UPDATE: This post has now been superseded by SCCM Queries and the power of PRMVariable Name

select SMS_R_System.ResourceId, SMS_R_System.ResourceType, SMS_R_System.Name, SMS_R_System.SMSUniqueIdentifier, SMS_R_System.ResourceDomainORWorkgroup, SMS_R_System.Client from SMS_R_System where SMS_R_System.MACAddresses = “50:3F:56:00:BB:B4”

Results: