How many countries have more than 1 city?
select count ( * ) from ( select * from city as t1 join country as t2 on t1.country_id = t2.country_id group by t2.country_id having count ( * ) > 1 )
How many countries have at least 3 cities?
select count ( * ) from ( select * from city as t1 join country as t2 on t1.country_id = t2.country_id group by t2.country_id having count ( * ) > = 3 )
Show these countries
select t2.country from city as t1 join country as t2 on t1.country_id = t2.country_id group by t2.country_id having count ( * ) > = 3