Using Oracle, I have a table:

Trips: (ID, Destination, Method, Fare)

Train: (ID, Railway, SeatClass, Trainspeed, NumberOfStops)

Using the Trips table, how can I write SQL to find a trip to the same destination that can be taken by car but is more expensive than by train? Is this a Union or Intersect?

Using Train Table I need to find the train trips that have the same speed.

Using Trips I need to find trips that have the same destination and method of travel and list them only once.

I also need to find the most expensive and the cheapest trip - I think I need to use min(fare) and max(fare) for this but how can I union the tables to get all the info? For example if I wanted to return the train details for the min(fare), how would I do that? I keep getting an error because the data values are not the same.