Learn basic database concepts and techniques used to design and work with databases.

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To start, we will learn about the various database systems and structured query language (SQL) from scratch. Then, this module will introduce us to the different concepts and techniques that are used in designing a database management system, such as ER data models and relational data models. We will also learn about relational databases and familiarize ourselves with important ideas such as keys, constraints, and operations regarding relational databases. At the end of this module, we’ll learn about two other key concepts in database design, namely normalization and functional dependencies.

Database Design Fundamentals for Software Engineers

## Relationships, relationship sets and relationship types

A relationship is an association between two entities, for example, an entity EMPLOYEE WORKS_ON PROJECT, which is another entity. However, note that different instances of employees will be working on different projects. So an employee, John WORKS_ON Project Netlife and maybe some other employee Sara (who is also an instance of an employee) WORKS_ON Project mForm. 

So we can say that **relationship type** is simply the relationship that exists between two entities like WORKS_ON. While the set of similar associations at a point of time is called the **Relationship Set**.

The illustration below will help clear up  the confusion:


# Relationships, relationship sets and relationship types

A relationship is an association between two entities, for example, an entity EMPLOYEE WORKS_ON PROJECT, which is another entity. However, note that different instances of employees will be working on different projects. So an employee, John WORKS_ON Project Netlife and maybe some other employee Sara (who is also an instance of an employee) WORKS_ON Project mForm. 

So we can say that **relationship type** is simply the relationship that exists between two entities like WORKS_ON. While the set of similar associations at a point of time is called the **Relationship Set**.

The illustration below will help clear up  the confusion:


In this lesson, we will study the basics of relationships between entities.


Introduction

Fundamental Concepts

Data Modeling

Entity-Relationship Data Model

The Relational Data Model

Functional Dependenices

Normalization

Conclusion

Relationships, Relationship Sets and Relationship Types

Relationships, relationship sets and relationship types