SQL & PL/SQL

I consult this link :http://stefan-armbruster.com/index.php/12-it/pl-sql/12-oracle-xml-and-json-goodies

use the SQL to create table:

create table ex01_person_tb (
  id number,
  name varchar2(50)
);
insert into ex01_person_tb values (1, 'Roger Waters');
insert into ex01_person_tb values (2, 'David Gilmour');
create table ex01_phone_tb (
  id number,
  person_id number,
  phone_number varchar2(50)
);
insert into ex01_phone_tb values (1, 1, '543 454433');
insert into ex01_phone_tb values (2, 1, '512 4776443');
insert into ex01_phone_tb values (3, 1, '521 6454423');
insert into ex01_phone_tb values (4, 2, '212 8332464');
insert into ex01_phone_tb values (5, 2, '312 6736423');

When I use this to query:

select a.id, a.name,
  cursor (select b.id, b.phone_number
  from ex01_phone_tb b
  where b.person_id = a.id) as phone_numbers
from ex01_person_tb a;

The message  is :[Err] ORA-00932: inconsistent datatypes: expected CHAR got DTYCWD.

Can you tell me how to resolve?