Topic 14824 min readStructured Tutorial
Understanding Non-Clustered Indexes in SQL
Quick Answer
A non-clustered index in SQL is a separate data structure that improves query performance by maintaining a sorted list of key values and pointers to the actual data rows. Unlike clustered indexes, it does not alter the physical order of the data, allowing multiple non-clustered indexes per table to optimize different queries.
Learning Objectives
- Define what a non-clustered index is and how it differs from a clustered index.
- Explain how non-clustered indexes improve query performance.
- Identify scenarios where non-clustered indexes are beneficial.
Introduction
Indexes are essential for speeding up data retrieval in SQL databases.
A non-clustered index is one of the primary types of indexes used to optimize queries without altering the table's physical data order.
An index is like a table of contents for your database.
