What is the role of indexes in a database and why are they used?

Indexes in a database are used to speed up the search and retrieval of data. They work like pointers or a table of contents in a book, allowing quick access to the needed records without scanning the entire table. Indexes are used to improve the performance of SELECT queries, especially with large volumes of data.

However, indexes occupy additional space and slow down insert, update, and delete operations because the index also needs to be updated. Therefore, it is important to create indexes only on columns that are frequently involved in search conditions or sorting.

Example: if you have a users table with an email column, and you often search for users by email, it is advisable to create an index on this column.