In what cases and for which operations is indexing used in databases?

Indexing in databases is used to speed up search and data retrieval operations. 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.

Main cases of indexing application:

• Key-based search: when queries with WHERE conditions on certain columns are frequently executed.
• Sorting and grouping: indexes help accelerate ORDER BY and GROUP BY operations.
• Ensuring uniqueness: unique indexes guarantee the absence of duplicates.
• Relationships between tables: indexes on foreign keys speed up JOINs.

However, indexes occupy additional space and slow down insert, update, and delete operations, so they should be created consciously, based on typical queries.

Example of creating an index in SQL:

CREATE INDEX idx_user_email ON users(email);