Services
Technology Web App Development Mobile App Development Windows App Development Database Development UI/UX Development Cloud Development SEO Digital Marketing Guest Posting Content Writing Artificial Intelligence Data Science ERP Development CRM Development CMS Development LMS Development Business Listing Blockchain Technology Startup Promotion
Products
Data Converter Cleaner TUC - Unit Converter Import Export Survey Manager Tweet Controller
Developer
Article Blog Forum Interview Beginner News Startup Quiz
Users
Career
Apply Job Internship
Pricing
Login Sign Up Get a Quote

forum

home / developersection / forums / what is index? types of index in sql server
Ask Question

What is Index? Types of Index in SQL Server

Anubhav Sharma 354 15 Mar 2026

What is Index? Types of Index in SQL Server        

SQL Server sql server
Updated 05 Apr 2026
Anubhav Sharma
Anubhav Sharma

Student

The Anubhav portal was launched in March 2015 at the behest of the Hon'ble Prime Minister for retiring government officials to leave a record of their experiences while in Govt service .

Message

1 Answers

Ravi Vishwakarma
Ravi Vishwakarma 05 Apr 2026
Report Abuse

An Index in SQL Server is a database object that improves the speed of data retrieval from a table—just like an index in a book helps you quickly find a topic without scanning every page.

In Microsoft SQL Server:

An index creates a sorted structure (like a tree) that allows fast searching, filtering, and sorting of data.

Why Use Indexes?

  • Faster SELECT queries
  • Efficient searching and filtering
  • Improves JOIN, ORDER BY, GROUP BY performance

But:

  • Slows down INSERT, UPDATE, DELETE
  • Takes extra storage

Types of Indexes in SQL Server

1. Clustered Index

  • Physically sorts and stores the data in the table
  • Only one clustered index per table
  • Data rows are stored in order of the index key

Example:

CREATE CLUSTERED INDEX IX_Employee_Id
ON Employee(Id);

Use Case:

  • Primary key columns
  • Frequently sorted or range queries

2. Non-Clustered Index

  • Does not change physical order of table
  • Creates a separate structure with pointers to data
  • You can have multiple non-clustered indexes

Example:

CREATE NONCLUSTERED INDEX IX_Employee_Name
ON Employee(Name);

Use Case:

  • Frequently searched columns
  • Filtering (WHERE Name = 'John')

3. Unique Index

  • Ensures all values in the column are unique
  • Prevents duplicate entries

Example:

CREATE UNIQUE INDEX IX_Email
ON Users(Email);

4. Composite Index (Multi-Column Index)

Index on multiple columns

Example:

CREATE INDEX IX_Name_Department
ON Employee(Name, Department);

Use Case:

  • Queries using multiple columns in WHERE clause

5. Filtered Index

  • Index on a subset of data
  • Smaller and faster than full index

Example:

CREATE INDEX IX_ActiveUsers
ON Users(IsActive)
WHERE IsActive = 1;

6. Full-Text Index

  • Used for searching text data (large text fields)
  • Supports complex queries like word matching

7. Columnstore Index

  • Stores data column-wise instead of row-wise
  • Best for analytics and reporting

Use Case:

  • Large datasets
  • Data warehousing

8. XML Index

Used for querying XML data efficiently

9. Spatial Index

Used for geographic or spatial data

Clustered vs Non-Clustered (Quick Comparison)

Feature Clustered Index Non-Clustered Index
Data Storage Physically sorted Separate structure
Count One per table Multiple allowed
Speed Faster for range queries Faster for lookups

When to Use Indexes

  • Columns used in WHERE, JOIN, ORDER BY
  • Frequently queried columns
  • Large tables

When NOT to Use

  • Small tables
  • Frequently updated columns
  • Too many indexes (can reduce performance)

Simple Analogy

  • Clustered Index → Like a dictionary (data is sorted A–Z)
  • Non-Clustered Index → Like a book index (points to page numbers)
MindStick Training