แต่ละเมืองมีการแข่งขันกี่ครั้ง? วาดแผนภูมิวงกลม ไม่จำเป็นต้องใช้ตารางทั้งหมด
How many competitions are held in each city? Draw a pie chart.It is not neccessary to use all the tables.
 city:  City_ID [ int]  Official_Name [ text]  Status [ text]  Area_km_2 [ real]  Population [ real]  Census_Ranking [ text] 
SELECT Official_Name, COUNT(Official_Name) FROM city AS T1 JOIN farm_competition AS T2 ON T1.City_ID = T2.Host_city_ID GROUP BY Official_Name