มณฑลที่ไม่มีชื่อเมืองมีชื่ออะไรบ้าง?ไม่จำเป็นต้องใช้ตารางทั้งหมด
What are the names of counties that do not contain any cities?It is not neccessary to use all the tables.
 county_public_safety:  county_id [ number]  name [ text]  population [ number]  police_officers [ number]  residents_per_officer [ number]  case_burden [ number]  crime_rate [ number]  police_force [ text]  location [ text] 
SELECT name FROM county_public_safety WHERE NOT county_id IN (SELECT county_id FROM city)