Can you list the main types of index structures used in MySQL?

The main types of index structures used in MySQL are:

• B-Tree: the most common type of index, used for fast searches, sorting, and range queries. Applied in PRIMARY KEY, UNIQUE, and INDEX types.

• Hash indexes: used in memory (Memory engine), providing very fast exact match searches but do not support range queries.

• Fulltext indexes: specialized indexes for full-text search in text fields.

• R-Tree indexes: used for spatial data (e.g., in MyISAM for geometric types).

Each index type is optimized for specific tasks, and the choice depends on the nature of the data and queries.