ER diagram notation in DBMS Theory - Mini Project: Build & Apply

Understanding ER Diagram Notation

📖 Scenario: You are designing a simple database for a library. You want to represent the main parts of the system using an Entity-Relationship (ER) diagram. This diagram will help you understand how different pieces of information relate to each other.

🎯 Goal: Build a basic ER diagram notation using text descriptions for entities, attributes, and relationships. You will create the main entities, define their attributes, set a key attribute, and describe the relationship between entities.

📋 What You'll Learn

Create entities with their exact names

List attributes for each entity with the exact names

Mark the primary key attribute for each entity

Define the relationship between entities with the exact name

Specify the cardinality of the relationship

💡 Why This Matters

🌍 Real World

ER diagrams are used to plan and design databases by visually showing how data is organized and connected.

💼 Career

Database designers, developers, and analysts use ER diagrams to communicate database structure clearly before implementation.

1

Create Entities with Attributes

Create two entities called Book and Author. For Book, add attributes BookID, Title, and Genre. For Author, add attributes AuthorID, Name, and Country.

DBMS Theory

# Define entities Book and Author with their attributes
# Your code here

Need a hint?

Think of entities as objects and attributes as their properties. Use dictionaries to represent each entity with a list of attributes.

2

Mark Primary Keys

Add a key called primary_key to each entity dictionary. Set BookID as the primary key for Book and AuthorID as the primary key for Author.

DBMS Theory

Book = {
    'attributes': ['BookID', 'Title', 'Genre']
}

Author = {
    'attributes': ['AuthorID', 'Name', 'Country']
}
# Add primary_key to each entity
# Your code here

Need a hint?

The primary key uniquely identifies each record in an entity. Add it as a separate key in the dictionary.

3

Define Relationship Between Entities

Create a dictionary called Writes to represent the relationship between Author and Book. Include keys entities with the list ['Author', 'Book'] and relationship_type with the value one-to-many.

DBMS Theory

Book = {
    'attributes': ['BookID', 'Title', 'Genre'],
    'primary_key': 'BookID'
}

Author = {
    'attributes': ['AuthorID', 'Name', 'Country'],
    'primary_key': 'AuthorID'
}
# Define Writes relationship
# Your code here

Need a hint?

The relationship dictionary shows which entities are connected and how many instances relate to each other.

4

Complete ER Diagram Notation Summary

Create a dictionary called ER_Diagram that includes the keys entities with the list [Book, Author] and relationships with the list [Writes].

DBMS Theory

Book = {
    'attributes': ['BookID', 'Title', 'Genre'],
    'primary_key': 'BookID'
}

Author = {
    'attributes': ['AuthorID', 'Name', 'Country'],
    'primary_key': 'AuthorID'
}

Writes = {
    'entities': ['Author', 'Book'],
    'relationship_type': 'one-to-many'
}
# Combine entities and relationships into ER_Diagram
# Your code here

Need a hint?

This final dictionary summarizes the ER diagram by grouping all entities and relationships together.