A thing in the world with independent existence.
Maybe an object with physical existence (house, person) or conceptual existence(course, job)

They are properties that describe entities

Example - An entity “PERSON” can have attributes like name, age, phone no., address

Composite attributes - Can be divided further. ex - Name , firstName, middleName, lastName

Simple attributes - Can not be divided further. ex - weight

Single-valued attributes - have single value for particular entity ex - Age

Multi-valued attributes - have multiple values ex - College Degree

Derived attributes - Can be derived from other attributes ex- Age can be derived from DOB

Stored Attributes - From which values of other attributes are derived ex- DOB can help derive Age

Complex Attributes - Has multi values and composite elements in it.

Multivalued attributes → represented within ‘{ }’.
Composite attributes → represented within ‘( )’.

Ex: {CollegeDegrees (College, YEAR, Field)}

NULL Values - Null is something which is not applicable or unknown.

ENTITY TYPES : Collection of entities that have same attributes.
Ex: Student

ENTITY SET : Collection of entities of a particular entity type at a point in time.

Ex: Students between age 20-23 } This is set of specific age groups.

Key attribute- The attribute that is able to identify each entity uniquely.
Ex: Roll number of student

Entity Relationship model in DBMS