SCCM Clients missing

SCCM Clients missing:

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.Client is null order by SMS_R_System.Client