Single-user mode

(Source: msdn.microsoft.com)

Single-user mode specifies that only one user at a time can access the database and is generally used for maintenance actions.

Limitations and Restrictions

If other users are connected to the database at the time that you set the database to single-user mode, their connections to the database will be closed without warning.

The database remains in single-user mode even if the user that set the option logs off. At that point, a different user, but only one, can connect to the database.

Prerequisites

Before you set the database to SINGLE_USER, verify that the AUTO_UPDATE_STATISTICS_ASYNC option is set to OFF. When this option is set to ON, the background thread that is used to update statistics takes a connection against the database, and you will be unable to access the database in single-user mode.

ALTER DATABASE AdventureWorks2012

SET SINGLE_USER

WITH ROLLBACK IMMEDIATE;

GO