stopping access to a database

I configuring 2 databases:

    1/ One be on a https server, and all important data will be encrypted. The only use this
database will see are:
        A/ Updates 2-3 times a day, max.
        B/ Exporting a smaller set of 'unnormalized' tables for the database below.
    2/ A publically accessible, (through PHP applications), database that has less secure data
on it and is not encrypted.

I would like to stop accesses to database 2, delete all records in the 2-4 tables, and reimport
new records. How would I do this as a user on the system, not as an admin?