SELECT v.VendName,
       AVG(DATEDIFF(DAY, p.OrderDate, p.DeliveryDate)) DeliveryDays
FROM dbo.Vendors v
    JOIN dbo.PurchaseOrders p
        ON v.VendorID = p.VendorID
WHERE p.DeliveryDate IS NOT NULL
      AND p.OrderDate >= '2015-10-01 00:00:00'
      AND p.OrderDate < '2016-01-01 00:00:00'
GROUP BY v.VendName
 
HAVING AVG(DATEDIFF(DAY, p.OrderDate, p.DeliveryDate)) >
(
    SELECT AVG(DATEDIFF(DAY, OrderDate, DeliveryDate))
    FROM dbo.PurchaseOrders
    WHERE DeliveryDate IS NOT NULL
          AND OrderDate >= '2015-10-01 00:00:00'
          AND OrderDate < '2016-01-01 00:00:00'
);

SELECT
 
 c.CategoryDescription,
       p.ProductName,
       SUM(od.QuotedPrice * od.QuantityOrdered) totalsales
FROM dbo.Products p
    JOIN dbo.Order_Details od
        ON p.ProductNumber = od.ProductNumber
    JOIN dbo.Categories c
        ON p.CategoryID = c.CategoryID
    JOIN dbo.Orders o
        ON o.OrderNumber =
 
 od.OrderNumber
WHERE o.OrderDate BETWEEN '2015-10-01' AND '2015-12-31'
GROUP BY p.CategoryID, c.CategoryDescription, p.ProductName
HAVING SUM(od.QuotedPrice * od.QuantityOrdered) >
(
    SELECT AVG(sumcategory)
    FROM
    (
        SELECT p2.CategoryID,
               p2.ProductNumber,
               SUM(od2.QuotedPrice * od2.QuantityOrdered) sumcategory
        FROM dbo.Products p2
            JOIN dbo.Order_Details od2
                ON p2.ProductNumber = od2.ProductNumber
            JOIN dbo.Orders o2
                ON o2.OrderNumber = od2.OrderNumber
        WHERE p2.CategoryID = p.CategoryID  --在外部查詢中過濾此類別
              AND o2.OrderDate BETWEEN '2015-10-01' AND '2015-12-31'
        GROUP BY p2.CategoryID, p2.ProductNumber
    ) s
    GROUP BY s.CategoryID
)
ORDER BY c.CategoryDescription, p.ProductName;