04. Create a function that returns the credit card number for a particular order.

create Function sales.DisplayCardNumber(@salesOrderID int)
Returns nvarchar(25)
as
begin
Declare @ret nvarchar(25)
select @ret=CardNumber
from sales.salesOrderHeader s join sales.CraditCard c
on s.CreditCardID=c.CreditCardID
Where salesOrderID=@salesOrderID
If (@ret is Null)
set @ret=0
Return @ret
end


select SalesOrderID,'Credit Card Number'=Sales.DisplayCardNumber
(SalesOrderID) from Sales.SalesOrderHeader