当满足多个条件时，如何将它们分组以计算平均值

Question

我正在使用 Oracle 数据库，想计算不同地区的平均产品价格。

例子：

prod,amt,price
X,100,1
X,180,2
X,250,3
Y,90,2
Y,170,3
Y,280,3

这里产品 X 在一个地区的售价为 100，在另一个地区售价为 180..等等。

现在，对于某些分析，它们被分组为重叠的不同范围，我需要根据范围计算价格的平均值

需要的输出是

prod,rang(Amt),mean(price),
X,[0-200],1.5,
X,[150-300],2.5,
Y,[0-200],2.5,
Y,[150-300],3,

请注意，范围有很多，为了清楚起见，我只给出了 2 个。

我尝试如下，但 case 匹配第一个条件，并且只为 [0-200] 的 X 提供一个值，我需要 2 条记录

select prod, amt, price, 
case 
when amt between 0 and 200 then amt
when amt between 150 and 300 then amt
end as rng
from tablea

如何在 case 语句中获取 2 条匹配记录？

Answer 1

使用单个条件进行两个查询并将它们合并。这不是一个完美的解决方案，但会起作用。

SELECT prod, '0-200' rang, AVG( price )
FROM   table_name
WHERE  amt BETWEEN 0 AND 200
GROUP BY prod
UNION ALL
SELECT prod, '150-300' rang, AVG( price )
FROM   table_name
WHERE  amt BETWEEN 150 AND 300
GROUP BY prod

Answer 2

您可以使用conditional aggregation，然后使用unpivot

   select prod_a as "Prod",
          prod as "Range of Amounts",
          value as "Mean Price"
     from  
            (
            with tablea(prod,amt,price) as
            (
              select 'X',100,1 from dual union all
              select 'X',180,2 from dual union all
              select 'X',250,3 from dual union all
              select 'Y',90, 2 from dual union all
              select 'Y',170,3 from dual union all
              select 'Y',280,3 from dual 
            )
            select prod as prod_a,  
            avg(case when amt between 0 and 200 then price end) as avg_0_200,
            avg(case when amt between 150 and 300 then price end) as avg_150_300
            from tablea a
            group by prod
             ) b  
    unpivot(value for prod in(avg_0_200,avg_150_300))
    order by prod_a;

   Prod  Range of Amounts   Mean Price
   ----  ----------------    ----------
   X     AVG_0_200              1.5
   X     AVG_150_300            2.5
   Y     AVG_0_200              2.5
   Y     AVG_150_300            3

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