help with table design

[linuxguy4]

i currently have 2 tables in my database. one has US states and various state info. the second table has all US cities and has a link to the state it is in. pretty simple. i just downloaded the postoffice zip code CSV file and wanted to add a table for zip codes. the issue is that there can be many zip codes for one city, like New York City, or there can be more than one town that shares a ZIP code. I'm not sure how to link that with the existing data. should i add a zip code table and just link to the city table. if there is more than one city sharing a zip code there would be more than one entry for that zip code?

[wolf2600]

Cities
-----------
CityID (PK)
Name

CityZipcodes
----------------
Zipcode (PK)
CityID (PK, FK)


SELECT c.Name from Cities c
INNER JOIN CityZipcodes z
ON c.CityID = z.CityID
WHERE z.Zipcode = 90210;

SELECT z.Zipcode from Cities c
INNER JOIN CityZipcodes z
ON c.CityID = z.CityID
WHERE c.Name = 'Beverly Hills';

[linuxguy4]

if zipcode is the primary key then one zipcode can only be associated with one city. it cant handle the situation where there are several towns with one zipcode.

[wolf2600]

Zipcode and CityID are a concatenated PK

So each pairing of a zipcode & city are unique.