SCDs With The Same Business Key

Hi all,

I've created a store dimension. Within the store dimension is a CityID column that is related to a City dimension. Currently this city dimension has the following columns:

CityID (primary key --- foreign key for the StoreDim)
CityName
CountyName
StateName
CountryName
...

My SCD's source is being loaded from a query to a Zip table that contains ZipCodes along with cityID, CountyID, StateID, and CountryID that can be joined out to their respective tables to find the information needed to populate my SCD. However, cities can have several number of zipcodes and several cities in different states can have the same names. This causes a problem with eliminating duplicates for my dimension as well as finding a suitable business key.

For example, let's take a case: Washington city, District of Columbia (county), District of Columbia (state), USA (Country)
Now, this city has SEVERAL zip codes so when I create my joins:


SELECT ...
FROM Zip Z
INNER JOIN City C
ON C.CityID = Z.CityID
INNER JOIN County Cty
ON Cty.CountyID = Z.CountyID


So this returns several CityIDs for the same city... which when I try to use for my SCD causes problems because i have several business keys based off my CityIDs so my dimension loaded would look like

CityID CityDesc CountyDesc StateDesc CountryDesc
1 Washington District of Columbia District of Columbia USA
2 Washington District of Columbia District of Columbia USA
3 Washington District of Columbia District of Columbia USA
4 Washington District of Columbia District of Columbia USA

I want to have just ONE record in my dimension for this city.... How would I do this and what would I use for a business key? Also any recommendations on which of these attributes should be historical attributes? I would appreciate any input you guys have.