When I install SQL Server 2012 in a Windows Server 2008 R2 Core Mode,

Bumping into an error message "Setup detected an earlier version of SQL Server on your computer. This version is not supported on Windows Server Core installations. Before setup can proceed, you must uninstall the earlier version of SQL Server."

============= Solution ===============================================

Windows Server 2008 R2 Core下裝SQL Server 2012

僅支援以下Features

另外還需要

才能與SQL Server 2008 R2 裝在一起

/ACTION=install /UIMODE=EnableUIOnServerCore /SkipRules=ServerCoreBlockUnsupportedSxSCheck