查找按类别分组的不同列的总和的最大值

Question

这是我的数据集

我想找出每个国家/地区最受欢迎的产品。

我已经尝试过了

SELECT
    "Country", 
    MAX(Ft, Vg, Mt),
    SUM("Fruit") AS Ft,
    SUM("Veg") AS Vg,
    SUM("Meat") AS Mt,
FROM
    "My_Data_Set"
GROUP BY
    ("Country");

还有很多其他事情，但无法让任何东西发挥作用。

Answer 1

架构（MySQL v8.0）

CREATE TABLE customers (
    CustomerId SERIAL PRIMARY KEY,
    Country VARCHAR(255),
    Fruit INTEGER,
    Veg INTEGER,
    Meat INTEGER
);

INSERT INTO customers (CustomerId, Country, Fruit, Veg, Meat) VALUES
(1, 'Spain', 100, 25, 60),
(2, 'USA', 20, 50, 150),
(3, 'India', 25, 20, 15),
(4, 'Germany', 35, 46, 75),
(5, 'Spain', 22, 36, 50),
(6, 'USA', 12, 34, 56),
(7, 'India', 67, 22, 38),
(8, 'Germany', 21, 45, 18);

---

查询

with cus as (
  select 
    distinct country, 
    sum(fruit) over(partition by country) as fruit, 
    sum(veg) over (partition by country) as veg, 
    sum(meat) over (partition by country) as meat 
  from 
    customers
) 
select 
  country, 
  case when fruit > veg 
  AND fruit > meat THEN 'fruit' WHEN veg > fruit 
  AND veg > meat THEN 'veg' WHEN meat > fruit 
  AND meat > veg THEN 'meat' end as popular_product 
from 
  cus;

国家	热门产品
德国	肉
印度	水果
西班牙	水果
美国	肉

---

在 DB Fiddle 上查看