data:modeling:natural_key

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About

A natural key is a type of primary key that is not controlled by your system.

Examples are all state identifications such

the VIN number for your car
the VAT number of your company
the SSN (social security number) for a person

This type of key is rarely used in practice as primary key because:

they may change (they are not controlled by your system)
they may not be available (people are not required to reveal their SSN)

If a primary key is not natural, it's a surrogate key (the most used type of primary key)

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