---
title: "What is a unique key?"  
description: "What is a unique key?"  
author: "Anonymous User"  
published: 2019-04-06  
updated: 2020-09-22  
canonical: https://www.mindstick.com/interview/23501/what-is-a-unique-key  
category: "database"  
tags: ["database", "sql server"]  
reading_time: 1 minute  

---

# What is a unique key?

The **Unique key** constraint uniquely identified each record in the database. This provides uniqueness for the column or set of columns.

The Primary key constraint has automatic unique constraint defined on it. But not, in the case of Unique Key.

There can be many unique constraints defined per table, but only one Primary key constraint defined per table.

\

## Answers

### Answer by Anonymous User

The **Unique key** constraint uniquely identified each record in the database. This provides uniqueness for the column or set of columns.

The Primary key constraint has automatic unique constraint defined on it. But not, in the case of Unique Key.

There can be many unique constraints defined per table, but only one Primary key constraint defined per table.

\


---

Original Source: https://www.mindstick.com/interview/23501/what-is-a-unique-key

Copyright © MindStick Software Pvt. Ltd. This Markdown version is provided for developers, AI systems, and offline reading.