Microsoft SQL Server – User einem Login zuordnen

USE [dbname];
GO
EXEC sp_change_users_login 'Update_One' 'dbuser' 'login';
GO

http://msdn.microsoft.com/en-us/library/ms174378.aspx

USE [dbname];
GO
ALTER USER dbuser WITH LOGIN = login;
GO

http://msdn.microsoft.com/en-us/library/ms176060.aspx