Question

我使用子查询返回折扣大于15％的所有订单的货币值。列出最后一个具有最高值

的orderid和订单值

这是我输入的内容：

SELECT SUM(od.orderid) As OrderID,
AS [Order Values]
FROM [Order Details] od
WHERE od.Discount =
    (SELECTod.Discount
    FROM [Order Details] od
    GROUP BY od.discount
    HAVING od.discount >.15)
GROUP BY od.quantity, od.discount, od.UnitPrice
ORDER BY [Order Values] ASC;

这是我得到的：

Msg 512，Level 16，State 1，Line 1 子查询返回的值超过1。子查询遵循=，！=，＆lt;，＆lt; =，＆gt;，＆gt;时不允许这样做。 =＆GT;或者当子查询用作表达式时。

我错过了什么？

Answer 1

错误在WHERE子句中。您使用=表示多个值，但该运算符仅允许1个值。所以改变这个：

WHERE od.Discount =
    (SELECT od.Discount
    FROM [Order Details] od
    GROUP BY od.discount
    HAVING od.discount >.15)

对此：

WHERE od.Discount IN
    (SELECT od.Discount
    FROM [Order Details] od
    GROUP BY od.discount
    HAVING od.discount >.15)

或者这个：

WHERE od.Discount =
    (SELECT TOP 1 od.Discount
    FROM [Order Details] od
    GROUP BY od.discount
    HAVING od.discount >.15
    ORDER BY od.Discount DESC)

Answer 2

使用WHERE IN代替WHERE = 这应该处理子查询返回的多个值

SELECT SUM(od.orderid) As OrderID,
AS [Order Values]
FROM [Order Details] od
WHERE od.Discount IN
    (SELECT od.Discount
    FROM [Order Details] od
    GROUP BY od.discount
    HAVING od.discount >.15)
GROUP BY od.quantity, od.discount, od.UnitPrice
ORDER BY [Order Values] ASC;

Answer 3

无论如何，你真的不需要子查询

 SELECT OrderID, SUM(UnitPrice * Quantity) OrderTotal
 FROM dbo.[Order Details]
 WHERE Discount > 0.15
 GROUP BY OrderID
 ORDER BY OrderTotal DESC

使用子查询

 SELECT OrderID, SUM(UnitPrice * Quantity) OrderTotal
 FROM dbo.[Order Details]
 WHERE OrderID IN (SELECT OrderID 
                   FROM dbo.[Order Details]
                   WHERE Discount > 0.15)
 GROUP BY OrderID
 ORDER BY OrderTotal DESC

使用EXISTS运算符

 SELECT OD.OrderID, SUM(OD.UnitPrice * OD.Quantity) OrderTotal
 FROM dbo.[Order Details] OD
 WHERE EXISTS (SELECT 1
               FROM dbo.[Order Details]
               WHERE OrderID = OD.OrderID
               AND Discount > 0.15)
 GROUP BY OD.OrderID
 ORDER BY OrderTotal DESC

无法弄清楚我错过了什么？

3 个答案: