Design better databases
Tip for SQL users:If you give all your ID fields unique names, e.g. by calling your field "reservation_id" instead of "id", even in the reservation table, you can do stuff like:SELECT * FROM reservation JOIN guest USING (reservation_id);By doing "USING (reservation_id)" instead of "ON reservation.id = guest.reservation_id", the field will be automatically deduplicated, so you don't have to qualify it elsewhere in the query, and "SELECT *" will return only one copy.