如何管理数据库中的用户角色?

I'm creating a website in which I will be managing users and their permissions. I am looking to implement user roles, and can't seem to wrap my head around how things should work. I want to be able to assign a user a certain role, and have each role contain one to several permissions that can be read easily by my script. Just want to know how I should go about setting up my database to do this easily and efficiently.I'm creating a website in which I will be manag