E-R model (Entity-Relationship model) in DBMS, Attributes

 E-R Model (Entity-Relationship Model) :-

• It a  high level conceptual data model. 
• It allows us to describe the data involved in a real world inter price , in terms of objects & there relationship. It is validly used to developed an initial design of data base it provides a set of useful concepts that make it convenient for a developer.
• It describes data as a collection of entities relationship & attributes.

Entities:-

An entities is an object of consult used to represent the things in the real word. Eg:- Car, Table, etc.

An entity need not be a physical entity it can also represent a concept in real words. Eg:- Project, Loan, etc.

Entity Set:-

A collection of similar kind of entities is called an entity set all entity type -> In college  database students, faculty, Course & Department are consort of check.

The collection of all the students similarly collection of all course from an entity set course.

Entity Identifier key attributes:-

An entity type usually has an attribute whose value are distinct for each individual entity in the collection. such an attributes is called a key attributes & its values can be used to identity each entity uniquely.

Strong Entities:- 

The entity types containing a key attributes are called strong entity type an regular entity type.

Attributes:- 

It is a property used to describe the specific feature of the entity, so to describe an entity entirely a set of attributes is used.

Ex:- A student entity may be describe by the student name, age, address, course, etc.

An entity will have a value for each of its attributes, Ex:- student entity will have

Name- xyz

Course- abc

Address- ............

Roll no.- 123

Domain:- 

Each simple attributes of an entity type contains a possible set of values that can be attached to it. This is called the domain of attributes, an attributes can not contain a value outside this domain.