---
title: "What is an Index in an SQL Server Database?"  
description: "What is an Index in an SQL Server Database?"  
author: "Ashutosh Patel"  
published: 2024-07-18  
updated: 2024-07-18  
canonical: https://www.mindstick.com/interview/33960/what-is-an-index-in-an-sql-server-database  
category: "mssql server"  
tags: ["mssql server", "sql server", "sql"]  
reading_time: 2 minutes  

---

# What is an Index in an SQL Server Database?

#### SQL Server Index

An index in a SQL database is a data structure that improves the speed of data retrieval in a database table at the expense of additional space and reduced performance in write operations

**Example-**\
Suppose you have a table `Employee` with the columns `emp_id`, `name`, `age`, and `department_id`. If you frequently search for employees based on their `emp_id`, creating an index on the `emp_id` column can greatly speed up those search operas

This SQL statement creates an index named `idx_employee_id` in the `emp_id` column of the `Employee` table.

```plaintext
CREATE INDEX idx_employee_id ON Employees(emp_id);
```

\
The database engine can use the `idx_employee_id` index to quickly find rows where `emp_id` is equal to `1001`, rather than scanning the entire `Employees` table sequentially.

```plaintext
SELECT * FROM employees WHERE employee_id = 1001;
```

**Also, Read:** [What are SQL Stored Procedures in the Database?](https://www.mindstick.com/interview/33957/what-are-sql-stored-procedures-in-the-database)

## Answers

### Answer by Ashutosh Patel

#### SQL Server Index

An index in a SQL database is a data structure that improves the speed of data retrieval in a database table at the expense of additional space and reduced performance in write operations

**Example-**\
Suppose you have a table `Employee` with the columns `emp_id`, `name`, `age`, and `department_id`. If you frequently search for employees based on their `emp_id`, creating an index on the `emp_id` column can greatly speed up those search operas

This SQL statement creates an index named `idx_employee_id` in the `emp_id` column of the `Employee` table.

```plaintext
CREATE INDEX idx_employee_id ON Employees(emp_id);
```

\
The database engine can use the `idx_employee_id` index to quickly find rows where `emp_id` is equal to `1001`, rather than scanning the entire `Employees` table sequentially.

```plaintext
SELECT * FROM employees WHERE employee_id = 1001;
```

**Also, Read:** [What are SQL Stored Procedures in the Database?](https://www.mindstick.com/interview/33957/what-are-sql-stored-procedures-in-the-database)


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