You perform an in-place upgrade by running the SQL Server Installation Center. On the Installation page, you can invoke the Upgrade Wizard to upgrade from SQL Server 2005, 2008, or 2008 R2 (see Figure 9.15). The major steps performed by the SQL Server 2012 Installer program when performing an in-place upgrade include the following:
1. First, the SQL Server 2012 Setup prerequisites (Microsoft .NET Framework 3.5 Service Pack 1 (SP1) or a later version, SQL Server Native Client, and so on) are installed.
2. The Installer checks for issues that would prevent an upgrade. If it finds any, it will list them, and you must fix them and restart the upgrade process.
3. Setup installs the required SQL Server 2012 executables ...