What are the advantages and disadvantages of using natural keys in databases?

Natural keys are keys based on real, existing data in the domain, such as a passport number or Taxpayer Identification Number (TIN).

Advantages:

• Easy to understand and interpret, as they make sense in a business context.
• Do not require an additional field in the table, which can simplify the structure.

Disadvantages:

• They can change over time (e.g., phone number change), which complicates maintaining referential integrity.
• Often have a complex or large format, which can degrade index and join operation performance.
• They may be non-unique or absent in some cases, making them difficult to use as keys.

Ultimately, using natural keys is justified if they are stable, unique, and simple; otherwise, it is better to use surrogate (artificial) keys.