如何根据与该 groupby SUM 的 AVERAGE 进行比较的 groupby SUM 进行选择

Posted 2023-02-16

【中文标题】如何根据与该 groupby SUM 的 AVERAGE 进行比较的 groupby SUM 进行选择

【英文标题】：How to SELECT based on grouped SUM that is compared to the AVG of that grouped SUM

【发布时间】：2021-03-12 08:34:09

【问题描述】：

我有一张包含电影、类别和价格的表格。 现在我只想选择总价格（该类别下每部电影的所有价格总和）高于这些类别总价格平均值的类别。 我已经能够找到总价格的平均值（感谢这个网站），但无法将它们组合在一起。 以下是查询：

-- Return the average sums of the price per category
SELECT AVG(sum_price)
FROM 
(
SELECT category, sum(price) AS sum_price
FROM film_list
GROUP BY category
) AS inner_query;

-- Return category and its total price
SELECT category, SUM(price)
FROM film_list
GROUP BY category;

--[Error] Return only the category with sums of price larger than the average of sum of prices
SELECT category, SUM(price)
FROM film_list
WHERE SUM(price) >
(
   SELECT AVG(sum_price)
   FROM 
   (
       SELECT category, sum(price) AS sum_price
       FROM film_list
       GROUP BY category
   ) AS inner_query
);

任何帮助将不胜感激，谢谢！

【问题讨论】：

请提供样本数据和期望的结果。

可能您想使用HAVING 子句。 dev.mysql.com/doc/refman/5.6/en/group-by-handling.html

【参考方案1】：

使用窗口函数最容易解决这个问题：

SELECT c.*
FROM (SELECT category, SUM(price) AS sum_price,
             AVG(SUM(price)) OVER () as avg_total_price
      FROM film_list
      GROUP BY category
     ) c
WHERE sum_price > avg_total_price

【讨论】：

它有效！刚刚查找了 OVER 子句，现在我知道了窗口函数。谢谢！

【参考方案2】：

尝试添加group by，然后使用having

SELECT category, SUM(price)
FROM film_list
GROUP BY category
HAVING SUM(price) >
(
   SELECT AVG(sum_price)
   FROM 
   (
       SELECT category, sum(price) AS sum_price
       FROM film_list
       GROUP BY category
   ) AS inner_query
);