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 ('reel_deal_epic_slot_forrest_gump', 'epic_slots_rock_hero', 'reel_deal_slots_fishin_fortune', 'slot_quest_the_museum_escape', 'slot_quest_alice_in_wonderland') GROUP BY `game_id`