如何在Oracle SQL中使用rank()函数添加一个移动窗口

Question

我需要在移动时间窗口内对值进行排名。我参考了Tony Hasler的博客文章， https://tonyhasler.wordpress.com/2012/10/24/model-clause-use-cases/#comment-5116，但是为非窗口函数添加窗口化子句（如中位数）的解决方案不适用于排名(rank())或百分比排名(percent_rank())函数，这些函数是分析型的非窗口函数。

下面是使用median()函数的工作示例：

with a as (
    select 'a' sector, trunc(sysdate) dt, 64 v from dual union all
    select 'a' sector, trunc(sysdate)-1 dt, 2 from dual union all
    select 'a' sector, trunc(sysdate)-2 dt, 4 from dual union all
    select 'a' sector, trunc(sysdate)-3 dt, 128 from dual union all
    select 'a' sector, trunc(sysdate)-4 dt, 8 from dual union all
    select 'a' sector, trunc(sysdate)-5 dt, 16 from dual union all
    select 'a' sector, trunc(sysdate)-6 dt, 32 from dual union all
    select 'a' sector, trunc(sysdate)-7 dt, 256 from dual union all
    select 'a' sector, trunc(sysdate)-8 dt, 1 v from dual union all
    select 'a' sector, trunc(sysdate)-9 dt, 512 from dual union all
    select 'b' sector, trunc(sysdate) dt, 3 from dual union all
    select 'b' sector, trunc(sysdate)-1 dt, 27 from dual union all
    select 'b' sector, trunc(sysdate)-2 dt, 9 from dual union all
    select 'b' sector, trunc(sysdate)-3 dt, 81 from dual 
)
select * from a
model
partition by (sector)
dimension by (dt)
measures (v, 0 mov_rank)
rules 
(
    mov_rank[ANY] = median(v)[dt between CV()-3 and CV()]
)
order by sector, dt
;

如果我们将中位数替换为rank()，则示例将无法正常工作，例如：

with a as (
    select 'a' sector, trunc(sysdate) dt, 64 v from dual union all
    select 'a' sector, trunc(sysdate)-1 dt, 2 from dual union all
    select 'a' sector, trunc(sysdate)-2 dt, 4 from dual union all
    select 'a' sector, trunc(sysdate)-3 dt, 128 from dual union all
    select 'a' sector, trunc(sysdate)-4 dt, 8 from dual union all
    select 'a' sector, trunc(sysdate)-5 dt, 16 from dual union all
    select 'a' sector, trunc(sysdate)-6 dt, 32 from dual union all
    select 'a' sector, trunc(sysdate)-7 dt, 256 from dual union all
    select 'a' sector, trunc(sysdate)-8 dt, 1 v from dual union all
    select 'a' sector, trunc(sysdate)-9 dt, 512 from dual union all
    select 'b' sector, trunc(sysdate) dt, 3 from dual union all
    select 'b' sector, trunc(sysdate)-1 dt, 27 from dual union all
    select 'b' sector, trunc(sysdate)-2 dt, 9 from dual union all
    select 'b' sector, trunc(sysdate)-3 dt, 81 from dual 
)
select * from a
model
partition by (sector)
dimension by (dt)
measures (v, 0 mov_rank)
rules 
(
    mov_rank[ANY] = rank() over (order by v)[dt between CV()-3 and CV()]
)
order by sector, dt
;

我很感激您的帮助。

谢谢。

- rpm

Answer 1

这可能有点“老派”，但您可以使用自连接而不是分析或 model 来实现等效结果，例如：

with a as (
    select 'a' sector, trunc(sysdate) dt, 64 v from dual union all
    select 'a' sector, trunc(sysdate)-1 dt, 2 from dual union all
    select 'a' sector, trunc(sysdate)-2 dt, 4 from dual union all
    select 'a' sector, trunc(sysdate)-3 dt, 128 from dual union all
    select 'a' sector, trunc(sysdate)-4 dt, 8 from dual union all
    select 'a' sector, trunc(sysdate)-5 dt, 16 from dual union all
    select 'a' sector, trunc(sysdate)-6 dt, 32 from dual union all
    select 'a' sector, trunc(sysdate)-7 dt, 256 from dual union all
    select 'a' sector, trunc(sysdate)-8 dt, 1 v from dual union all
    select 'a' sector, trunc(sysdate)-9 dt, 512 from dual union all
    select 'b' sector, trunc(sysdate) dt, 3 from dual union all
    select 'b' sector, trunc(sysdate)-1 dt, 27 from dual union all
    select 'b' sector, trunc(sysdate)-2 dt, 9 from dual union all
    select 'b' sector, trunc(sysdate)-3 dt, 81 from dual 
)
select
    a.sector, 
    a.dt, 
    a.v, 
    count(case when self.v < a.v then self.v end) + 1 mov_rank
from
    a,
    a self
where
    self.sector = a.sector
    and
    self.dt between a.dt - 3 and a.dt + 3
group by 
    a.sector, 
    a.dt, 
    a.v
order by 
    a.sector, 
    a.dt, 
    a.v;

- Brian Camire