How does indexing in a database affect the speed and efficiency of query execution?

Indexing in a database significantly speeds up query execution, especially when searching, sorting, and filtering data. Indexes are created on one or more columns of a table and allow the DBMS to quickly find the needed records without scanning all rows (full table scan).

For example, if there is an index on the "id" field, then searching for a record with a specific id will be almost instantaneous, as the DBMS uses the index structure (such as a B-tree) for fast access.

However, indexes occupy additional space on disk and slow down insert, update, and delete operations, as the index also needs to be updated. Therefore, it is important to create indexes only where they genuinely improve query performance.