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A natural key (also known as business key) is a type of unique key, found in relational model database design, that is formed of attributes that already exist in the real world. It is used in business-related columns. In other words, a natural key is a candidate key that has a logical relationship to the attributes within that row. A natural key is sometimes called domain key.
The main advantage of a natural key over a surrogate key (which has no meaning outside the database environment) is that a natural key already exists, so there is no need to add a new, artificial column to the schema. Using a natural key (when one can be identified) also simplifies data quality: It ensures that there can only be one row for a key; this single version of the truth can be verified because the natural key is based on a real-world observation.