Why are indexes needed in databases? What are the disadvantages? What data structure is used for a standard index?

Indexes in a database are needed to speed up search and data retrieval. They allow quick finding of records without scanning all rows of the table.

Disadvantages of indexes:

• They take up additional disk space.
• They slow down insert, update, and delete operations because the index needs to be updated.

The standard data structure for an index is a B-tree. It provides a balanced tree with fast search, insert, and delete operations in logarithmic time.

Example: if you have a users table with an email field, an index on email will allow you to quickly find a user by email without scanning the entire table.