Database Systems Practice Test

Which statement defines an Index in databases?

A mechanism to ensure the uniqueness of records. A mechanism for increasing the speed of data search and data retrieval on relations with a large number of records. A feature to enforce referential integrity across all transactions. A technique to normalize data.

Correct Answer:

A mechanism for increasing the speed of data search and data retrieval on relations with a large number of records.

Explanation:

An index is a data structure that helps the database locate rows quickly by providing fast lookups on one or more columns. It works like a separate map that stores the indexed column values together with pointers to the actual rows, so the system can jump directly to the relevant data instead of scanning every row in a large table. This accelerates data search and retrieval, especially for queries in WHERE clauses, joins, or sorts on big relations. Keep in mind that indexes add some overhead for writes and extra storage, and they don’t by themselves enforce uniqueness or referential integrity (those are handled by constraints and keys), nor do they define how data is structured across tables, which is what normalization is about.

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