What is the purpose of a database index?

• A. To store large binary data
• B. To speed up queries by locating rows quickly
• C. To enforce foreign keys
• D. To maintain transaction logs

Answer: (B)

Indexing in a database creates a fast lookup path for chosen columns. It’s like a map that stores the values of those columns alongside pointers to where the corresponding rows live. When you run a query with a condition on an indexed column, the database can jump directly to the relevant rows instead of scanning every row in the table. This makes data retrieval much quicker, especially in large tables. It’s not used for storing large binary data, enforcing foreign keys, or keeping transaction logs—that’s handled by other database features. So speeding up query locating of rows is the correct purpose of an index. Keep in mind that indexes take extra storage and can slow down writes because they must be updated too.