You should only have one copy of mysqld running, so as long as you are connecting to the proper port for that daemon, there's no need for the DB to 'be' in a particular location. MySQL keeps everything in one dir anyway, if I recall. You will of course need to send the proper "use <my_database_name>" command to the server once you are connected.
in reply to Pretty technical DBI question
If you aren't getting errors returned upon making the connection with the username/password, then the connection is working. You ARE checking return values, aren't you? [: