Attributes in Entity-Relationship Model

1. Title:
Attributes in Entity-Relationship
Model

2. Entity and an Attribute
An Entity may be an object with a physical existence
or an object with a conceptual existence.
Attributes are the properties which define the entity
type. All attributes have values.
For example, a student entity may have name, class,
and age as attributes.

3. Type of Attributes
1. Atomic or Simple Attribute.
2. Composite Attribute.
3. Single Valued Attribute.
4. Multi Valued Attribute.
5. Derived Attribute.

4. Simple attribute: Simple attributes are atomic values,
which cannot be divided further.
For example, a student's phone number is an atomic
value of 8 digits.
Composite attribute: Composite attributes are made
of more than one simple attribute.
For example, a student's complete name may have first
name and last name.
Derived attribute: Derived attributes are the
attributes that do not exist in the physical database, but
their values are derived from other attributes present in
the database.
For example, Age can be derived from DOB

5. Single-value attribute: Single-value attributes
contain a single value. For example, Any
manufactured product can have only one serial no.
Multi-value attribute: Multi-value attributes may
contain more than one values. For example, a person
can have more than one phone number or email
address.

6. Entity Relationship Diagram:
Rectangle: Represents Entity sets.
Ellipses: Represents Attributes
Diamonds: Represents Relationship Set
Double Ellipses: Represents Multivalued Attributes
Dashed Ellipses: Represents Derived Attributes

7. Thanks