SQL server 2008 : Managing Security - Users

Users are database-level principals that are created in order to access resources within a database. Database Users are typically mapped to a login, certificate, or asymmetric key. After you have created a login to SQL Server, you create a database user in order to provide permission to a database and the objects contained within. In order to more easily tie users back to logins, it is recommended that the Log-in and User names match. To aid in managing the organization of users permissions, users can be added to any one or more of the available database roles or to new roles that you create.

Users can be added to a database using the SQL Server Management Studio or by syntax such as:

CREATE USER user_name
   [ { { FOR | FROM }
     {
       LOGIN login_name
       | CERTIFICATE cert_name
       | ASYMMETRIC KEY asym_key_name
     }
     | WITHOUT LOGIN
]
[ WITH DEFAULT_SCHEMA = schema_name]

See Figure 1.

Figure 1. Database Users