What types of indexes have you used in your SQL queries to optimize data search?

In SQL, the following types of indexes are commonly used to optimize data search:

• B-Tree index — the most common type, suitable for quick searches, sorting, and range queries.
• Hash index — effective for exact key lookups but does not support range queries.
• Unique index — ensures the uniqueness of values in a column, while also speeding up searches.
• Composite index — built on multiple columns, useful for queries filtering by several fields.
• Full-text index — used for fast searching within text data.

Example of creating a composite index:

CREATE INDEX idx_user_lastname_firstname ON users (lastname, firstname);

The choice of index type depends on the nature of the queries and the data structure.