ROWNUM 應用案例 實現乙個拉鍊表

有以下資料表：事件標識表未這**票進入(1)或者移除(2)某**票池。我們需要對資料進行去重，就是連續多次的進入，或者連續多次的移除，都只取第一次的日期。

如圖中，黃色的記錄是不需要的。(這個表命名為demo)

首先第一步

select

scode,poolid,effective_day,adjustmode
,row_number() 
over (partition by scode,poolid,adjustmode order
by effective_day) as
rn         ,row_number() 
over (partition by scode,poolid order
by effective_day) as
rn2  
from  demo t

觀察資料的規律，然後我們用rn2-rn1。再按scode+poolid+adjustmode分組中，按日期進行排序。

然後發現rn3=1的就是我們需要的記錄.

完整的**如下：

with demo as (

select '00001' as scode,1 poolid,date'2010-01-01' as effective_day,1 as adjustmode from dual
union all
select '00001' as scode,1 poolid,date'2010-01-03' as effective_day,1 as adjustmode from dual
union all
select '00001' as scode,1 poolid,date'2010-01-05' as effective_day,2 as adjustmode from dual
union all
select '00001' as scode,1 poolid,date'2010-01-07' as effective_day,2 as adjustmode from dual
union all
select '00001' as scode,1 poolid,date'2010-02-01' as effective_day,1 as adjustmode from dual
union all
select '00001' as scode,1 poolid,date'2010-02-03' as effective_day,1 as adjustmode from dual
union all
select '00001' as scode,1 poolid,date'2010-02-07' as effective_day,2 as adjustmode from dual
union all
select '00002' as scode,1 poolid,date'2010-01-01' as effective_day,1 as adjustmode from dual
union all
select '00002' as scode,1 poolid,date'2010-01-05' as effective_day,2 as adjustmode from dual
union all
select '00002' as scode,1 poolid,date'2010-01-07' as effective_day,2 as adjustmode from dual
union all
select '00002' as scode,1 poolid,date'2010-02-01' as effective_day,1 as adjustmode from dual
union all
select '00002' as scode,1 poolid,date'2010-02-03' as effective_day,1 as adjustmode from dual
union all
select '00002' as scode,1 poolid,date'2010-02-07' as effective_day,2 as adjustmode from dual
)  ,data as (
select x.*,rn2-rn,row_number() over (partition by scode,poolid,adjustmode,rn2-rn order by rn) as rn3
from (      
select scode,poolid,effective_day,adjustmode
,row_number() over (partition by scode,poolid,adjustmode order by effective_day) as rn
,row_number() over (partition by scode,poolid order by effective_day) as rn2
from  demo t 
) x)
select * from data where rn3=1
order by 1,2,3

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