Database Design Fundamentals

INTRODUCTION

Databases are a collection of organized information that can easily be accessed, managed and updated. A good database results in a better system. There are two steps to designing an effective database. First is making a rough skeleton of it (ER diagram) and conversion of the skeleton to a relational schema.

WHAT IS ER DIAGRAM?

An Entity–relationship model (ER model) describes the structure of a database with the help of a diagram, which is known as Entity Relationship Diagram. There are three main components of ER diagram Entity, Relationship and attributes.

An entity can be a real-world object, either animate or inanimate, that can be easily identifiable. For example: Student, Book, Car

The association among entities is called a relationship. For example, students enroll in a course. Here enroll is a relationship between entities Student and Course.

Entities are represented by means of their properties, called attributes.

For example, Name, Roll No, Marks are attributes of entity Student.

ER diagram gives us an idea of how the final system will look like after its complete implementation. It defines the data elements and the relationships between the data elements. ER diagrams are used to show how data is stored, connected, accessed and updated in the database management system.

WHAT IS RELATIONAL MODEL

Relational Model (RM) represents the database as a collection of relations. Relational Model represents how data is stored in a database in the form of a table.

NEED OF CONVERSION OF ER DIAGRAM TO RELATIONAL SCHEMA

After designing the ER diagram of the system, we need to convert it to Relational models which can directly be implemented by any RDBMS like Oracle, MySQL etc. Rough skeleton of any database needs to be converted into relational form to make use of it.