Which city has the smallest regional population?
select city from city order by regional_population asc limit 1
How many cities are there that have a regional population over 8000000 or under 5000000?
select count(*) from city where regional_population > 8000000 or regional_population < 5000000
Please show the names of these cities.
select city from city where regional_population > 8000000 union select city from city where regional_population < 5000000