List the position of players with average number of points scored by players of that position bigger than 20.
return players  ;return positions of   #1 ;return points scored by #1 ;return number of  #3 for each #1 ;return the  average of   #4 for each #2 ;return #2 where #5 is  bigger than  20
['select', 'project', 'project', 'group', 'group', 'comparative']