[Oracle] Pairwise e Non-Pairwise Comparison

[Il Pazzo]

Cominciamo dal confronto "Non-Pairwise":

SELECT employee_id, manager_id, department_id
FROM    employees
WHERE  manager_id IN
                            (SELECT manager_id
                             FROM    employees
                             WHERE  first_name = 'John')
AND      department_id IN 
                            (SELECT department_id
                             FROM    employees
                             WHERE  first_name = 'John')
AND first_name <> 'John';

Purtroppo non ho questa tabella... Ho provato a farmela io... ma non capisco, quando questa query ritorna delle righe?