I have 2 tables: one with bus details (bus number, stations where the bus departs and arrives, associated schedules, number of available seats), one with traveler details (name, the station where the traveller starts his journey, the final station where he arrives).
Thanks a lot for your quick reply. That answers the questions that I asked. As an additional question, what would be the formula in order to compute the total number of passengers travelling on bus 201? I suppose that I would need to use the distinct or is there another solution? Thanks a lot. Annick