SQL Server 2012 introduces a new feature called Contained Database
Authentication. The Contained Database Authentication feature allows the
database to partially contain the data that was previously stored
outside the database.
How to create contained database users with SQL Server 2012 Management Studio? See
Connecting to database using Contained Database Authentication
You need to specifically specify the database name on which you want to
connect or tell exactly which database to authenticate the user; for
that go to the Connection Properties page as shown below and specify the
name of the database and then try connecting.
Once successfully authenticated and connected to the database, the user will see the database.