Setting Roles per page...

Hi there,
I would like to know how i can define what roles can view pages so i could potentially set them within the admin area of a site. I know you can do this within the web.config file but am keen to learn how i can do this from say a setting in the DB.
I have seen it done in many CMS's so there is bound to be a way to do it, could anyone help or guide me in the right direction please?


Thanks for looking :)
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