Calculate how many percent of sales in North America is higher than the average sale per region for platform ID 9577.
in North America refers to region_name = 'North America'; platform ID 9577 refers to game_platform_id = 9577; percent = divide(subtract(num_sales where region_name = 'North America' and game_platform_id = 9577, avg(num_sales)), avg(num_sales)) * 100%
SELECT (SUM(CASE WHEN T2.region_name = 'North America' THEN T1.num_sales ELSE 0 END) - AVG(T1.num_sales)) * 100.0 / AVG(T1.num_sales) FROM region_sales AS T1 INNER JOIN region AS T2 ON T1.region_id = T2.id WHERE T1.game_platform_id = 9577
database name:db_id video_games
genre table genre Cols: id dtype integer, genre_name dtype text, 
game table game Cols: id dtype integer, genre id dtype integer, game name dtype text, 
platform table platform Cols: id dtype integer, platform_name dtype text, 
publisher table publisher Cols: id dtype integer, publisher_name dtype text, 
game_publisher table game_publisher Cols: id dtype integer, game id dtype integer, publisher id dtype integer, 
game_platform table game_platform Cols: id dtype integer, game publisher id dtype integer, platform id dtype integer, release year dtype integer, 
region table region Cols: id dtype integer, region_name dtype text, 
region_sales table region_sales Cols: region_id dtype integer, game platform id dtype integer, number sales dtype real, 
