SELECT Customer_Id, SUM(total_amount) "Total"
	FROM Customer.Orders
	GROUP BY Customer_Id

    UNION

    SELECT Id as "Customer_Id", 0 as "Total"
    FROM Customer.Customer
    WHERE ID NOT In (SELECT distinct Customer_Id from Customer.Orders)

    ORDER BY Customer_Id;

    SELECT Count(*) as Total, Product_Id
    FROM Customer.Order_Item
    GROUP BY Product_Id
    HAVING Count(*) > 10
    ORDER BY Total;

    SELECT Count(co.Country_Code) as "Country Count", o.Name
    FROM World.Country_Organization co
    JOIN World.Organization o
      ON co.Organization_Code = o.Code
    GROUP BY o.Name
    ORDER BY o.Name;

    SELECT COUNT(c.Code) as "Country Count", c.Continent
    FROM World.Country c
    JOIN World.Country_Language cl
      ON c.Code = cl.Country_Code
    WHERE cl.Is_Official = 'T'
    GROUP BY c.Continent;