What is the average overall rating of the football player Aaron Doran?
average overall rating = AVG(overall_rating);
SELECT CAST(SUM(t2.overall_rating) AS REAL) / COUNT(t2.id) FROM Player AS t1 INNER JOIN Player_Attributes AS t2 ON t1.player_api_id = t2.player_api_id WHERE t1.player_name = 'Aaron Doran'