4. INTRODUCTION
• Data Model defines how data is connected to each other and how they are
process and stored inside the system.
• Data Model gives an idea that how the final system look like after its
complete impletation
• The Relational Model, which uses a table-based format, is the most
common Database Model.
• Data Models are used to show how data is stored, connected ,
accesed and updated in the data management system.
5. Types of Database Models
• Relational Database Model
• Hierarchial Database Model
• Network Database Model
• Entity Relational Database Model
6. Hierarchial Database Model
* developed by IBM, in the 1950s.
* The Hierarchical Model was the first database management
system model.
* This concept uses a hierarchical tree structure to organise the data.
• The data is organized into a tree-like structure where each record
consists of one parent record and many children.
* The Hierarchy starts from the root data and then its extends the
form of a tree adding child notes to the parents notes.
8. Features
• 1. Parent-Child Relationship.
• 2. One-to-many Relationship.
• 3. Deletion Problem.
• 4. If a Parent node is related then child node is
automatically deleted.
9. Advantages
• simple hierarchical database structure.
• It has data sharing as all data are held in a
common database data and therefore sharing of
data becomes practical.
• Any changes in the parent node is automatically
reflected in the child node so integrity of the
data is maintain.
10. Disadvantages
• 1. it is quite complex to implement.
• 2.This model also lacks flexibility as the changes
in the new tables or segments often yield very
complex system management tasks.
11. Relational Database Model
• Relational Model was proposed by E.F. Codd to
model data in the form of relations or tables.
• A relational database stores data in the form of
relations (tables).
12. IMPORTANT TERMINOLOGIES
• Attribute: Attributes are the properties that define a relation.
e.g.; ROLL_NO, NAME
• Tuple: Each row in the relation is known as tuple.
• Column: Column represents the set of values for a particular
attribute..
13.
14. Network Model
• The Network Model in DBMS is a hierarchical model that is used
to represent the many-to-many relationship among the database.
• It is represented in the form of a graph hence it is a simple and easy-
to-construct database model.
• An entity can have various parents.
• All the entities are interconnected with each other as a connected
network.
16. EntityRelational DatabaseModel
• ER model stands for an Entity-Relationship model.
• Entity relationship (ER) models are based on the
real-world entities and their relationships.
• 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 (ER Diagram).
17.
18. An ER diagram has three main components:
1. Entity
2. Attribute
3. Relationship
19. 1. Entity
• An Entity is a real word think
• An entity is represented as rectangle in an ER
diagram.
Example – Student, College.
20. 2. Attribute
• An attribute describes the property of an entity.
• An attribute is represented as Oval in an ER diagram.
• There are four types of attributes:
1. Key attribute
2. Composite attribute
3. Multivalued attribute
4. Derived attribute
21. 3. Relationship
• A relationship is represented by diamond shape in ER
diagram, it shows the relationship among entities.
• There are four types of relationships:
1. One to One
2. One to Many
3. Many to One
4. Many to Many
