unbounded preceding 起始行
unbounded following 结尾行
current row 当前行
1 preceding 当前行的前1行
1 following 当前行的后1行

首先这是数据格式

1.当前行到最后一行的汇总（逐行递减）

with tt as(

select a.*,sum(mainid)over(rows between current row and unbounded following) as sums
from (
select recid,buyerid,mainid 
from bi_edw.edw_crm_jd_sales_tmp
order by recid 
limit 4
)a
)
select * from tt

结果：

2.第一行跟当前行的汇总（累加࿰