#datamodel #dbms #gate2021
Data model in DBMS: What are data models in dbms?What are the different categories of Data Models?
Examples of Data Models.
What are Data models?
Data Model is a collection of concept to describe the structure of a database.
Most data models also include a set of basic operations for specifying data retrieval and data updating.
Categories of Data Models:There are 3 Categories of Data Models:
1.Highlevel (conceptual) data model
2. Lowlevel (Physical) data model
3. Representational(Implementation) data model

What is High Level Data Model?
High Level Data models or conceptual data model provide concepts that are close to the way many users perceive data.
Conceptual data model uses concepts like entity, relation and attributes to describe the data model.
Describing the structure of a database such that even a kid or a lay man would understand it easily.
Low level Data model
Low level data model or physical data model describes how the data is stored on the physical storage.
Low level data model is not for common end user.
Physical data model is for computer specialist.
Representational data model:
Representational data model is an intermediate type of data model between the two extreme data model.
Representational data model is also called implementation data model because it is neither so difficult to understand for the end user nor at the same time it is not far from how the data is stored on the computer storage.
Representational data model hide details of data storage disk, but can be implemented on a computer directly.
What are we going to learn?
Categories of data models.
Types of data models

Categories of data models
There are 3 main categories of data models in which we can categorize data models.
High level or conceptual data model
Low level or physical data model
Representational or implementation data models
Types of data models
EntityRelationship model
relational data model
Network model
Hierarchical model


Categories of data models
EntityRelationship model
In entity relation data model, an entity represents a real world object or concept such as an employee or a student.
Every entity has its characteristics, which are represented as attributes.
The connection between different entities are represented with relations.

Example
Lets say we have two entities:
Employee and project
These two entities are represented like this:

Relational data model
Relational data model uses the concepts of database as a collection of tables, where each table can be stored separately as a file.
All the database operations are done with relations between the tables.
Most relational databases use high level language like SQL.
Example
Example
Hierarchical data model
Hierarchical data model organises data in a tree like structure.
Let’s say, we have a company and that company has multiple departments. Each department has multiple employees.
But one important factor of Hierarchical data model is that each child node will have a single parent node.
Example
Network data model
Network data model is like a graph and the difference between the Hierarchical data model and Network data model is that in Network data model, a child node can have multiple parent node.
Example