ConfigMgr Client Approved Collections
This collection will allow you to find machines that need approval.
For Is Approved
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 inner join SMS_CM_RES_COLL_SMS00001 on SMS_CM_RES_COLL_SMS00001.ResourceId = SMS_R_System.ResourceId where SMS_CM_RES_COLL_SMS00001.IsApproved= '1'
Replace this section for not approved and unknown
For not aporved
SMS_CM_RES_COLL_SMS00001.IsApproved= '0'
For Unknown
SMS_CM_RES_COLL_SMS00001.IsApproved= '2'
FYI, I did not write this collection, I can not find who did but will gladly give credit to whom ever it was :-)