Find the name of route that has the highest number of deliveries.
create table delivery_routes (route_name varchar, route_id varchar, PRIMARY KEY (route_name)); create table delivery_route_locations (route_id varchar, PRIMARY KEY (route_id))
select t1.route_name from delivery_routes as t1 join delivery_route_locations as t2 on t1.route_id = t2.route_id group by t1.route_id order by count(*) desc limit 1