Show me the official names of the cities that have hosted more than one competition?
SELECT T1.Official_Name FROM city AS T1 JOIN farm_competition AS T2 ON T1.City_ID   =   T2.Host_city_ID GROUP BY T2.Host_city_ID HAVING COUNT ( * )   >  1
cities that have hosted more than one competition refers to COUNT(*) > 1; official names of the cities refers to Official_Name;