As a site owner you must be able to access the database. There is one pretty descent tool for managing the DB. It is called phpMyAdmin, but this is standalone tool and is not a part of Joomla at all. I would advise you to ask your server administrator if he already granted you some access to something like this. If you are asking for Joomla plungins, there aren't any on my mind right now. Try searching through Joomla Extensions Directory.
Regards,
Tomaž
