Which statement about secondary keys is true?

Which statement about secondary keys is true?

• A. They enforce record uniqueness
• B. They prevent unauthorized access
• C. They improve lookup speed
• D. They are always the primary key

Answer: (C)

Secondary keys create alternate paths for locating data quickly through indexing on attributes other than the primary key. By building an index on a non-primary attribute, the database can use that index to find matching records without scanning the whole table, which speeds up lookups for queries that filter on that attribute. This is why improving lookup speed is the true statement. A secondary key does not enforce uniqueness by itself—uniqueness is a property of the primary key or of a separate unique constraint—and it isn’t a security feature. It also isn’t required to be the primary key; it’s simply an additional access path to data. In practice, multiple secondary keys can exist to support different query patterns, though they add some overhead for updates.

Secondary keys create alternate paths for locating data quickly through indexing on attributes other than the primary key. By building an index on a non-primary attribute, the database can use that index to find matching records without scanning the whole table, which speeds up lookups for queries that filter on that attribute. This is why improving lookup speed is the true statement. A secondary key does not enforce uniqueness by itself—uniqueness is a property of the primary key or of a separate unique constraint—and it isn’t a security feature. It also isn’t required to be the primary key; it’s simply an additional access path to data. In practice, multiple secondary keys can exist to support different query patterns, though they add some overhead for updates.