What is the average rating for right-footed players and left-footed players?
SELECT preferred_foot ,  avg(overall_rating) FROM Player_Attributes GROUP BY preferred_foot
SELECT preferred_foot ,  avg(overall_rating) FROM Player_Attributes GROUP BY preferred_foot
[{'preferred_foot': None, 'avg(overall_rating)': None}, {'preferred_foot': 'left', 'avg(overall_rating)': 68.6261820132788}, {'preferred_foot': 'right', 'avg(overall_rating)': 68.59155835241928}]