There are some interesting reading in the supported configurations for WSUS in Server 2012 which is useful to know when you design your Configuration Manager 2012 environment with a Software Update role. I normally use the same SQL for WSUS as I use for Configuration Manager 2012 in many designs at customers. However there are some interesting reading on Technet about supported databases.
Right now Microsoft SQL Server 2012 is not supported so keep that in mind when upgrading your SQL or designing your Configuration Manager 2012 SP1 environment.
Windows Internal Database (WID)
Microsoft SQL Server 2008 R2 SP1 Standard Edition
Microsoft SQL Server 2008 R2 SP1 Enterprise Edition
Microsoft SQL Server 2008 R2 SP1 Express Edition
More information can be found here: http://technet.microsoft.com/en-us/library/hh852344.aspx
Another tip: the same article contains the recommended ant-virus exclusions for WSUS, which is highly recommended from a performance perspective. Note that the content directory is not heavily used when using WSUS with Configuration Manager.
\WSUS\WSUSContent where \WSUS\ is the location of the WSUS content folder
\SoftwareDistribution\Datastore (for client only)