How many more games were sold on game platform ID 50 than on game platform ID 51 in region ID 1?
result = subtract(sum(num_sales where game_platform_id = 50), sum(num_sales where game_platform_id = 51))
SELECT (SUM(CASE WHEN T.game_platform_id = 50 THEN T.num_sales ELSE 0 END) - SUM(CASE WHEN T.game_platform_id = 51 THEN T.num_sales ELSE 0 END)) * 100000 AS nums FROM region_sales AS T WHERE T.region_id = 1