text: (SELECT first_name FROM actor 
  ORDER BY first_name)
  UNION 
  (SELECT first_name FROM customer 
  ORDER BY first_name);
  
  (SELECT first_name FROM actor
  ORDER BY first_name)
  INTERSECT 
  (SELECT first_name FROM customer
  ORDER BY first_name);
  
  (SELECT first_name FROM actor 
  ORDER BY first_name)
  EXCEPT
  (SELECT first_name FROM customer 
  ORDER BY first_name);
  
  -- tekrar eden veriler icin
  (SELECT first_name FROM actor 
  ORDER BY first_name)
  UNION ALL
  (SELECT first_name FROM customer 
  ORDER BY first_name);
  
  -- 2. ZATEN AYNI SONUCU VERIYOR
  
  (SELECT first_name FROM actor 
  ORDER BY first_name)
  EXCEPT ALL
  (SELECT first_name FROM customer 
  ORDER BY first_name);
  