hmmm. I have not had to do that before. Someone else may jump in here or you may need to start a new thread specifying that as the issue.
You will need to figure out if you can do this but one might ...
import the access table into the SQL DB (likely as a custom named table so as to not create an issue with the existing schema) and at the time of import create a new column, short_zip, using the left(field,5) function. This way you have it all together and do not need to try and cross over the db types as well as a field to easily join on.
Anyone else?

Edited by DBlank - 15 May 2012 at 12:05pm