oracle 先排序 在分組

類似實現: 先排序

A    1
A    1
B    2
B    3
A    4

在排序的基礎上實現分組相加

A 2
B 5
A 4

 

with tab1 as (
select 'a' id,1 val ,1 ord from dual UNION all
select 'a' id,1 val ,2 ord from dual UNION all
select 'a' id,1 val ,3 ord from dual UNION all
select 'b' id,1 val ,4 ord from dual UNION all
select 'b' id,1 val ,4 ord from dual UNION all
select 'b' id,1 val ,5 ord from dual UNION all
select 'a' id,1 val ,6 ord from dual UNION all
select 'a' id,1 val ,7 ord from dual 
),tab2 as (
select t1.*,decode(lag(t1.id) over (order by t1.ord) , t1.id ,0 ,1) lag from tab1 t1
),tab3 as (
select t1.*,sum(t1.lag) over( order by t1.ord) sm from tab2 t1
) 
-- select t1.*, decode(lag(t1.id) over (order by t1.ord) , t1.id ,0 ,1) lag from tab1 t1;
-- select t1.*,sum(t1.lag) over ( order by t1.ord) sm from tab2 t1;
select t1.id,sum(t1.val) from tab3 t1 group by t1.id,t1.sm order by t1.sm;

本文用到的oracle 函數   lag 獲取上下行分析函數  sum over 連續求和分析函數
以及一個很騷的想法，可以放開註釋 觀察中間表 tab2 的數據