What are SQL indexes and how do they improve query performance?

What are SQL indexes and how do they improve query performance?

SQL indexes are special data structures that improve the speed of data retrieval operations on a database table. They work like a book's index, allowing the database to find data without scanning every row.

Can you explain the different types of indexes in SQL?

Sure! The main types of indexes in SQL are: 1. B-tree indexes, which are the most common; 2. Hash indexes, used for equality comparisons; 3. Full-text indexes, for searching text; and 4. GiST indexes, which support complex data types.

How do I create an index in SQL?

You can create an index using the CREATE INDEX statement. For example: CREATE INDEX index_name ON table_name (column_name); This will create an index on the specified column.

Are there any downsides to using indexes?

Yes, while indexes speed up read operations, they can slow down write operations like INSERT, UPDATE, and DELETE because the index also needs to be updated. Additionally, they consume extra disk space.