Question

我有一个场景，其中包含以下查询：

SELECT
Purchasing.Supplier,
PurchasingParts.Part,
PurchasingParts.Description,
PurchasingParts.CostPerUnit,
PurchasingParts.PurchaseOrderNum,
PurchasingParts.ItemNum
FROM PurchasingParts
INNER JOIN Purchasing ON PurchasingParts.PurchaseOrderNum = Purchasing.PurchaseOrderNum
WHERE Supplier = 'Sup1'
ORDER BY PurchasingParts.PurchaseOrderNum DESC

返回以下结果：

Supplier    Part    Description CostPerUnit PurchaseOrderNum    ItemNum
Sup1        cm-14b  NULL        9.99        37163               1
Sup1        cm-13   jkljlkjlk   9.99        37160               1
Sup1        cm-13   jkljlkjlk   NULL        37158               1

但是，我想过滤那组结果，以便只显示最近的订单（即最高的PurchaseOrderNum）PER PART（仅在Part属性上执行）。所以在这种情况下，最终结果将是：

Supplier    Part    Description CostPerUnit PurchaseOrderNum    ItemNum
Sup1        cm-14b  NULL        9.99        37163               1
Sup1        cm-13   jkljlkjlk   9.99        37160               1

我正在使用SQL Server 2008。

Answer 1

您可以使用ROW_NUMBER()：

SELECT t.* FROM (
    SELECT
        Purchasing.Supplier,
        PurchasingParts.Part,
        PurchasingParts.Description,
        PurchasingParts.CostPerUnit,
        PurchasingParts.PurchaseOrderNum,
        PurchasingParts.ItemNum,
        ROW_NUMBER() OVER(PARTITION BY PurchasingParts.Part ORDER BY PurchasingParts.PurchaseOrderNum DESC) as rnk
    FROM PurchasingParts
    INNER JOIN Purchasing ON PurchasingParts.PurchaseOrderNum = Purchasing.PurchaseOrderNum
    WHERE Supplier = 'Sup1'
    ) t
WHERE t.rnk = 1
ORDER BY t.PurchaseOrderNum DESC

SQL - 在结果集中获取每个属性的TOP值

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