Natural Keys

• A natural key or natural identifier is a real-world identifier used to uniquely identify real-world objects

  • It is familiar to end users and forms part of their day-to-day business vocabulary

• Usually, if an entity has a natural identifier, a data modeler uses it as the primary key of the entity being modeled

A natural key can be any column or combination of columns that is unique within the data set and has a business meaning or semantic significance. For example, in a customer database, the natural key could be the customer's social security number, a unique identifier that is already assigned to the customer by a government agency. In a product database, the natural key could be the product's UPC code, a unique identifier assigned by the manufacturer.

The advantage of using a natural key is that it can provide meaningful information about the data being stored, making it easier for users to understand and query the data. However, natural keys can have their own set of challenges, such as the need to ensure their uniqueness and potential changes to the key over time. As a result, many databases use surrogate keys as the primary key to avoid these issues.