>Sergey --
>
>I always start from the current month and look backward -- for right now, at least, I'm only looking back one year.
>
>So, indeed, if 200412 were missing for a partno, I'd want to get 2004121 as my result for that partno.

Hi Jim,

There're a few ways you can do that. You can create a cursor with list of last 12 periods with second column representing previous period and than run a query

CREATE CURSOR Parts (partno C(2), YYYYMM n(6), YYYYMMprev N(6))  
... Insert records here for the last 12 periods (month)
INSERT VALUES (200412, 200411)
...
INSERT VALUES (200401, 200312)

SELECT pn.partno, MAX(cp.YYYYMM) ;
FROM Parts pn ;
	JOIN crsPeriods cp ON cp.YYYYMMprev = pn.YYYYMM ;
	LEFT JOIN Parts pn2 ON pn.partno = pn2.partno ;
		AND cp.YYYYMM = pn2.YYYYMM ;
	WHERE pn2.partno IS NULL ;
GROUP BY pn.partno

You can also follow Hilmar's suggestions.