SQL 查询的输出不足

Question

我正在使用 northwind 数据库：http://dev.assets.neo4j.com.s3.amazonaws.com/wp-content/uploads/Northwind_diagram.jpg

我必须输出所有由 CustomerID ALFKI 下达的包含多个独特产品的订单。我得到了正确的订单，但我不明白为什么每个订单只打印一个产品名称。

我的查询：

SELECT a.OrderID, p.ProductName
FROM Products p 
INNER JOIN 'Order Details' a 
  ON (p.ProductID = a.ProductID) 
INNER JOIN Orders b 
  ON (a.OrderID = b.OrderID) 
WHERE (b.CustomerID = 'ALFKI') 
GROUP BY a.OrderID 
HAVING COUNT(DISTINCT a.ProductID) > 1

Answer 1

您需要 GROUP BY 和 HAVING 成为子查询的一部分，您的主查询使用从子查询返回的 OrderID 列表作为筛选条件来选择详细信息.为 T-SQL 尝试以下语法：

SELECT 
    a.OrderID, 
    p.ProductName
FROM 
    Products p 
    INNER JOIN [Order Details] a 
        ON (p.ProductID = a.ProductID) 
    INNER JOIN Orders b 
        ON (a.OrderID = b.OrderID) 
WHERE 
    a.OrderID IN 
    (
        SELECT a.OrderID
        FROM [Order Details] a 
        INNER JOIN Orders b 
            ON (a.OrderID = b.OrderID) 
        WHERE (b.CustomerID = 'ALFKI') 
        GROUP BY a.OrderID 
        HAVING  COUNT(DISTINCT a.ProductID) > 1
    )

SQL 查询的输出不足

Insufficient output from SQL query

sql

output

northwind