Find the id of courses which are registered or attended by student whose id is 121?
return students ;return ids of  #1 ;return #1 where  #2 is  121 ;return courses registered by #3 ;return courses attended by #3 ;return ids of  #4 ;return ids of  #5 ;return #6 or  #7
['select', 'project', 'comparative', 'project', 'project', 'project', 'project', 'union']