-- 这个sql注释够清晰了吧-_-||
-- mysql为例
-- A字段类型:yyyy-MM-dd
select
D
,A
,B
,C
,sum(C) over (PARTITION by D,substring(A,7) order by A asc ) as SUM_C -- 某月逐层累计C
,sum(B) over (PARTITION by D,substring(A,7) order by A asc ) as SUM_B -- 某月逐层累计B
,sum(B)/sum(C) over (PARTITION by D,substring(A,7) order by A asc ) as AVG_result -- 这个结果(某月逐层平均值)
from tmp
where substring(A,7) = "2020-06" -- 限制(某月)2020年6月份数据