SELECT avg(Order_Quantity) FROM Invoices WHERE payment_method_code  =  "MasterCard"
Check the invoices record and compute the average quantities ordered with the payment method "MasterCard".
SELECT avg ( Order_Quantity ) FROM Invoices WHERE payment_method_code = `` MasterCard ''
select avg ( order_quantity ) from invoices where payment_method_code = value
Check the invoices record and compute the average quantities ordered with the payment method `` MasterCard '' .