SQL Query - Trouble with null Date and Join

SELECT * 
FROM Customer 
   LEFT JOIN Order ON Customer.??? = Order.???
WHERE orderDate > @passedInOrderDate

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-- 1) Customers that do not have records that have an orderDate > @passedInOrderDate
SELECT * 
FROM Customer 
   LEFT JOIN Order ON Customer.CustomerID = Order.CustomerID
WHERE CustomerID NOT IN (SELECT DISTINCT CustomerID FROM Customer WHERE orderDate > @passedInOrderDate

-- 2) Customers that do not have any Order records at all 
SELECT * 
FROM Customer 
   LEFT JOIN Order ON Customer.CustomerID = Order.CustomerID
WHERE Order.CustomerID IS NULL

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DECLARE @passedInOrderDate DATE = '20170801';

SELECT C.*
FROM   PayPerClick.Customers C
       LEFT JOIN Orders O ON O.CustomerID = C.CustomerID
                             AND O.orderDate > @passedInOrderDate
WHERE  O.OrderID IS NULL;

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