E-R model:
- It is a tool for creating data model.
- It is used for developers to describe the content of data model by using two functions called entities and relationships.
Entity:
- It helps the user for tracking something in
database . - Example entities in student database system are Student, Grade, Course, etc.
Relationships:
- Entities have relationships among each other.
- For example, in student database, a Student has a relationship to Major and Student has a relationship to Advisor.
Attribute:
- It used to describe the entity characteristics.
- Example attributes of student entity is Student_id, Student_name, Student_address, etc.
Identifier:
- It is an attribute or group of attribute, but its value is related with one and only one entity instance.
Example of E-R diagram:
Explanation of Solution
Entity Relationship diagram that displays relationship among the database, database application and users:
The below is the E-R diagram that shows the relationship that is laid among the database, database application and users:
User:
The person or end user that can process the application that is stored in the database.
Database application:
A database application is a collection of four elements namely forms, reports, queries and application which acts as an intermediate between the user and data of the database
Database:
Database is a collection of information that is used to store and retrieve the data. Data is organized in tables.
Explanation of the E-R diagram:
- Many user can use the database application.
- Example of the user entity could be “students”, “faculty”.
- Many database applications can be present in a single database.
- Example of the database application could be “Bookstore”,”Library”.
- Only one database can contain many database application.
- Example of the database could be “studentDB”,”BookStoreDB”.
- The relationship between the user and the database application is “M:N (Many to many )relationship.
- The relationship between the database application and theDatbase is “N:1”(Many to One) relationship.
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