SQL & PL/SQL

Hi,
I am from Italy... I hope my English is the most correct as possible.

I am studing Oracle bases.

I think I have understood differences between Pairwise comparison e Non pairwise comparison. But I don't have the table so I don't understand the example in the Oracle book:

NON PAIRWISE COMPARISON SUBQUERY:

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';

PAIRWISE COMPARISON SUBQUERY:

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

When those queries return some values?

Thanks for the help.

P.S.: I don't manage to do the symbol of "different" -> "<.>"

Edited by: user10992983 on 12-nov-2009 3.36