通过临时表连接 SQL Server

Question

我有一张定价规则表。我正在检索每个ProductTypeID 的最大折扣，这表明产品是哪种类型，使用此查询：

SELECT MAX(discount) as BiggestDiscount, ProductTypeID FROM dbo.SellingPriceRules
WHERE ProductTypeID is not null
GROUP by ProductTypeID
ORDER BY ProductTypeID

这很好用，但是我需要对此进行扩展，对于ProductIDs 的列表，请检索我最大的折扣。所以我需要找到每个ProductID 所属的ProductTypeID 并检查我的SellPriceRules 数据库以获取此ProductTypeID 的最大折扣。

所以，在我的Discounts 表中，我有：

ProductID, Margin

在我的Products 表中我有：

ProductID, ProductTypeID

为了获取每个产品的 ProductTypeID，我有：

select * from Discounts m
INNER JOIN Product p on p.ProductID = m.ProductID
WHERE ProductTypeID is not null

我现在正在努力将这两个查询结合在一起。我只是想获得折扣表中每种产品的最大折扣，然后从我的利润中减去。我怎样才能将这两个退休人员联合起来？

非常感谢

Answer 1

使用相关子查询

SELECT m.ProductID, m.Margin, p.ProductTypeID, 
  m.Margin - (SELECT MAX(discount) 
              FROM dbo.SellingPriceRules 
              WHERE ProductTypeID = p.ProductTypeID)
FROM Discounts m INNER JOIN Product p on p.ProductID = m.ProductID
WHERE p.ProductTypeID IS NOT NULL

@Annon 的执行计划

Answer 2

你可以试试这样的：

select *, Margin-BiggestDiscount from Discounts m
INNER JOIN Product p on p.ProductID = m.ProductID AND p.ProductTypeID is not null
inner join (
SELECT MAX(discount) as BiggestDiscount, ProductTypeID 
FROM dbo.SellingPriceRules
GROUP by ProductTypeID) as r on p.ProductTypeID = r.ProductTypeID

Answer 3

一般情况下，您可以在这种情况下使用 CTE。像这样的：

;WITH current_discounts (BiggestDiscount, ProductTypeID)
AS (
    SELECT MAX(discount) as BiggestDiscount, ProductTypeID FROM dbo.SellingPriceRules
    WHERE ProductTypeID is not null
    GROUP by ProductTypeID
    ORDER BY ProductTypeID
)

SELECT
    m.ProductID,
    m.Margin - c.BiggestDiscount
FROM Discounts m
INNER JOIN Product p ON p.ProductID = m.ProductID
INNER JOIN current_discounts c ON p.ProductTypeID = c.ProductTypeID

Answer 4

你的所有逻辑都是正确的。您只需要将一个查询嵌入另一个查询的语法。

SELECT
  p.ProductID,
  p.ProductTypeID,
  m.Margin,
  d.BiggestDiscount,
  m.Margin - d.BiggestDiscount AS AdjustedMargin
FROM Product p
INNER JOIN Discounts m ON (p.ProductID = d.ProductID)
INNER JOIN (
  SELECT
    ProductTypeID,
    MAX(discount) as BiggestDiscount
  FROM SellingPriceRules
  GROUP BY ProductTypeID
) d ON (p.ProductTypeID = d.ProductTypeID)
WHERE p.ProductID IS NOT NULL