Question

I am re-creating a part of my company’s database because it does not meet future needs.
Currently we have mainly a flat file and some disjoined tables that were never fully realized.

My way of thinking is we have a table for each category except maybe the zips table, which may serve as a connect it all together table.
Please refer to image below:

Database Diagram http://www.freeimagehosting.net/uploads/248cc7e884.jpg

One thing I am thinking of is removing the zip table and just putting the zip code in the zipstocities table since the zip code is almost unique and then indexing the table on the zip code. The only downside is zip code has to be a varchar to take care of zip codes with leading zeros. Just want to know if there is a flaw in my logic.

Answer 1

I don’t know the US ZIPcode and territorial devision system well, but I assume it’s somewhat like the German one.

• A state has many counties.
• A county has many cities.
• A city has many zip codes.

Hence I would use the following schema.

ZipCodes          CityZipCodes
------------      ----------------      Cities
ZipCode (PK) <─── ZipCode (PK)(FK)      -----------
                  City    (PK)(FK) ───> CityId (PK)
                                        Name
                                        County (FK) ───┐
                                                       │
                                                       │
                                     Counties          │
                                     -------------     │
              States                 CountyId (PK) <───┘
              -----------------      Name               
              StateId      (PK) <─── State    (FK)
              Name
              Abbreviation

Fixed for multiple cities per ZIP code.