SELECT CustomerName FROM Customer c
LEFT OUTER JOIN  CustomersOrders co ON c.CustomerID = co.CustomerID
WHERE co.CustomerID is null

CREATE TABLE Customer (CustomerID INT, CustomerName VARCHAR(200), Birthdate DATETIME);
INSERT INTO Customer
SELECT CustomerID,CustomerName,Birthdate
FROM (VALUES(1,'John Doe','1/1/1970 08:31 AM'),(2,'Jane Doe','1/1/1971 01:18 PM'),
            (3,'Jon Public','1/1/1972 11:58 PM'),(4,'Jane Public','1/1/1973 07:00 AM'),
            (5,'John Smith','1/1/1974 08:31 AM'))a(CustomerID,CustomerName,Birthdate);
            
CREATE TABLE [Order] (OrderID INT, [PO Number] VARCHAR(10), OrderDate DATETIME);
INSERT INTO [Order]
SELECT OrderID, [PO Number], OrderDate
FROM (VALUES(1000,'ABC123','1/1/2012 01:00 PM'),(2000,'112233','2/1/2012 02:00 AM'),
            (3000,'XYZ987','3/1/2012 03:00 PM'),(4000,'50000','4/1/2012 04:00 AM'),
            (5000,'Verbal','5/1/2012 05:00 AM'))a(OrderID, [PO Number], OrderDate);
            
CREATE TABLE CustomerOrders (CustomerID INT, OrderID INT, IsShipped VARCHAR(5));
INSERT INTO CustomerOrders
SELECT CustomerID, OrderID, IsShipped
FROM (VALUES(1,1000,'False'),(1,3000,'True'),(3,4000,'False'),(2,2000,'True'),
            (5,5000,'True'))a(CustomerID, OrderID, IsShipped);

SELECT *
FROM Customer cus
WHERE NOT EXISTS (SELECT 1 
                  FROM CustomerOrders ord 
                  WHERE cus.CustomerID = ord.CustomerID);