Unique Identifier from Two Tables
I have a database of ticket sales I need help with. We have a table for Events, Contacts, and Participations (contact ID, Event ID, and a unique ParticipationID). Then I have another table for Guests linked to Participation. That means that Participants can bring Guests to an event. All's well so far.
I then created another table called Seat List, whose purpose was to maintain a list of seats at the various theaters we use, and sometimes use the seat list for temporary seating arrangements at an event. The goal is to limit the number of seats and put guests in the seats next to their friends and the organizations they represent. The Seating ID is unique in both tables and there can only be one guest in a seat and if I try to put two guests in a seat the program spits back a revert field contents error message. All's still well.
It works great for a year, but when another year comes up and I want to do the event again I would rather not create a whole new seat list because chances are they will be sitting at the same seat (or a different one) and the database will show the seat as occupied.
Could I add the year or EventID to the SeatID to create a new composite unique identifier? Can a calculation like that be indexed and unique? The SeatID in the Guest List must relate to the Seat List so I can show the Guest a card with their Region, Section, Table, and Seat.