RFID Attendance - how to register "absence"?

This is for faculty monitoring wherein they would scan their cards to "log-in" to their specified class time schedule, logging-in would signify that they were "present" in that specified schedule. That is quite easy, the problem is, how could I register "absence" for time schedules? The "only" way I could think of, as of now, is to generate a record for each class schedule for each faculty and register it as "absent", only marking it as "present" when they have scanned their cards.

Any other idea you could suggest? TIA

I guess it depends on whether you want actual data or just a report. By a report I mean that you could generate an absentee list on demand using a join and 'NOT IN'. You could also have a tool that runs on a schedule and generates that list after each class and saves the result. Other than that, I agree that your only option would be to generate records for all expected and mark them as absent by default, updating as they scan in. Mind you, you'd need some tool executed automatically or manually to generate that list before the class so you could just as easily generate a list of only absentees after the class.

I would create rows for everyone so that we really know the possible population for that "date" and properly have it recorded in the database.