One of the easiest and fastest ways to clear all connections to a database is to use the following code (change the DB name, of course)... read the comments because there is a danger in doing so... and, keep in mind that this kills EVERYTHING with great prejudice. Any long-running transactions will take time to rollback. It also kills connections made by jobs. I'll say it again... it KILLS EVERYTHING. Use with care.

USE [master]

GO

--===== This kills everything except the connection running this command.

ALTER DATABASE [YourDbNameHere] SET SINGLE_USER WITH ROLLBACK IMMEDIATE;

--===== This sets it back to normal so that, if you lose the connection,

-- some app doesn't grab the only connection locking you out from it.

-- As an alternative, you could set it to restricted users but that

-- will also still let some apps in if they inappropriately have

-- the restricted privs

ALTER DATABASE [YourDbNameHere] SET MULTI_USER;

--===== Then, do your stuff immediately and without delay.