What is a database index and why is it used?

What is a database index and why is it used?

• A. A backup mechanism that copies data to remote sites.
• B. A policy for data retention.
• C. A data structure that speeds up data retrieval by allowing quick lookups.
• D. A routine for encrypting data at rest.

Answer: (C)

A database index is a data structure that speeds up data retrieval by allowing quick lookups. It organizes references to where data is stored so the database can locate rows without scanning every row, much like a book’s index helps you jump to the exact pages you need. This dramatically improves query performance, especially on large tables or for frequent search conditions. Keep in mind that while indexes speed reads, they add storage overhead and can slow down write operations because the index must be updated with any data changes. The other options describe different data-management activities—backing up data to remote sites, setting data-retention policies, or encrypting data at rest—not techniques for speeding up data retrieval.

A database index is a data structure that speeds up data retrieval by allowing quick lookups. It organizes references to where data is stored so the database can locate rows without scanning every row, much like a book’s index helps you jump to the exact pages you need. This dramatically improves query performance, especially on large tables or for frequent search conditions. Keep in mind that while indexes speed reads, they add storage overhead and can slow down write operations because the index must be updated with any data changes. The other options describe different data-management activities—backing up data to remote sites, setting data-retention policies, or encrypting data at rest—not techniques for speeding up data retrieval.