SQL - 如何用 record-3 对每一行求和

Question

解释起来很困难，我想对每一行的最后 3 行求和。举个例子就更好了：

ID  VALUE1  RESULT I WANT
===================
1   10   10+5+20 = 35
2   5    5+20+4  = 29
3   20   20+4+50 = 74
4   4    4+50+300 = 354
5   50   50+300+10 = 360
6   300  300+10+15 = 325
7   10   NULL
8   15   NULL

我使用 Oracle SQL。谢谢

with dummy as 
(
   select 10 as value from dual union all
   select 5 from dual union all
   select 20 from dual union all
   select 4 from dual union all
   select 50 from dual union all
   select 300 from dual union all
   select 10 from dual union ALL
   select 15 from dual 
)
SELECT value, SUM(value) FROM dummy GROUP BY value

我不知道如何处理

Answer 1

您可以使用 Oracle 函数“当前行和后续 2 行之间的行” https://learnsql.com/blog/sql-window-functions-rows-clause/，如下。

with dummy as 
(
   select 1 as id, 10 as value from dual union all
   select 2 ,5 from dual union all
   select 3, 20 from dual union all
   select 4, 4 from dual union all
   select 5, 50 from dual union all
   select 6, 300 from dual union all
   select 7, 10 from dual union ALL
   select 8, 15 from dual 
)
SELECT value, value, sum(value)
  OVER (ORDER BY id ROWS BETWEEN CURRENT ROW AND 2 FOLLOWING) sum
   FROM dummy;