Show the builders of the railways.
select builder from railway
List the railway id and the location of each railway.
select t2.railway_id, t1.location from railway as t1 join train as t2 on t1.railway_id = t2.railway_id
Only keep the ones that are associated with more than one train.
select t2.railway_id, t1.location from railway as t1 join train as t2 on t1.railway_id = t2.railway_id group by t2.railway_id having count(*) > 1