Could you explain what is meant by a natural key in databases?

A natural key is a unique identifier for a record in a database, based on real, natural data rather than artificially created values. For example, in a user table, a natural key could be a passport number or TIN, if it is unique and unchanging.

Unlike a surrogate key (such as an auto-incremented ID), a natural key carries meaningful information and can be used for searching and linking data.

However, natural keys have disadvantages:

• They can be longer and more complex for indexing.
• Sometimes, the data used as a key can change, which is undesirable.

Therefore, the choice between a natural and a surrogate key depends on the specific task and data structure.