---
title: "What is Mapping Constraints in Database Management System ?"  
description: "What is Mapping Constraints in Database Management System ?"  
author: "Anonymous User"  
published: 2019-03-25  
updated: 2019-04-03  
canonical: https://www.mindstick.com/forum/34816/what-is-mapping-constraints-in-database-management-system  
category: "database"  
tags: ["database", "sql server", "dbms"]  
reading_time: 2 minutes  

---

# What is Mapping Constraints in Database Management System ?

[Define](https://yourviews.mindstick.com/audio/1110/lifestyles-choices-that-define-our-lives) it in brief. \

## Replies

### Reply by Rahul Roi

## Mapping Constraints in DBMS

![What is Mapping Constraints in Database Management System ?](https://www.mindstick.com/mindstickforums/50905aab-fec0-4277-a3dd-578564d3f777/images/8e03faea-e9b7-497d-b6d6-5d6e8fd08647.png) **\**

The mapping constraint is the data constraint that expresses the number of entities to which another entity can be related via a relationship set.

These are most useful in describing the relationship sets that involve more than two entity sets.

For binary relationship set R on an entity set X and Y, there are four possible mapping cardinalities. These are as follows:

- One to one (1:1)
- One to many (1: M)
- Many to one (M:1)
- Many to many (M: M)

**In one-to-one mapping (1:1):-** That is an entity of entity-set X can be associated with at most one entity of entity-set Y and an entity in entity-set Y can be associated with at most one entity of entity-set X.

![What is Mapping Constraints in Database Management System ?](https://www.mindstick.com/mindstickforums/50905aab-fec0-4277-a3dd-578564d3f777/images/63caa921-c04c-453d-91c3-f9ea848aafb4.png)\

**For Example** - Whether Employee and Department are 2 entity sets, then we can define a one to one relationship ‘Manages’ between an Employee entity and a Department entity i.e. one employee manages at most one department and one department is managed by at most one employee.

![What is Mapping Constraints in Database Management System ?](https://www.mindstick.com/mindstickforums/50905aab-fec0-4277-a3dd-578564d3f777/images/7e3ba228-ba1b-44a9-ac3a-58d11e8bedd0.png)

**One to many (1: M):-** When An entity of entity-set X can be associated with at most one entity of entity-set Y and an entity in entity-set Y can be associated with any number of entities of entity-set X.

![What is Mapping Constraints in Database Management System ?](https://www.mindstick.com/mindstickforums/50905aab-fec0-4277-a3dd-578564d3f777/images/a32b7828-f855-4faa-9f6e-71cc7fac69c5.png)

**Many to one (M:1):** When An entity of entity-set X can be associated with at most one entity of entity-set Y and an entity in entity-set Y can be associated with any number of entities of entity-set X.

![What is Mapping Constraints in Database Management System ?](https://www.mindstick.com/mindstickforums/50905aab-fec0-4277-a3dd-578564d3f777/images/24027672-168c-4096-a819-0fabea7a5a8c.png)

**Many to Many (M: M):-** When An entity of entity-set X can be associated with any number of entities of entity-set Y and an entity in entity-set Y can be associated with any number of entities of entity-set X.

![What is Mapping Constraints in Database Management System ?](https://www.mindstick.com/mindstickforums/50905aab-fec0-4277-a3dd-578564d3f777/images/6e2e4e8a-d471-4a6a-9b56-dae1b3f9c261.png)

AND

These relations are used in DataBaseManagement System.

\


---

Original Source: https://www.mindstick.com/forum/34816/what-is-mapping-constraints-in-database-management-system

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