Show the ids and names of all mountains.
select id, name from mountain
Show the ids and names of those that have photos.
select t1.id, t1.name from mountain as t1 join photos as t2 on t1.id = t2.mountain_id
Which ones have at least 2 photos?
select t1.id, t1.name from mountain as t1 join photos as t2 on t1.id = t2.mountain_id group by t1.id having count(*) >= 2