So shall we conclude that it is not possible to install SQL 2008 R2 on Windows Core 2008 R2? I did try to do it following described steps but SQL installation ended with error when NetFx35 role has come into the game. SQL installer needs .Net 3.5 SP1 but it is not on the list of existing features. Please do correct me if this is not correct.
Your conclusion is incorrect as you can install SQL 2008R2 onto Windows Core. The issue you are having is explained in the article. See below.
Finally click on “Add or Remove Roles”. There are many roles and features you can install but .NET is what you will need to get the SQL Server installation going. Scroll down the list until you see “NetFx3-ServerCore”, select it and click on apply. Once completed you will be ready to install SQL server.
Since SQL 2012 is now available, you should try install it onto Core. The purpose of this article was to show that you can install SQL 2008R2 onto Core and to allow you to play with SQL and Core.