If you’ve been working with the RC0 version of SQL Server 2012 (formerly code named “Denali”), you are likely aware that the final release is now available as an evaluation download here, or from MSDN with in the Standard, Business Intelligence, and Enterprise editions.
If you want to a straight upgrade from the evaluation edition, it’s a relatively simple process. From the installation screen, select the Upgrade from a previous version of SQL Server option (it doesn’t list RC0, but it is the same process).
Select all of the appropriate options, and your server will be upgrade. However, if you want to move from the RC0 to one of the licensed editions, you could run into trouble. In my testing, what has happened is that parts of the installation will upgrade properly,, but others will fail. This can be seen from the instances screen when upgrade is run for a second time.
Unfortunately, the “left behind” instance can not be upgraded further, and now that this has been run, the Edition upgrade function will fail to work. In one case, I needed to do a complete SQL uninstall and then a reinstall. I’ve had more fun. The good news is that the reinstall did work.
The way to avoid this is to do the Edition upgrade first. If you’re unfamiliar with this, you can find it on the Maintenance tab of the SQL Server installation Center
Once you complete the edition upgrade, go ahead and perform the standard upgrade as you would with the evaluation version.