I am having doubt in peter_budo 's Mvc tutorial, in datbase design he has separate table for group mapping,
Even we can add seperate feild (like group) in user table itself to acheive the same result, Is there any advantage in seperate that, Pls some one guide me.
Sorry if anything wrong,

It's probably a normalization. Can you please provide some additional info, like a link to the tutorial you mentioned.

Yes, it is because of normalization. In this setup, a user can belong to multiple groups. By adding a column, as you suggested, this is not possible. It would be one user in one group.

thank a lot pritaeas,
For example if user belongs to staff and admin groups which group rights he will get
once again thanks

The database will just say he has both, what you do with it in your code is up to you.