使用相关的子查询和最大

Question

inventoryPart

：

-partnumber

，partDescription，cattoryId，eoq，stickprice， 重新级，Stocklevel，Stockonorder，重量

和

custorderline

订单，partnumber，UnitPrice，OrderQuantity，折扣，状态

我只需要返回最昂贵的库存部分的partnumber，partDeScription，股票和类别。 到目前为止，这是我提出的最好的...

SELECT IP.PartNumber, IP.PartDescription, IP.CategoryID, IP.StockPrice
FROM InventoryPart IP, CustOrderLine COL
WHERE IP.PartNumber = COL.PartNumber
AND COL.UnitPrice IN
  (SELECT MAX(COL.UnitPrice)
   FROM CustOrderLine COL)

此代码的问题是它返回所有类别的最大单位率，而不是按类别分开 我陷入了这个问题，我非常感谢您的帮助。

这样的事情应该使用子查询来使您的

MAX

UITPRICE与每个类别相关联。

SELECT DISTINCT IP.*
FROM InventoryPart IP
   JOIN CustOrderLine COL ON IP.PartNumber = COL.PartNumber
   JOIN (
    SELECT IP.CategoryID, MAX(COL.UnitPrice) MaxPrice
    FROM InventoryPart IP INNER JOIN
        CustOrderLine COL ON IP.PartNumber = COL.PartNumber
    GROUP BY IP.CategoryID
   ) T ON IP.CategoryId = T.CategoryId AND COL.UnitPrice = T.MaxPrice

the是一个减少的

fiddle

，显示了每类单价最高的库存零件。

Answer 1

SELECT  a.PartNumber, a.PartDescription, a.CategoryID, a.StockPrice
FROM    InventoryPart a
        INNER JOIN
        (
            SELECT  PartNumber, MAX(StockPrice) max_price
            FROM    Inventorypart
            GROUP   BY PartNumber
        ) b ON  a.partNumber = b.PartNumber AND
                a.StockPrice = b.max_price

为了更好的性能，请在列上添加一个

INDEX

(PartNumber, StockPrice)

update1

Answer 2

和

SELECT  a.PartNumber, a.PartDescription, a.CategoryID, a.StockPrice
FROM    InventoryPart a
        INNER JOIN
        (
            SELECT  PartNumber, CategoryID, MAX(StockPrice) max_price
            FROM    Inventorypart
            GROUP   BY PartNumber, CategoryID
        ) b ON  a.partNumber = b.PartNumber AND
                a.StockPrice = b.max_price AND
                a.CategoryID = b.CategoryID