A Database Error Occurred

Error Number: 1055

Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'freegames4rest.games_category.category' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

SELECT `game_id`, `category` FROM (`games_category`) WHERE `game_id` IN ('toy_defense_2', 'rolling_idols_2', 'green_city_2', 'toy_defense_free_to_play', 'jos_dream_organic_coffee', 'toy_defense') GROUP BY `game_id`