An index is a database structure that enhances the speed of data retrieval operations on a table. It’s created on one or more columns of a table to speed up SELECT, JOIN, and WHERE queries by allowing the database engine to quickly locate rows that match the indexed values.

Benefits of Indexes:

• Faster Queries: Indexes significantly improve query performance, as they enable the database engine to quickly locate the desired rows instead of scanning the entire table.
• Efficient Joins: Indexes on join columns speed up join operations by allowing the database to find matching rows faster.
• Constraint Enforcement: Unique indexes enforce uniqueness on columns, preventing duplicate values.
• Data Integrity: Indexes can enforce referential integrity between tables through foreign key constraints.

Example:

CREATE INDEX idx_last_name ON employees (last_name);

It’s important to note that while indexes enhance read performance, they can slow down write operations (INSERT, UPDATE, DELETE) because the index must be updated whenever the data changes.

In summary, views provide a way to create virtual tables for simplified data access and security, while indexes enhance query performance by allowing faster data retrieval. Both views and indexes play crucial roles in designing and optimizing a well-structured database.