I have a variable with year/month date values (i.e.. starting at 200601...going to 200809). This is the variable by which I'd like to subset my dataset - I'd like to include only those who are in there for every month from 200601-200809.

How do I select people based on this criteria (it can either be in Base SAS or proc sql)? I've tried the code below but neither seem to work.

Where date in: ('2006') and date in: ('2007') and date in: ('2008')

where left(date,4) = '2006' and left(date,4)='2007' and left(date,4) ='2008'