Did your "2012 draft league" database contain any player records or ballparks to begin with?

If you try to migrate your past season database to an empty database, what you'll end up with is a database with your team names and your league structure, but there will be no ballparks nor player records because as I mentioned in my earlier post, the migrate command does not copy or delete any player records (or ballparks) in either the old or new database. All it does is shuffle things around in the new season database based on the UID numbers. In other words, your target database ("New season database") needs to contain the player records and ballparks of the season you intend to base your new season on.