Page 245 - Touhpad Ai

Types of Data Models
As the need to store and use data has grown, different types of data models have been developed. Each type is used in
different situations depending on the kind of data and how it is used.

Hierarchical Data Model
In the Hierarchical data model, data is stored in a tree-like structure, where one main item (called the parent) is linked
to many others (called children). In the hierarchical model, each parent can have many children, but each child has only
one parent.
Example: Think of a school. The principal is the parent, and under them are teachers (children). Each teacher can have
multiple students, but each student belongs to only one teacher.
This model was used in old systems like IBM’s IMS and is still used in some places like XML files and geographic systems
(GIS). However, it's not as flexible as modern models.

Relational Data Model

In this model, data is stored in tables (also called relations). Tables in a relational data model are connected using a
common field, like an ID. Each table has rows and columns. This model helps keep data organised and reduces repetition.
Example: One table stores student data:

Student_ID Name Class
101 Sonia 11A

102 Parul 11B

Another table stores exam scores:

Student_ID Subject Marks
101 Maths 88
102 Science 90

We can connect these two tables using the Student_ID.
Relational databases use SQL (Structured Query Language) and are widely used in shopping systems, banking, and
schools because they keep data organised and avoid repetition. It is often used to manage and query data in relational
databases.

Entity-Relationship (ER) Model
This model uses diagrams to show how data items (called entities) are related to each other.

Example: An ER diagram might show that:
u A Student enrolls in a Course
u A Teacher teaches the Course

Teacher Teaches Student

Teacher Student

Teacher_ID Student_ID
Name Entities Name Entities
Subject Class

Data Modelling and Simple Linear Regression 243