Solution

The correct answer is Candidate key.

Key Points

• A candidate key is an attribute or a set of attributes that can uniquely identify a row in a table.
  • It is an alternative to the primary key in the table.
  • Each table can have multiple candidate keys, but only one primary key.
  • Candidate keys must contain unique values and cannot contain NULL values.
  • Examples of candidate keys include a combination of fields such as a person's social security number and email address.

Additional Information

• Candidate keys are essential in ensuring data integrity and preventing duplicate records in a database.
• While primary keys are often used as references for foreign keys, candidate keys provide flexibility in database design.
• In SQL, you can define candidate keys using unique constraints on the columns.
• Understanding candidate keys is crucial for database normalization and efficient query performance.