找出每个类别中最畅销的 3 种产品

Question

我正在尝试查找每个类别中最畅销的 3 种产品。但是我试过的 SQL 没有产生正确的结果。这是我所做的事情：

产品Table:

CREATE TABLE [dbo].[Products](
    [id] [int] IDENTITY(1,1) NOT NULL,
    [name] [nvarchar](100) NOT NULL,
    [category] [nvarchar](100) NOT NULL,
 CONSTRAINT [PK_Products] PRIMARY KEY CLUSTERED 
(
    [id] ASC
)

id	name	category
1	prod1	cat1
2	prod2	cat1
3	prod3	cat1
4	prod4	cat1
5	prod5	cat1
6	prod6	cat2
7	prod7	cat2
8	prod8	cat2
10	prod10	cat2

订单商品table:

CREATE TABLE [dbo].[OrderItems](
    [id] [int] IDENTITY(1,1) NOT NULL,
    [prodID] [int] NOT NULL,
    [quantity] [int] NOT NULL,
 CONSTRAINT [PK_OrderItems] PRIMARY KEY CLUSTERED 
(
    [id] ASC
)

ALTER TABLE [dbo].[OrderItems]  WITH CHECK ADD  CONSTRAINT [FK_OrderItems_Products] FOREIGN KEY([prodID])
REFERENCES [dbo].[Products] ([id])

ALTER TABLE [dbo].[OrderItems] CHECK CONSTRAINT [FK_OrderItems_Products]

id	prodID	quantity
1	1	10
2	2	6
3	2	6
4	4	3
5	3	2
6	6	10
7	7	1

SQL 我试过了：

select *
from (select p1.id, p1.category, (select sum(quantity) from OrderItems as oi where oi.prodID = p1.id) as sales
from Products as p1) as p2
where p2.sales >= (
    select distinct(sales)
    from (select p1.id, p1.category, (select sum(quantity) from OrderItems as oi where oi.prodID = p1.id) as sales
from Products as p1) as p3
    where p2.category = p3.category
    order by sales desc
    offset 2 rows fetch next 1 rows only)

预期结果：

id	category	sales
1	cat1	10
2	cat1	12
4	cat1	3
6	cat2	10
7	cat2	1

实际结果：

id	category	sales
1	cat1	10
2	cat1	12
4	cat1	3

查询有什么错误？有没有更好的方法来达到这个效果？

Answer 1

您可以加入表并聚合以获得每个产品的总销售额。
同样使用 ROW_NUMBER() window 函数根据产品的类别并按总销售额排序对每个产品进行排名和筛选：

SELECT id, category, sales
FROM (
  SELECT p.id, 
         MAX(category) category, 
         SUM(o.quantity) sales,
         ROW_NUMBER() OVER (PARTITION BY MAX(category) ORDER BY SUM(o.quantity) DESC) rn
  FROM Products p INNER JOIN OrderItems o
  ON o.prodID = p.id
  GROUP BY p.id
) t
WHERE rn <= 3
ORDER BY id;

或者，先在OrderItems聚合，然后加入：

SELECT id, category, sales
FROM (
  SELECT p.id, 
         p.category, 
         o.sales,
         ROW_NUMBER() OVER (PARTITION BY p.category ORDER BY o.sales DESC) rn
  FROM Products p 
  INNER JOIN (
    SELECT prodID, SUM(quantity) sales
    FROM OrderItems
    GROUP BY prodID
  ) o ON o.prodID = p.id
) t
WHERE rn <= 3
ORDER BY id;

参见demo。

找出每个类别中最畅销的 3 种产品

Finding the 3 top selling products in each category

sql

sql-server

group-by

sum

window-functions