The document discusses database design and the entity-relationship model. It describes the stages of database design as requirements analysis, database designing, and implementation. It also explains the key components of the entity-relationship model including entities, attributes, keys, relationships, and notations. The entity-relationship model is a high-level data model used to define the data elements and relationships in a database system.

1. DATABASE
MANAGEMENT
SYSTEMS

2. “
…repent therefore and be converted
2
…you must be born again

3. BIG CONCEPT
The Operating system is
a resource manager
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4. Overview of Database Design
Database Design is a collection of processes that facilitate the
designing, development, implementation and maintenance of
enterprise data management systems.
• Properly designed databases are easy to maintain,
improves data consistency and are cost effective in terms
of disk storage space.
• The database designer decides how the data elements
correlate and what data must be stored.
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5. Stages of Database Design
Three stages of Database Design
• Requirements Analysis: involves planning and system definition
• Database Designing: using models to represent the database.
• Implementation: implementing your created model on an
actual DBMS and making sure it works.
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6. Database Design Models
• The main objectives of database design is to produce design
models of the proposed database system.
The logical model concentrates on
• the data requirements and the data to be stored.
It does not consider
• The physical database: how the data will be stored or where
it will be stored physically.
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7. Database Design Models
The physical data design model
• The logical DB design of the database is translated onto a
physical media
• Uses hardware resources and software systems such as
database management systems (DBMS).
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8. The Logical Model
Examples include:
• Hierarchical database model
• Relational model
• Network model
• Object-oriented database model
• Entity-relationship model 8

9. Entity-relationship model
• ER model stands for an Entity-Relationship model. It is a high-
level data model. This model is used to define the data
elements and relationship for a specified system.
• It develops a conceptual design for the database. It also
develops a very simple and easy to design view of data.
• In ER modeling, the database structure is portrayed as a
diagram called an entity-relationship diagram.
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10. Component of ER Diagram
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11. Entity-relationship model
• An entity is a representation of a real object, class, person or
place. In the ER diagram, an entity can be represented as
rectangles.
• Consider an organization as an example- manager, product,
employee, department etc. can be taken as an entity.
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12. Entity-relationship model
Weak Entity
• An entity that depends on another entity called a weak
entity. The weak entity doesn't contain any key attribute of
its own. The weak entity is represented by a double
rectangle.
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13. Entity-relationship model
Attribute
• The attribute is used to
describe the property of an
entity. Eclipse is used to
represent an attribute.
• For example, id, age, contact
number, name, etc. can be
attributes of a student.
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14. Entity-relationship model
Key Attribute:
• represents an attribute or
group of attributes whose
values can be used to
uniquely identify an
individual entity.
• It is represented by an
underlined text
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15. Entity-relationship model
Primary key:
• The primary key is a candidate key
that is to be used as an identifying
mechanism for the entity.
• It must uniquely identify tuples in a
table and not be null. The primary
key is indicated in the ER model by
underlining the attribute.
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16. Entity-relationship model
Foreign key (FK) :
• An attribute in a table that references the primary key in another
table and can be null.
• Both foreign and primary keys must be of the same data type.
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17. Entity-relationship model
Composite Attribute:
• An attribute that is composed
of many other attributes.
• It is represented by an ellipse,
which is connected with other
ellipses.
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18. Entity-relationship model
Multivalued Attribute:
• An attribute that have more than one value.
• The double oval is used to represent multivalued attribute.
• For example, a student can have more than one phone
number.
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19. Entity-relationship model
Derived Attribute:
• An attribute that can be derived
from other attribute.
• Represented by a dashed ellipse.
• Example: person's age. It changes
over time and can be derived
from another attribute like Date
of birth.
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20. Entity-relationship model
Relationship:
• A relationship is used to describe the relation between entities.
• Diamond or rhombus is used to represent the relationship.
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21. Entity-relationship model
Types of relationship are as follows::
One-to-One Relationship
• When only one instance of an entity is associated with the
relationship, then it is known as one to one relationship.
• For example, A female can marry one male, and a male can
marry one female.
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22. Entity-relationship model
Types of relationship are as follows::
One-to-One Relationship
• When only one entity relates to only one other entity.
• For example, A female can marry one male, and a male can
marry one female.
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23. Entity-relationship model
Types of relationship are as follows::
One-to-Many Relationship
• When only one entity relates to more than one entity.
• For example: a scientist can invent many inventions, but the
invention is done by the only specific scientist.
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24. Entity-relationship model
Types of relationship
• Many-to-One Relationship
• Many-to-Many
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25. Notations of ER Model
• A database can be
represented using the
notations.
• In ER model, many
notations are used to
express the cardinality.
These notations are as
follows:
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