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

Something like this, although I may have got the >= mixed up. Assuming a vehicle table and vehicle_id being the primary key/foreign key:

This method has the added benefit of showing vehicles that haven't yet been booked for a trip.

Select
  v.*
From
  vehicle v
Where
  Not Exists (
    Select
      'x'
    From
      trips r
    Where
      r.vehicle_id = v.vehicle_id and
      :return >= r.departure and
      :departure <= r.return
)

Answer 2

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.