Below is a clear, complete, and exam-oriented explanation of the Types of Attributes in the Database Conceptual Model (ER Model) —

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⭐ TYPES OF ATTRIBUTES IN DATABASE CONCEPTUAL MODEL (ER MODEL)

In an Entity–Relationship (ER) Model, attributes describe the properties or characteristics of an entity.
Different types of attributes help represent data more accurately and support correct database design.

Attributes are classified into the following major types:

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1. Simple Attribute

A simple (atomic) attribute cannot be divided into smaller parts.

✔ Has a single, indivisible value
✔ Most common type

Examples:

• Age
• Salary
• RollNo
• Gender

Symbol: Single oval

   (Age)

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2. Composite Attribute

A composite attribute can be divided into smaller sub-attributes.

✔ Useful for structured data
✔ Inner components can be individually stored

Example:
Address → House No, City, State, Pin
Name → FirstName, MiddleName, LastName

Symbol: Oval connected to smaller ovals

     (Address)
     /   |    \
(City)(State)(Pin)

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3. Single-Valued Attribute

A single-valued attribute holds only one value for an entity.

✔ Cannot store multiple values
✔ Stored as one field in a table

Examples:

• DateOfBirth
• Aadhaar Number
• Email (if only one allowed)

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4. Multi-Valued Attribute

A multi-valued attribute can hold multiple values for a single entity.

✔ Stored as a separate table in RDBMS
✔ Represented by double oval

Examples:

• Phone Numbers (Student may have 2 numbers)
• Skills (Employee may have many skills)
• Languages Known

Symbol:

((Phone))

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5. Derived Attribute

A derived attribute does not exist physically in the database; it is calculated from other attributes.

✔ Value is derived (not stored)
✔ Stored only when needed
✔ Saves storage

Examples:

• Age (derived from DateOfBirth)
• TotalPrice (Quantity × UnitPrice)
• YearsOfExperience (CURRENT_DATE – JoinDate)

Symbol: Dotted oval

(...Age...)

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6. Key Attribute

A key attribute uniquely identifies an entity.

✔ Corresponds to Primary Key in a table
✔ Underlined in ER diagrams

Examples:

• RollNo (Student)
• EmployeeID
• Aadhaar Number

Symbol:

  (RollNo)  ← underlined

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7. Composite Key Attribute

A key that consists of two or more attributes together.

✔ Used when no single attribute uniquely identifies the entity
✔ Common in bridge/associative entities

Examples:

• (StudentID, CourseID) in ENROLLMENT table
• (BookingID, RoomNo)

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8. Complex Attribute (Nested Attribute)

These are attributes that combine multi-valued + composite types.

Example:
Address may have multiple values for one customer:

• Home Address
• Office Address

Each address has composite fields (City, Pin, etc.)

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QUICK SUMMARY TABLE (Exam-Friendly)

Attribute Type	Meaning	Example	Symbol
Simple	Cannot be divided	Age, Salary	Single oval
Composite	Can be divided	Address, Name	Oval + sub-ovals
Single-valued	One value	DOB, Email	Single oval
Multi-valued	Many values	Phone, Skills	Double oval
Derived	Calculated	Age, TotalPrice	Dotted oval
Key	Unique identifier	RollNo, EmpID	Underlined
Composite key	Multi-attribute key	(RollNo, CourseID)	Underlined group
Complex	Composite + multi-valued	Multiple addresses	Hierarchical ovals

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⭐ Perfect 5-Mark Answer (Short and Crisp)

Attributes describe properties of an entity in an ER model.
Their types include:

• Simple attributes – indivisible values (Age).
• Composite attributes – composed of sub-attributes (Address → City, State).
• Single-valued attributes – only one value (DOB).
• Multi-valued attributes – multiple values (Phone Numbers).
• Derived attributes – calculated from other attributes (Age from DOB).
• Key attributes – uniquely identify an entity (RollNo).

These help designers represent real-world data accurately and create a correct database schema.

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