Simple attributes are atomic values that cannot be divided further.
⇒ Example: A student's mobile number (10 digits), Birth Date (date-month-year).
Composite attributes consist of more than one simple attribute and can be divided into a tree-like structure.
Example: A student's complete name may have First_Name and Last_Name.
An address may include Street, City, State, Country, and PIN code.
Single-valued attributes contain a single value.
Example: Aadhar_card_no, Roll_no.
Multi-valued attributes may contain more than one value and are represented by a double ellipse.
Example: A person can have more than one Phone_Number, Email_Address.
Stored attributes are physically stored in the database. Most attributes are stored except a few.
Example: Roll_No, Name, Birth_Date, Phone_No.
Derived attributes are not stored in the physical database but are derived from other attributes. Derived attributes are depicted by a dashed ellipse.
Example: Age can be derived from Birth Date.
Average Salary in a department can be derived rather than stored.
A key attribute uniquely identifies each entity in the entity set. It represents a primary key and is represented by an ellipse with an underline.
Example: Roll_No will be unique for each student.
⇒ Student: (Roll_No, Name, BirthDate, Age, Address, Phone_Number)
