How does the use of indexes affect the query performance in a database?

Indexes in a database are used to speed up search and data retrieval. When queries involve conditions related to indexed columns, the DBMS can quickly find the required records without scanning the entire table.

Advantages of using indexes:

• Significantly accelerate SELECT operations with WHERE, JOIN, and ORDER BY clauses.
• Enable efficient handling of large volumes of data.

However, indexes occupy additional space and slow down insert, update, and delete operations, as the index also needs to be updated.

Example: if there is a users table with an index on the email field, the query

SELECT * FROM users WHERE email = 'example@mail.com';

will execute faster than without an index, as the DBMS quickly finds the required record using the index instead of scanning all rows.