Question

(Please do not copy and paste from another question. I am new to this and need it to be simple)

Draw an ERD for a “Hospital” with many departments and employees in each department. show things like (one to one, one to many, many to many).

What attributes would you store regarding each objects/class/data entities?

Thank you!

(Example)

FIGURE 4-10 An ERD for a bank with many branches Customer cust number-PK name bill address home phone office phone = Account account ID-PK account type La date opened balance = Branch branch ID-PK manager name location main phone = - - - Transaction trans ID-PK trans date trans type trans amount

Answer 1

Hospital Department PK PK Hospitali name phone DepartmentID Address Phone Hospital D Location FK Employee PK Employeeld EmployeeName EmployeePhone Location DepartmentID FK

As you said you're new to this.Let me explain from the scratch
The above notation used to draw ER diagram is called Crow's foot notation and the tool used is Lucidchart
This represents an entity(table) key is PK(Primary Key) and FK(Foreign Key)

Entity Key Field Key Field Key Field

this represents a many-to-one relationship

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Let's get into Entities:

The entities are:

• Hospital
• Department
• Employee

The attributes of th entities are:

• Hospital(HospitalID,Name,Phone,location)
• Department(DepartmentID,address,phone,HospitalID)
• Employee(EmployeeID,Name,Phone,Address,DepartmentID)

The underlined are the primary keys
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Let's get into relationships between the entities:

1. A hospital can have many departments but a department belongs to only hospital(makes sense right?)
   so relationship between hospital and department is Many-to-One.
   Since a hospital can have many departments so we need to refer to our hospitalID in Department so that we can say which department belongs to which hospital.So HospitalID referred from Hospital is the foreign key for Department.
2. A Department can have many employees whereas an employee can work for only department(makes sense right?) so the relationship between employee and department is many-to-one. We need to include a foregin key departmentID in employee table so that we can know which employee belongs to which department.

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