create new roles in sql server 2008

I have created a database system for a cms for a news website. I want to have only 4 roles in my db system : Admin, Author, Editor and Guest ( who only read the web pages). But there 开发者_StackOverflow社区are some pre-defined roles in every db system like sys and db_owner and… and they are not removable but I want the only 4 roles I mentioned above. How can I aim this goal? thanks

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ah, you cannot!

Also I do not think you will need to tweak the database system. Rather, architect a good solution for your application/frontend/website.

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as far as i am aware, you can't modify those roles (besides adding logins to them). instead of working around them, you could try using them, it might make life a little bit easier.