Show me all the engineers.
select * from maintenance_engineers
Show me id, first and last names of engineers who have visited.
select t1.engineer_id, t1.first_name, t1.last_name from maintenance_engineers as t1 join engineer_visits as t2 on t1.engineer_id = t2.engineer_id group by t1.engineer_id
Among those, which one made the least number of visits.
select t1.engineer_id, t1.first_name, t1.last_name from maintenance_engineers as t1 join engineer_visits as t2 on t1.engineer_id = t2.engineer_id group by t1.engineer_id order by count(*) asc limit 1