Roles provide a consistent yet flexible model for security administration. Roles are similar to the groups used in administering networks. Permissions are applied to a role, and then members are added to the role. Any member of the role has all the permissions that the role has.
The use of roles simplifies the administrative work related to security. Roles can be created based on job function, application, or any other logical group of users. With roles, you do not have to apply security to each individual user. Any required changes to permissions for the role can be made to the role security, and the members of the role receive those changes.
SQL Server has the following three types of roles:
• Fixed server and fixed database roles—