htmanning has asked for the wisdom of the Perl Monks concerning the following question:
I have a database of condo units. Some of the units rent a storage locker, and their locker number is in their database record if they rent one. I'm trying to find out which lockers are not rented. It's easy for me to display the ones which are rented out because I just search the database for records whose locker field is not empty. There are 25 lockers total. If I have 80 database records and 24 have lockers, how do I find the locker number that is not already taken? Make sense?