create table Customers (
 CustomerID int,
 FirstName varchar(30),
 PreferredName varchar(30),
 LastName varchar(30)
);

insert into Customers (CustomerID, FirstName, PreferredName, LastName)
values (1, 'John', NULL, 'Smith'), (2, 'Jane', NULL, 'Smith'),  (3, 'Robert', 'Bob', 'Jones');