What types of indexes exist in SQL database management systems?

In SQL database management systems, there are various types of indexes that help speed up data search and sorting. The main types of indexes:

• B-Tree index — the most common type, suitable for most search, sorting, and range queries.
• Hash index — used for fast exact key lookups, but does not support range queries.
• Bitmap index — effective for columns with a small number of unique values (e.g., gender, status).
• Clustered index — an index that determines the physical order of data storage in a table.
• Non-clustered index — a separate structure pointing to the data location.

Each type of index is chosen depending on the nature of the queries and the data structure.