List the distinct vehicle ids used in lessons.
select distinct vehicle_id from lessons
For those, give the detail as well.
select t1.vehicle_id, t1.vehicle_details from vehicles as t1 join lessons as t2 on t1.vehicle_id = t2.vehicle_id group by t1.vehicle_id
What is the id and detail of the vehicle used in lessons for most of the times?
select t1.vehicle_id, t1.vehicle_details from vehicles as t1 join lessons as t2 on t1.vehicle_id = t2.vehicle_id group by t1.vehicle_id order by count(*) desc limit 1