Contained Databases feature is introduced in SQL Server 2012.
User authentication for contained users (users with passwords) is performed by the contained database.
Contained users don't have to be granted access at the server level.
To create a contained user with password:
CREATE USER User_Name WITH PASSWORD = 'P@$$w0rd';
To create a Windows Authentication user in the contained database, that doesn't have a SQL Server login:
CREATE USER [DOMAIN\User_Name];
To connect to a contained database using a contained user credentials, you have to specify the contained database in the connection string.
Enter User name and Password:
Click Options to enter the database to connect to:
User is successfully connected to the database:
If you don't specify the database to connect to, connection will fail because SQL Server is looking for a login in master database that doesn't exist: