Microsoft® SQL Server 2008 R2 Unleashed
by Ray Rankins, Paul Bertucci, Chris Gallelli, Alex T. Silverstein
Logins
Every principal granted security to SQL Server must have an associated login. The login provides access to SQL Server and can be associated with principals scoped at the Windows and server levels. These logins can be associated with Windows accounts, Windows groups, or SQL Server logins.
Logins are stored in the master database and can be granted permission to resources scoped at the server level. Logins provide the initial permission needed to access a SQL Server instance and allow you to grant access to the related databases. Permissions to specific database resources must be granted via a database user. The important point to remember is that logins and users are directly related to each other but are different entities. It is possible ...