Data Modelling

Question 1

What is Data Modeling?

Answer 1

The process of creating a visual representation of data and its relationships in a system to support database design and business requirements.

Purpose: Organize data logically, reduce redundancy, support accurate data storage and retrieval.

Question 2

Define Conceptual Data Model.

Answer 2

A high-level, abstract representation of organizational data, focusing on business concepts and rules rather than technical details.

Characteristics: Shows entities and relationships, no technical or database implementation details, used for understanding business requirements.

Question 3

What are the entities in a Conceptual Data Model example?

Answer 3

• Customer
• Order
• Product

Relationship: Customer places Order; Order contains Product.

Question 4

Define Logical Data Model.

Answer 4

A detailed representation of data requirements, independent of physical database structure, focusing on attributes, keys, and relationships.

Characteristics: Defines entities, attributes, primary keys, and foreign keys.

Question 5

What is the primary key for the Customer entity in a Logical Data Model?

Answer 5

Customer_ID

Example: Customer (Customer_ID, Name, DOB).

Question 6

What is the difference in purpose between Conceptual and Logical Models?

Answer 6

• Conceptual Model: Understand business requirements
• Logical Model: Define data structure in detail

Detail Level: Conceptual is high-level, Logical is medium-level.

Question 7

True or false: The Logical Model is DBMS-independent.

Answer 7

TRUE

However, it is more structured compared to the Conceptual Model.

Question 8

What is the audience for the Conceptual Model?

Answer 8

Business stakeholders

The Logical Model is aimed at data architects and developers.

Question 9

What is the summary of the three types of data models?

Answer 9

• Conceptual Model: Focus on business entities and relationships
• Logical Model: Focus on attributes, keys, and constraints without worrying about the database
• Physical Model: Focus on DBMS-specific implementation

Always start with conceptual → logical → physical.

Question 10

What does an ER diagram represent?

Answer 10

Used for conceptual and logical modeling

It visually depicts entities and their relationships.

Question 11

What SQL command is used to create the Customer table?

Answer 11

CREATE TABLE Customer (
Customer_ID INT PRIMARY KEY,
Name VARCHAR(50),
DOB DATE
);

This is part of the Logical Model with attributes and keys.

Question 12

What is the primary key in the Order_Product table?

Answer 12

PRIMARY KEY (Order_ID, Product_ID)

This table establishes a many-to-many relationship between Orders and Products.

Question 13

What is the main part in the design of a database?

Answer 13

the creation of a data model

This step culminates in a graphical representation of entities and records for the database schema.

Question 14

What is the best-known way to create a data model?

Answer 14

Entity-Relationship Diagram (ERD)

The Entity-Relationship model is a structured way of data modeling for relational databases.

Question 15

True or false: Changing the data model as you go along is easy and requires little work.

Answer 15

FALSE

Changing the data model usually requires a lot of work, especially in relational databases.

Question 16

What are the three design phases recommended for database design?

Answer 16

• Conceptual
• Logical
• Physical

These phases help manage the design process effectively.

Question 17

In the Conceptual phase, what do we map out?

Answer 17

main entities, relationships, and attributes

This phase does not consider how to store them in the database yet.

Question 18

During the Logical phase, what do we decide regarding entities and relationships?

Answer 18

which will be stored in a relational database

Each entity is associated with a table containing attributes as columns.

Question 19

What does the Physical phase determine?

Answer 19

how each table should be stored in a computer

This phase relies on familiarity with the specific database management system.

Question 20

What is the consequence of changing the data structure mid-way through development?

Answer 20

requires rewriting many lines of code

All code relies on the initial data structure created.

Question 21

What is a critical step before embarking on any new application that requires a database?

Answer 21

build your data model structure or ERD

This preparation is essential for effective database design.

Question 22

What is the difference between relational and non-relational databases?

Answer 22

relational databases have a well-defined, rigid structure

Non-relational databases offer more flexibility in data storage.