How does a database index improve query performance?

A database index significantly enhances query performance by providing a method to quickly locate and access the rows in a table without having to scan the entire dataset. When an index is created on a table's columns, the database constructs a data structure that holds pointers (or references) to the specific rows in that table which contain the indexed values. This allows the database engine to efficiently retrieve the required data based on the indexed column values, speeding up search operations considerably.

For example, when a query is executed that searches for a specific value in a column that is indexed, the database can use the index to directly navigate to the location of that value, rather than examining each row sequentially. This results in a much quicker response time for queries, especially in large datasets.

On the other hand, the other options do not directly relate to how an index improves query performance. Reducing data redundancy focuses on minimizing duplicate data within the database, which can be beneficial for storage efficiency but does not inherently speed up queries. Increasing data volume does not improve performance; in fact, larger volumes often lead to slower query times unless properly indexed. Lastly, database normalization is a design process aimed at reducing data redundancy and increasing data integrity, but it operates independently from indexing, which is specifically