How many parks does each city have?
select city, count(*) from park group by city
Which cities have 2 or more parks?
select city from park group by city having count(*) >= 2;
Which cities have 3 or more parks?
select city from park group by city having count(*) >= 3;
How about those with 2 to 4 parks?
select city from park group by city having count(*) between 2 and 4;