How about this?

; WITH RankedListed (CNo, CId, [Rank]) AS

(

SELECT T.CNO

,T.CId

,ROW_NUMBER()

OVER ( PARTITION BY T.CNO

ORDER BY CASE WHEN COUNT(*) = 1 THEN T.CId

ELSE COUNT(*)

END

DESC) AS 'Rank'

FROM #temp T

LEFT JOIN #temp1 T1

ON T.CNO = T1.CNo

AND T.CId = T1.CId

GROUP BY T.CNO

,T.CId

--ORDER BY T.CNO

--,T.CId

)

SELECT RL.CNo , RL.CId

FROM RankedListed RL

WHERE RL.[Rank] = 1

Thanks for posting the readily-consumable test data.