Uninstalling SQL Server 2012

Back up your data. Although this is not a required step, you might have databases that you want to save in their present state. You might also want to save changes that were made to the system databases. If either situation is true, make sure that back up the data before you uninstall SQL Server. Alternatively, save a copy of all the data and log files in a folder other than the MSSQL folder. The MSSQL folder is deleted during uninstallation.
The files that you must save include the following database files:
- Master.mdf
- Mastlog.ldf
- Model.mdf
- Modellog.ldf
- Msdbdata.mdf
- Msdblog.ldf
- Mssqlsystemresource.mdf
- Mssqlsustemresource.ldf
- Tempdb.mdf
- Templog.ldf
- ReportServer[$InstanceName] (This is the Reporting Services default database.)
- ReportServer[$InstanceName]TempDB (This is the Reporting Services default temporary database.)
Delete the local security groups. Before you uninstall SQL Server, delete the local security groups for SQL Server components.
Stop all SQL Server services. We recommend that you stop all SQL Server services before you uninstall SQL Server components. Active connections can prevent successful uninstallation.
Use an account that has the appropriate permissions. Log on to the server by using the SQL Server service account or by using an account that has equivalent permissions. For example, you can log on to the server by using an account that is a member of the local Administrators group.

To begin the uninstall process, go to Control Panel and then Programs and Features.
Right click Microsoft SQL Server 2012 and select Uninstall. Then click Remove. This starts the SQL Server Installation Wizard.
Setup Support Rules runs to verify your computer configuration. To continue, click Next.
On the Select Instance page, use the drop-down box to specify an instance of SQL Server to remove, or specify the option to remove only the SQL Server shared features and management tools. To continue, click Next.
On the Select Features page, specify the features to remove from the specified instance of SQL Server.
Removal rules runs to verify that the operation can complete successfully.
On the Ready to Remove page, review the list of components and features that will be uninstalled. Click Remove to begin uninstalling
Immediately after you uninstall the last SQL Server 2012 instance, the other programs associated with SQL Server 2012 will still be visible in the list of programs in Programs and Features. However, if you close Programs and Features, the next time you open Programs and Features, it will refresh the list of programs, to show only the ones that are actually still installed.