1,v2,sum(v2) over(partition by v1 order by v2) as sum
from wmg_test;

 

• 稳定排序

select v1,v2,sum(v2) over(partition by v1 order by v1) as sum
from wmg_test;

 

• 相同 key 的进行回填处理

select v1,v2,sum(v2) over(partition by v1) as sum
from wmg_test;

 

• 取一条

select distinct v1,sum_01                             
from (
    select v1,sum(v2) over(partition by v1) as sum_01
    from wmg_test
) a;

• 当然也可以逆序累加，只需 order by desc 即可

 

总结（group by & partition by）

• group 单纯分组
• partition 也能分组，但还具备累计的功能