Give me a list of cities whose temperature in Feb is higher than that in Jun or cities that were once host cities?
select t1.city from city as t1 join temperature as t2 on t1.city_id = t2.city_id where t2.feb > t2.jun union select t3.city from city as t3 join hosting_city as t4 on t3.city_id = t4.host_city