[help] Possible To Script A Diff Into SQL Query?

My goal is to add a diff into a query that grabs data from 2 different tables.

The code:
SELECT
MIN(TableName) as TableName,
ID1, COL1, COL2, COL3, COL4, COL5, COL6, COL7, COL8
,COL9, COL10, COL11, COL12, COL13, COL14, COL15, --COL16,
COL17, COL18, COL19, COL20, COL21
FROM
(
SELECT 'Table A' as TableName,
SessionID as ID1,
StartDateCode as COL1,
StartTimeCode as COL2,
EndDateCode as COL3,
EndTimeCode as COL4,
HandledByCode as COL5,
DispositionCode as COL6,
DNISCode as COL7,
CallServiceQueueCode as COL8,
ApplicationCode as COL9,
IVREndPointCode as COL10,
BankCode as COL11,
TotalQueueTimeSS as COL12,
TotalAgentTalkTimeSS as COL13,
TotalAgentHoldTimeSS as COL14,
TotalAgentHandleTimeSS as COL15,
--TotalIVRTimeSS as COL16,
AfterHoursFlag as COL17,
SourceSystemID as COL18,
anubisTransferExtNumber as COL19,
anubisEndPoint as COL20,
AccountNumber as COL21

from [pdx0sql45].Rubicon_Marts.dbo.INB_Call_Fact
where startdatecode between 2738 and 2769

UNION all


SELECT 'Table B' as TableName,
SessionID as ID1,
StartDateCode as COL1,
StartTimeCode as COL2,
EndDateCode as COL3,
EndTimeCode as COL4,
HandledByCode as COL5,
DispositionCode as COL6,
DNISCode as COL7,
CallServiceQueueCode as COL8,
ApplicationCode as COL9,
IVREndPointCode as COL10,
BankCode as COL11,
TotalQueueTimeSS as COL12,
TotalAgentTalkTimeSS as COL13,
TotalAgentHoldTimeSS as COL14,
TotalAgentHandleTimeSS as COL15,
--TotalIVRTimeSS as COL16,
AfterHoursFlag as COL17,
SourceSystemID as COL18,
anubisTransferExtNumber as COL19,
anubisEndPoint as COL20,
AccountNumber as COL21

from pdx0sql04.Rubicon_Marts.dbo.INB_Call_Fact
where startdatecode between 2738 and 2769


) tmp

GROUP BY ID1, COL1, COL2, COL3, COL4, COL5, COL6, COL7, COL8
,COL9, COL10, COL11, COL12, COL13, COL14, COL15, --COL16,
COL17, COL18, COL19, COL20, COL21
HAVING COUNT(*) = 1
ORDER BY 2,1



---------

Is it possible to add a command into the query to output diff/compare scenario?

Thanks in advance for any help.