SQL为每个部门选择最大销售额的日期[重复]

Posted 2023-02-16

【中文标题】SQL为每个部门选择最大销售额的日期[重复]

【英文标题】：SQL Selecting dates with maximum sale for each department [duplicate]

【发布时间】：2020-03-06 21:52:36

【问题描述】：

我为编写一个棘手的查询而烦恼。

我有下表：

每个部门我想打印利润最大的日期；

我尝试自己提出这样的查询：

Select DISTINCT(Name), Date_sale, MAX(A) as B FROM (SELECT 
 Departments.Name, SALES.Date_sale, SUM(GOODS.Price * SALES.Quantity) 
 AS A FROM DEPARTMENTS, GOODS, SALES
 WHERE DEPARTMENTS.Dept_id = GOODS.Dept_id AND GOODS.Good_id = 
 SALES.Good_id GROUP BY DEPARTMENTs.Name, SALES.Date_sale) 
 GROUP BY Name, Date_sale;

但问题是部门被打印多次，因为我按名称和日期分组。

我应该如何解决它？

【参考方案1】：

你可以试试下面的方法-

with cte as 
(
 SELECT 
 Departments.Name, SALES.Date_sale, SUM(GOODS.Price * SALES.Quantity) 
 AS profit FROM DEPARTMENTS inner join GOODS on DEPARTMENTS.Dept_id = GOODS.Dept_id
 inner join SALES on GOODS.Good_id = SALES.Good_id
 GROUP BY DEPARTMENTs.Name, SALES.Date_sale
)A

select * from cte a
where profit =
     (select max(profit) from cte b on a.department=b.department)

或者你可以使用row_number()

select * from
(
select *, row_number() over(partition by department oder by profit desc) as rn
from cte
)A where rn=1

【参考方案2】：

我会在这里使用 join-s，因为它需要从通过第三个表链接的 2 个表中提取信息。

类似这样的东西（但我没有测试过这个查询，只是提出一种方法）：

Select department.name as dept, MAX(sales.quantity) as max_sales, sales.date_sale 
  from goods
Left outer join departments on departments.dept_id = goods.dept_id
Left outer join sales on sales.good_id = goods.good_id
Group by dept

【讨论】：

这在GROUP BY 子句和聚合函数中都不能作为date_sale 工作。

【参考方案3】：

您可以使用ROW_NUMBER 编写它，这将为按部门分组的每个日期的总计数提供一个数字，然后您可以使用rn = 1 获取最高销售日期

SELECT NAME, DATE_SALE, A
FROM
    (
        SELECT
            DEPARTMENTS.NAME, SALES.DATE_SALE,
            ROW_NUMBER() OVER(
                PARTITION BY DEPARTMENTS.NAME
                ORDER BY SUM(GOODS.PRICE * SALES.QUANTITY) DESC NULLS LAST
            ) AS RN,
            SUM(GOODS.PRICE * SALES.QUANTITY) AS A
        FROM DEPARTMENTS
            JOIN GOODS ON ( DEPARTMENTS.DEPT_ID = GOODS.DEPT_ID )
            JOIN SALES ON ( GOODS.GOOD_ID = SALES.GOOD_ID )
        GROUP BY DEPARTMENTS.NAME,
            SALES.DATE_SALE
    )
WHERE RN = 1;

重要，使用标准的 ANSI 连接。

干杯！！