Question

我有一个包含4个表的小型数据库：客户 - 订单 - OrderLine - 产品，我正在玩一些查询，并试图获取最昂贵订单的人的名字。

经过一些游戏后，我想出了以下查询，其中显示了所有订单的价格：

SELECT SUM(OrderLine.Amount * Product.Price) AS OrderLinePrice, Orders.Id, Customer.Lastname
FROM OrderLine, Product, Orders, Customer
WHERE OrderLine.ProductId = Product.Id
AND Orders.Id = OrderLine.OrderId
AND Customer.Id = Orders.CustomerId
GROUP BY Orders.Id, Customer.Lastname
ORDER BY OrderLinePrice DESC

现在我在概念上需要做的，或者我认为我需要做的是，应用MAX（）来只选择最高的OrderLinePrice，但是我没有成功，因为SQL Server抱怨无法执行聚合函数包含聚合的表达式......

===============更新：

目前我的查询如下：

SELECT t.CustomerLastName
FROM (
    SELECT SUM(OrderLine.Amount * Product.Price) AS OrderLinePrice, Orders.Id, Customer.Lastname AS CustomerLastName
    FROM OrderLine, Product, Orders, Customer
    WHERE OrderLine.ProductId = Product.Id
    AND Orders.Id = OrderLine.OrderId
    AND Customer.Id = Orders.CustomerId
    GROUP BY Orders.Id, Customer.Lastname
    ) AS t
WHERE t.OrderLinePrice = 
(
    SELECT MAX(s.OrderLinePrice) AS MaxOrderPrice
    FROM (
        SELECT SUM(OrderLine.Amount * Product.Price) AS OrderLinePrice, Orders.Id, Customer.Lastname AS CustomerLastName
        FROM OrderLine, Product, Orders, Customer
        WHERE OrderLine.ProductId = Product.Id
        AND Orders.Id = OrderLine.OrderId
        AND Customer.Id = Orders.CustomerId
        GROUP BY Orders.Id, Customer.Lastname
        ) AS s
)
ORDER BY CustomerLastName

这将检索客户列表，其订单价格等于最昂贵订单的价格。这确切地检索了我想要的东西，但感觉非常多余。

我应该如何开始提高效率（如果可能的话）？

Answer 1

您可以通过多种方式完成此操作。以下是一些建议：

<强> CTE

;WITH CTE
AS
(
    SELECT SUM(OrderLine.Amount * Product.Price) AS OrderLinePrice, 
    Orders.Id, Customer.Lastname
    FROM OrderLine, Product, Orders, Customer
    WHERE OrderLine.ProductId = Product.Id
    AND Orders.Id = OrderLine.OrderId
    AND Customer.Id = Orders.CustomerId
    GROUP BY Orders.Id, Customer.Lastname
)
SELECT
    MAX(OrderLinePrice) AS MaxorderPrice
FROM
    CTE

子查询，最大

SELECT
    MAX(t.OrderLinePrice) AS MaxorderPrice
FROM
    (
        SELECT SUM(OrderLine.Amount * Product.Price) AS OrderLinePrice, 
            Orders.Id, Customer.Lastname
        FROM OrderLine, Product, Orders, Customer
        WHERE OrderLine.ProductId = Product.Id
        AND Orders.Id = OrderLine.OrderId
        AND Customer.Id = Orders.CustomerId
        GROUP BY Orders.Id, Customer.Lastname
    ) AS t

按订单排名第一

SELECT TOP 1
    t.Amount
FROM
    (
        SELECT SUM(OrderLine.Amount * Product.Price) AS OrderLinePrice, 
            Orders.Id, Customer.Lastname
        FROM OrderLine, Product, Orders, Customer
        WHERE OrderLine.ProductId = Product.Id
        AND Orders.Id = OrderLine.OrderId
        AND Customer.Id = Orders.CustomerId
        GROUP BY Orders.Id, Customer.Lastname
    ) AS t
ORDER BY t.OrderLinePrice DESC

修改

也许是这样的：

;WITH CTE AS ( SELECT SUM(OrderLine.Amount * Product.Price) AS OrderLinePrice, Orders.Id, Customer.Lastname FROM OrderLine, Product, Orders, Customer WHERE OrderLine.ProductId = Product.Id AND Orders.Id = OrderLine.OrderId AND Customer.Id = Orders.CustomerId GROUP BY Orders.Id, Customer.Lastname ) SELECT * FROM CTE WHERE CTE.OrderLinePrice=(SELECT MAX(CTE2.OrderLinePrice) FROM CTE AS CTE2)

或者，如果您想要max by customer姓氏。你可以这样做：

;WITH CTE AS ( SELECT SUM(OrderLine.Amount * Product.Price) AS OrderLinePrice, Orders.Id, Customer.Lastname FROM OrderLine, Product, Orders, Customer WHERE OrderLine.ProductId = Product.Id AND Orders.Id = OrderLine.OrderId AND Customer.Id = Orders.CustomerId GROUP BY Orders.Id, Customer.Lastname ) SELECT MAX(OrderLinePrice) AS MaxPrice, Lastname FROM CTE GROUP BY CTE.Lastname

Answer 2

首先，您是否考虑过使用显式连接？它可能只是一个品味问题，但也许您会发现显式连接的查询比隐式连接（或“逗号”连接）更清晰，就像在您的示例中一样。

至于问题，您可以使用TOP (1) WITH TIES，如下所示：

WITH ranked AS (
  SELECT
    SUM(ol.Amount * p.Price) AS OrderLinePrice,
    o.Id,
    c.Lastname AS CustomerLastName
  FROM OrderLine ol
    INNER JOIN Product  p ON p.Id = ol.ProductId
    INNER JOIN Orders   o ON o.Id = ol.OrderId
    INNER JOIN Customer c ON c.Id = o.CustomerId
  GROUP BY Orders.Id, Customer.Lastname
)
SELECT *
FROM (
  SELECT TOP (1) WITH TIES CustomerLastName
  FROM ranked
  ORDER BY OrderLinePrice DESC
) s
ORDER BY CustomerLastName

或者您可以使用RANK()或DENSE_RANK()，如下所示：

WITH ranked AS (
  SELECT
    SUM(ol.Amount * p.Price) AS OrderLinePrice,
    o.Id,
    c.Lastname AS CustomerLastName,
    RANK() OVER (ORDER BY SUM(ol.Amount * p.Price) DESC) AS rnk
  FROM OrderLine ol
    INNER JOIN Product  p ON p.Id = ol.ProductId
    INNER JOIN Orders   o ON o.Id = ol.OrderId
    INNER JOIN Customer c ON c.Id = o.CustomerId
  GROUP BY Orders.Id, Customer.Lastname
)
SELECT CustomerLastName
FROM ranked
WHERE rnk = 1
ORDER BY CustomerLastName

如果您只对最高价格感兴趣，RANK()就足够了，但如果您希望客户获得最高 n 总计，请使用DENSE_RANK()相反，将条件从rnk = 1更改为rnk <= n。

使用最昂贵的订单获取客户的名称

2 个答案: