Kill all connections to a database in SQL Server

The easy and quick way to kill all connection to a SQL Server database is by setting the database to single user mode with ROLLBACK IMMEDIATE option.
This option will kill all the users immediately before setting the database to single user mode.
This will come handy while restoring a database and users are connected to it.

USE master
GO
ALTER DATABASE <DatabaseName>
SET SINGLE_USER
WITH ROLLBACK IMMEDIATE
GO
ALTER DATABASE <DatabaseName>
SET MULTI_USER
GO

How to invoke a SQL job from another Job present on a different instance

For invoking an SQL Server Job from another Job which is present on a different instance, we have different ways like

1. Create a Linked server and use msdb..sp_start_job to start the job
2. Using xp_cmdshell
3. Using SQLCMD Operating system command

In most of the SQL Server instances the xp_cmdshell will be disable due to security reasons and creating linked server is time consuming.

Uninstalling SQL Server Service Pack or Hotfix

Prior to SQL Server 2008, if you had to rollback a Service pack or hotfix installation, it was a long and hectic process as it involves rebuilding the SQL Server and restoring the user and system databases and setting up jobs, logins,etc... And in the meantime if you have missed backing up something then you are gone!
Starting from SQL Server 2008, Service Pack 1, microsoft has introduced an option to uninstall the service pack or an hotfix. It is as simple as uninstalling an application from your computer.
To uninstall an SQL Server service pack or hotfix,
Go to "Control panel" --> "Uninstall a Program" --> Click on "view installed updates" on left hand side
Choose the update you want to uninstall and click "Uninstall" option.

How to Restore model and msdb database

Unlike master database, restoring model and msdb is simple and follows the same procedure as restoring any other user database. However we have to be very cautious while restoring system databases as it will have sensitive data which is important for SQL Server to function without any issues.

How to Restore Master database

Before restoring master database, make sure

1. The build versions of the both instances (Current instance and the instance where backup is generated) should be the same.
• More Information at http://www.sanssql.com/2013/09/the-backup-of-system-database-on-device.html