How do composite indexes improve database performance?

Composite indexes are created on multiple columns of a table simultaneously. They improve database performance by allowing efficient execution of queries that filter or sort data across several fields at once.

For example, if you have a table with columns city and date, and frequently run queries with conditions on both fields, a composite index on (city, date) will enable the database to quickly find the needed records without scanning the entire table.

It is important to note that the order of columns in a composite index matters: an index on (city, date) is effectively used for queries filtering by city or by both city and date, but not for queries only on date.

Thus, composite indexes reduce the number of read operations and speed up data retrieval, especially in complex search conditions.