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Is zip code a good primary key?
ZIP codes do not make good primary keys for a table of towns. If you’re making a simple lookup table of cities, ZIP code seems to be a logical primary key. However, upon further investigation, you might realize that more than one town shares a ZIP code.
Can a street address be a primary key?
Primary Keys You can think of the primary key as an address. If the rows in a table were mailboxes, then the primary key would be the listing of street addresses. When a primary key is composed of multiple columns, the data from each column is used to determine whether a row is unique.
Is a postal code a zip code?
ANSWER: The two codes are essentially the same in their purpose, but the term Zip code is mainly used in the USA; Postal Code is commonly used in other countries.
How to normalize an address to a ZIP code?
Normalization: ‘zip code’ as a primary key. An address is an address and should be in an address table. A zip code is an American postal code, and should be in a postal code table. An address is usually composed of some other info and a postal code, except in say Ireland, where they don’t have postal codes.
Why are primary keys important in database normalization?
Primary Keys Primary keys are a database constraint allowing us to implement the first and second normal forms. The first rule to follow to reach first normal form says “There are no duplicated rows in the table”. A primary key ensures two things:
Can a ZIP code be used as a primary key?
Normalization: ‘zip code’ as a primary key. A zip code is an American postal code, and should be in a postal code table. An address is usually composed of some other info and a postal code, except in say Ireland, where they don’t have postal codes. So a global, long-term solution does not use a postal code as a primary key for an address.
What is the dependency between ZIP code and address?
The dependency between the zip code and the address is called as a transitive dependency. To comply with the third normal form, all you need to do is to move the Street, City and the State fields into their own table, which you can call as the Zip Code table. −