罗斯文（Northwind）总和定单值并用平均值检查它们

Question

我使用Northwind数据库。我得到的公司名称及其订单值的总和（以下代码）。现在，我想检查公司的订单价值是否大于平均水平，但我从查询中获得的平均价值与总和相同。如果Orders_Value> avg_order_value，我也无法查询。

我尝试这样做：

having Orders_Value > avg_order_value;

但它不适用于：

SELECT CompanyName, AVG(Orders_Value) as avg_order_value
FROM
(SELECT  C.CompanyName, SUM(OD.Quantity * OD.UnitPrice) as Orders_Value 
FROM dbo.Customers as C
JOIN dbo.Orders as O on C.CustomerID = O.CustomerID
JOIN dbo.[Order Details] as OD on O.OrderID = OD.OrderID
GROUP BY  C.CompanyName)
as inner_query
GROUP BY  CompanyName;