Question

我有以下查询：

SELECT 
    ShipperName, S.ShipmentID, DepartureDate
FROM 
    SHIPMENT S, SHIPMENT_ITEM SI
WHERE 
    S.ShipmentID = SI.ShipmentID
    AND Value > 1000
ORDER BY 
    ShipperName ASC, DepartureDate DESC;

返回以下结果：

International                       4   2013-06-02
International                       4   2013-06-02
International                       4   2013-06-02
Worldwide                           3   2013-05-05

前三个结果相同，但我要找的是：

International                       4   2013-06-02
Worldwide                           3   2013-05-05

我做错了什么？

Answer 1

您可能需要在select语句中添加DISTINCT关键字。

像：

SELECT DISTINCT ShipperName, S.ShipmentID, DepartureDate
FROM SHIPMENT S, SHIPMENT_ITEM SI
WHERE S.ShipmentID = SI.ShipmentID
AND Value > 1000
ORDER BY ShipperName ASC, DepartureDate DESC;

Answer 2

;WITH CTE AS
(
    SELECT ShipperName
         , S.ShipmentID
         , DepartureDate
         , ROW_NUMBER() OVER (PARTITION BY ShipperName ORDER BY ShipperName) rn
    FROM SHIPMENT S 
    INNER JOIN SHIPMENT_ITEM SI
    ON S.ShipmentID = SI.ShipmentID
    WHERE Value > 1000
    ORDER BY ShipperName ASC, DepartureDate DESC
)
SELECT ShipperName
      ,ShipmentID
      ,DepartureDate
FROM CTE 
WHERE rn = 1

Answer 3

使用EXPLICIT join，因为隐式JOIN已过时且已弃用

您似乎有多个条目与货件ID匹配，使用不同的关键字，或者您可能在某些列上缺少联接

SELECT distinct ShipperName, S.ShipmentID, DepartureDate
FROM SHIPMENT S
JOIN SHIPMENT_ITEM SI
ON S.ShipmentID = SI.ShipmentID
AND Value > 1000
ORDER BY ShipperName ASC, DepartureDate DESC;

Answer 4

您选择的数据似乎完全来自货件表（ShipperName，S.ShipmentID，DepartureDate），但您要将该表加入ShipmentItem表，每件货物显然可能有多于一排。您的联接表每个项目都有一行（与发货表中的货件相关）。

显然，您只希望货件包含至少一个value大于1000的项目，但在编写查询时，您将获得每个项目的结果行< / em>有这样的价值。实现您想要的最简单方法可能就是将DISTINCT关键字添加到您的查询中，正如其他人所建议的那样。但是，还有其他选择，其中一些可能更适合不同的，更复杂的要求。

Microsoft SQL Server复制查询结果

4 个答案: