Join on ambiguous column name

Question

I have three tables I am working with. employee_passenger, nonemployee_passenger, employee (linked from another database). I want to outer join the passenger tables on the employee table for a view I am creating. Can I alias the two passenger tables and generically outer join both in one statement?
Example:
SELECT p.pk_passenger_id "Passenger_ID", n.pk_passenger_id "Passenger_ID", e.emp_id
FROM employee_passenger p, nonemployee_passenger n, employee@somewhere e
WHERE Passenger_ID = e.emp_id (+)
Desired result:
Passenger_ID Passenger_ID emp_id
101 9230
102
103 9249
Or would it be better to do something like:
SELECT p.pk_passenger_id, n.pk_passenger_id, e.emp_id
FROM employee_passenger p, nonemployee_passenger n, employee@somewhere e
WHERE p.pk_passenger_id IS NULL OR p.pk_passenger_id = e.emp_id

Answer 1

Consider the following approach:
First union both passenger tables, then join with the emp table (not tested).
SELECT p.pk_passenger_id Passenger_ID, e.emp_id, p.sourcetable
FROM (SELECT 'E' sourcetable, pk_passenger_id
           FROM employee_passenger
           UNION ALL
           SELECT 'NE' sourcetable, pk_passenger_id
           FROM nonemployee_passenger
           ) p,
           employee@somewhere e
WHERE p.pk_Passenger_ID = e.emp_id (+)