select TestA.CID,
(case when QTY2 != QTY then QTY2 else QTY end ) as QTY
from TestA
left join TestB on TestA.CID = TestB.CID
select TestA.CID,
(case when QTY2 != QTY then QTY2 else QTY end ) as QTY
from TestA
left join TestB on TestA.CID = TestB.CID