使用 partition by 和 case when

Question

总结一下我正在尝试做的事情：

我有一堆区域，其中一个包含很多产品。我已经计算了每种产品的折扣，产品的平均折扣（按地区划分）以及它们的标准差（也按地区划分）。

现在，我需要计算一个新的平均折扣（再次按地区划分），但只考虑 discount

的产品

select  product,
        discount,
        region,
--this is the line i want to add
        avg (case when discont < avg_discount + stddev_discount then discount) over(partition by region) end as new_discount*
from (
  select product,
         discount,
         region,
         avg(discount) over (partition by region) as avg_discount,
         stddev(discount) over (partition by region) as stddev_discount
  from base
)

我想要什么：

Answer 1

我有点不清楚你想要什么结果。根据您的描述，聚合似乎足以获得最终结果。

无论如何，我们的想法是使用子查询或 CTE。 像这样的：

select region, avg(discount)
from (select t.*,
             avg(discount) over (partition by region) as region_avg,
             stddev(discount) over (partition by region) as region_stddev
      from t
     ) t
where discount < region_avg + region_stdev
group by region;

编辑：

您可以调整它以使用窗口功能：

select t.*,
       avg(case when discount < region_avg + region_stdev then discount end) over (region) as new_avg
from (select t.*,
             avg(discount) over (partition by region) as region_avg,
             stddev(discount) over (partition by region) as region_stddev
      from t
     ) t;