hi,
i do not understand well what you exactly want...
the best way how to protect anybody else to access your tables is to set it on database level (access to database or tables). which database do you use? how do you access these tables? via php? and WHO is the another user - i.e. another user logged on the server, or somebody accessing WWW etc.
if you want to have it VERY secure, you can encrypt the content of the tables, too. but remember that there are then certain problems with indexes etc, so you must do it very carefuly.
bye, robert