[AccessD] question on normalization

Oh! I hadn't realized this was the problem -- I see what you're saying --
totally missed that possibility. 

Susan H. 

Unfortunately, while zip codes are supposed to be unique, they may be shared
among several small towns or a town may have multiple zip codes.
Some buildings even have unique zip codes, but generally zip codes belong to
post offices.  I would say they were not a good candidate for a primary key
in dealing with addresses.  I've worked with postal databases and seen some
of the "duplicate" zips, where several small towns share a post office and a
zip code.  A further complication is the
+four extension.