Question

我有一张名为'Purchases'的表：

PurchaseID，PurchaseDate，Vendor

╔════════════╦══════════════╦════════╗
║ PurchaseID ║ PurchaseDate ║ Vendor ║
╠════════════╬══════════════╬════════╣
║          1 ║ 01 jan 2013  ║ XYZ    ║
║          2 ║ 02 jan 2013  ║ ABC    ║
╚════════════╩══════════════╩════════╝

和使用PurchaseID密钥链接的表'PurchaseDetails'：

DetailID，PurchaseID，ProductCode，Price

╔══════════╦════════════╦═════════════╦═══════╗
║ DetailID ║ PurchaseID ║ ProductCode ║ Price ║
╠══════════╬════════════╬═════════════╬═══════╣
║        1 ║          1 ║         001 ║ 2.34  ║
║        2 ║          1 ║         002 ║ 3.75  ║
║        3 ║          2 ║         001 ║ 5.93  ║
║        4 ║          2 ║         002 ║ 8.14  ║
╚══════════╩════════════╩═════════════╩═══════╝

我想获得给定ProductCode的最后一个PurchaseDate的价格和供应商。

例如：如果ProductCode是'001'，那么我希望查询返回： 5.93 | ABC

我尝试过使用带有DESC ORDER BY的TOP 1 SELECT，但是我无法让JOIN部分工作。

Answer 1

使用TOP1方法，以下查询应该可以正常工作

SELECT Vendor, Price
FROM Purchases p
INNER JOIN PurchaseDetails pd on pd.PurchaseID=p.PurchaseID
WHERE PurchaseID = (SELECT TOP 1 PurchaseID FROM Purchases WHERE DetailID = DetailID ORDER BY PurchaseDate DESC)

您也可以使用Row_Number over来实现此

Answer 2

这是我的解决方案：

SELECT TOP 1 Purchases.Vendor, Purchases.PurchaseDate, PurchaseDetails.Price FROM PurchaseDetails INNER JOIN Purchases 
ON PurchaseDetails.PurchaseID=Purchases.PurchaseID WHERE PurchaseDetails.ProductCode='001' ORDER BY Purchases.PurchaseDate DESC

Answer 3

由于您使用的是SQL Server 2005+，因此可以使用窗口函数来获取结果。在这种情况下，我使用了row_number()：

select vendor, price
from
(
  select p.purchaseId, p.purchaseDate, p.vendor,
    d.productCode, d.price,
    row_number() over(partition by d.productCode order by p.purchaseDate desc) seq
  from purchases p
  inner join purchaseDetails d
    on p.purchaseId = d.purchaseId
) src
where seq = 1;

请参阅SQL Fiddle with Demo

两个链接表中的最后一个记录查询

3 个答案: