How to select set of 6 random numbers every time

/* 
  
  This SQL will a select a set of 6 random numbers every time it is run.
  
  The numbers will be between 1 and 49

*/

select r
 from ( select r
        from ( select rownum r
               from al_objects
               where rownum < 50 )
        order by dbms_random.value )
where rownum <= 6;