The prerequisite SQLServer 2008 R2 patch level for System Center Config Manager 2012(SCCM) is SP1 with Cumulative Update 6 (CU)
For a fresh install if you are considering the latest SQLServer 2008 R2 SP2 for SCCM 2012,then you need to understand the fact that SP2 includes hot fixes provided in SQL Server 2008 R2 SP1 Cumulative Updates 1 to 5 and do not include 6, 7 and 8.
You would need to deploy SQLServer 2008 R2 SP2 CU1 to ensure that you have the correct pre-requisites for SCCM 2012 deployment.
SQLServer 2008 R2 SP2 CU1 contains fixes released in SQL Server 2008 R2 SP1 CU 6 & 7.
SQL Services Blog states about this and you can read this here.
This patch level points are critical for your SCCM 2012 environment to work correctly.
Thanks for reading.