Natural key [NK]

Natural keys are keys that can be used to identify entities in the domain. They must exist in the source system. For example: customer code, order number, etc.

In our datawarehouse we create a new key, called a surrogate key. This key is usually an incrementing integer.

A natural key can be primuary or foreign. For example the table Customer has the following columns:

customer_id        : surrogate key
customer_code   : primary natural key
country_code     : foreign natural key

The primary natural key can be used for historization.

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