A government organization provides data in a series of files which can be re-engineered and imported into a database. The files are updated monthly. I have been able to reengineer the database in MySQL and import the data. I've also created additional tables on the database and added my own data. My issue is I'm unsure as to how to handle updates to the database.
How do I import the data every month and sync it with the database from the previous month, which would include the tables that I added?