What database are you using?
Very basic protection includes setting a username and password for the user or users that are allowed to SELECT, UPDATE, DELETE, etc.
If you want to go into more detail you can usually restrict right down to column level.
If you are using MySQL I suggest you go and grab phpMyAdmin. It is a great web based database administration tool for MySQL. I think they even have a postgreSQL version now.
http://phpwizard.net/projects/phpMyAdmin/index.html
Good Luck!