Lets add some data to the table.
SQL> insert into address_book 2 values (1, 'Ben Rockwood', '510-555-1234', '650-555-2345', 'Menlo Park, CA'); 1 row created. SQL> insert into address_book 2 values (2, 'Tamarah Rockwood', '510-555-4443', NULL, 'Menlo Park, CA'); 1 row created. SQL> insert into address_book 2 values (3, 'Nova Rockwood', NULL, NULL, 'Menlo Park, CA'); 1 row created. SQL>