Most efficient way to to find most expensive recent order - sql-server-2008

Question

I am trying to find most recent and expensive purchase by customer. I have four tables customers,orders,order details and product code. All accounts are unique by emailaddress.
Error The multi-part identifier "cx.EmailAddress" could not be bound
SELECT c.EmailAddress,
o.BillingFirstName AS WC_FirstName,
o2.LatestOrder
FROM Customers c
JOIN orders o ON o.customerid = c.customerid
JOIN( SELECT
cx.EmailAddress,
MAX(o.OrderID) AS LatestOrder
FROM Customers AS cx
JOIN Orders o ON o.customerid = cx.customerid
WHERE o.OrderStatus <> 'CANCELLED' AND o.OrderDate > '09/01/2017 00:00'
GROUP BY EmailAddress) AS o2 on o2.EmailAddress = cx.EmailAddress
GROUP BY c.EmailAddress,o.BillingFirstName
UPDATE Tried it in another way too but still gets error : The multi-part identifier "c.EmailAddress" could not be bound.
SELECT
c.EmailAddress,
c.CustomerID,
o.OrderDate,
p.Google_Gender,
p.Google_Age_Group ,
p.productprice AS Product_Price
FROM
Customers c
JOIN
orders o ON o.CustomerID = c.CustomerID
JOIN
(SELECT
c.EmailAddress,
MAX(o.OrderID) AS LatestOrder
FROM
Orders o, Customers c
WHERE
o.OrderStatus <> 'CANCELLED' AND
o.CustomerID = c.CustomerID
GROUP BY
c.EmailAddress) AS o2 ON o2.EmailAddress = c.EmailAddress
JOIN
(SELECT
od.*,
c.EmailAddress,
row_number() over (partition BY c.EmailAddress
ORDER BY od.ProductPrice DESC, o.OrderDate DESC) AS seqnum
FROM
OrderDetails od
JOIN
Orders o ON od.OrderID = o.OrderID
JOIN
Customers c ON o.CustomerID = c.CustomerID
JOIN
(SELECT
c.EmailAddress,
MAX(o.OrderID) AS LatestOrder
FROM
Orders o , Customers c
WHERE
o.OrderStatus <> 'CANCELLED' AND
o.CustomerID = c.CustomerID
GROUP BY
c.EmailAddress) AS o2 ON o2.EmailAddress = c.EmailAddress
WHERE
o.OrderID = o2.LatestOrder) od ON od.CustomerID = c.CustomerID
AND seqnum = 1
JOIN
Products_Joined p ON od.ProductCode = p.ProductCode
FULL JOIN
(SELECT p.ProductCode, p.ProductName FROM Products_Joined AS p) AS p2 ON p2.ProductCode = p.Google_Age_Group
WHERE
AND o.PaymentAmount <> 0
AND o.OrderID = o2.LatestOrder
GROUP BY
c.EmailAddress, o.OrderDate, c.CustomerID, p.productprice,
p.Google_Age_Group, p.Google_Gender, p.Google_Pattern,
p.Google_Size, od.ProductName, p.ProductName, p2.productname,
p.productcode
ORDER BY
o.OrderDate DESC, MAX(od.ProductPrice) DESC;

Answer 1

You have that error because cx is an internal alias inside the o2 query. So you should probably change that JOIN condition for this one:
AS o2 on o2.EmailAddress = c.EmailAddress
This way you join your o2 email address with the one from Customers directly.
Just for the sake of performance, it would be better if you join customers by CustomerID, like you do in your first join, instead of by email.
Finally, you are doing the MAX of OrderID, which will most likely return the most recent order. Having that in mind, you should probably change your query to something like this (I'm guessing Amount is the name of the field):
SELECT c.EmailAddress,
o.BillingFirstName AS WC_FirstName,
MostExpensiveOrderId = o.OrderId,
MostExpensiveOrderAmount = o.Amount
FROM Customers c
INNER JOIN (
SELECT
CustomerID,
MAX(Amount)
FROM Orders
WHERE OrderStatus <> 'CANCELLED' AND OrderDate > '09/01/2017 00:00'
GROUP BY CustomerID
) AS omax ON omax.CustomerID = C.CustomerID
INNER JOIN Orders o ON o.CustomerID = c.CustomerID AND o.Amount = omax.Amount
ORDER BY c.EmailAddress, o.BillingFirstName
Note that you don't need the Customers table in the inner query. Also note that this way you may get more than one row per customer if the highest value is shared with more than one order.