Hi! How are you?  Can you show me a list of all of the country names?
select name from country
Great!  Can you update this list to include the average roller coaster speed for each of these three countries?
select t1.name, avg ( t2.speed ) from country as t1 join roller_coaster as t2 on t1.country_id = t2.country_id group by t1.name
Thank you for that!  Would you be able to show me the roller coaster names associated with just Sweden?
select t2.name from country as t1 join roller_coaster as t2 on t1.country_id = t2.country_id where t1.name = 'Sweden'