ERROR 3146: Duplicate columns in select list of projection not allowed

create table parent
(
parent_id int,
description varchar(20),
child01 number,
child02 number
);

create table child
(
child_id int,
child_description varchar(20)
);

insert into parent values (1,'Parent 01',100,200);
insert into child values (100, '1hundred');
insert into child values (200, '2hundred');
commit;

=> select * from parent;
 parent_id | description | child01 | child02
-------------+---------------+----------+---------
         1      | Parent 01   |     100   |     200

=> select * from child;
 child_id | child_description
-----------+-------------------
      100  | 1hundred
      200  | 2hundred

=> select
-> parent.parent_id,
-> first_child.child_description first_child_description,
-> second_child.child_description second_child_description
-> from parent,
->      (select child_id first_child_id, child_description from child) first_child,
->      (select child_id second_child_id, child_description from child) second_child
-> where parent.child01 = first_child.first_child_id
-> and parent.child02 = second_child.second_child_id;

 parent_id | first_child_description | second_child_description
-------------+-----------------------------+--------------------------
         1      |      1hundred                | 2hundred

=> create projection parent_child_projection
-> as
-> select
-> parent.parent_id,
-> first_child.child_description first_child_description,
-> second_child.child_description second_child_description
-> from parent,
->      (select child_id first_child_id, child_description from child) first_child,
->      (select child_id second_child_id, child_description from child) second_child
-> where parent.child01 = first_child.first_child_id
-> and parent.child02 = second_child.second_child_id;
ERROR 3146:  Duplicate columns in select list of projection not allowed

=> create view parent_child_view
-> as
-> select
-> parent.parent_id,
-> first_child.child_description first_child_description,
-> second_child.child_description second_child_description
-> from parent,
->      (select child_id first_child_id, child_description from child) first_child,
->      (select child_id second_child_id, child_description from child) second_child
-> where parent.child01 = first_child.first_child_id
-> and parent.child02 = second_child.second_child_id;

CREATE VIEW

=> select * from parent_child_view;
 parent_id | first_child_description | second_child_description
-------------+-----------------------------+--------------------------
         1      | 1hundred                     | 2hundred