Show the id of the camera lens that has taken picture of each mountain.
select camera_lens_id from photos
Which one has taken pictures of the most mountains.
select camera_lens_id from photos group by camera_lens_id order by count(*) desc limit 1
What is the name of this camera?
select t2.name from photos as t1 join camera_lens as t2 on t1.camera_lens_id = t2.id group by t2.id order by count(*) desc limit 1