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Why would a zip code make a bad primary key for an individual in SQL?
ZIP codes cross city, county, and state lines which makes it uniquely poor as a key (postal codes in other countries may not be as problematic but data modelers always have to worry about the worst case). Plus, ZIP codes change over time for an address which is not something you want in your primary keys.
Which would make good choices for primary keys?
What Makes a Good Primary Key?
- The primary key should consist of one column whenever possible.
- The name should mean the same 5 years from now as it does today.
- The data value should be non-null and remain constant over time.
- The data type should be either an integer or a short, fixed-width character.
What is the difference between primary key and natural key?
The primary key is a unique value that identifies each record. A natural key is a single column or set of columns that uniquely identifies a single record in a table, where the key columns are made up of real data.
Which datatype is used for address in SQL?
String data types are normally used to store names, addresses, descriptions or any value that contains letters and numbers including binary data, like image or audio files. Stores fixed-length character string.
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.
How to choose a primary key in a database?
We’ll start with how to choose a Primary Key, fight an identity crisis, and then finish with code samples for creating a Primary Key in a database. You may think Luke is the only one with an identity crisis, but that’s not true. When creating a database, everything is in an identity crisis.
Do you need a primary key for an address table?
In general, given that addresses tend not to have anything that works as a natural primary key, your address table will need a synthetic primary key ( address_id) that has no meaning and simply acts as a primary key. Databases have different ways to generate synthetic primary keys, sequences and auto-incrementing columns are common approaches.
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.