Trying to find vehicles which are free between 2 variable dates

Question

I\'m trying to find out which, if any, vehicles are free between a pair of user input variables as dates.

Each vehicle, which is being used for a trip, has a start and e

Answer 1

You're using AND, which implies both conditions have to be true. You need to use OR instead:

select vehicle_registration
  from trips
 where departure not between :departure and :return
    or return not between :departure and :return

On a side not, as indicated by the syntax highlighting, return is a bad name from a column name. It's a reserved word in Oracle and you should avoid it if you can.