What does the primary key of a database table represent? What about its secondary key?

This question aims to assess your technical knowledge and understanding of database concepts, which are crucial for roles that involve data management and software development. Interviewers want to evaluate your familiarity with database design principles and how you apply them in practical scenarios. A solid grasp of primary and secondary keys indicates your ability to ensure data integrity and optimize database performance.

A primary key in a database table uniquely identifies each record, ensuring that no two rows can have the same value for that key. For example, 'In a customer table, the primary key might be the customer ID, which uniquely identifies each customer.' On the other hand, a secondary key provides a way to access records through a different field, often used for indexed searches. For instance, 'A secondary key could be the customer's email address, allowing for efficient lookups of customers when their email is known, but it is not unique.'