Creating an ER Diagram for Employee Management System PDF

306 Creating an ER Diagram for Employee Management System An Entity-Relationship (ER) diagram is a graphical representation of entities, their ** ** attributes, and the relationships between them in a database. In this lesson,...

306 Creating an ER Diagram for Employee Management System An Entity-Relationship (ER) diagram is a graphical representation of entities, their ** ** attributes, and the relationships between them in a database. In this lesson, we will explain the process of creating an ER Diagram by using an Employee ==* ** ***== * ** Management System as an example. ** * In this lesson, we will analyze the provided requirements and * * * gradually build the diagram step by step. * * The requirements describe the key components of the system, including entities, attributes, ** ** ** ** ** ** and relationships, which we will translate into a final ER Diagram. ** ** ** ** * * Requirements for the Employee Management System * 1. Record the information of each Employee. * ` ` * 2. Record the information of each Payroll. * ` ` * 3. Each Employee should receive the Payroll. * ` ` ` ` * 4. Each Employee must be associated with a unique Payroll record. * ` ` ** ** ` ` * * Steps to Create an ER Diagram * ** ** Step 1: Identify Entities *~ ~* The first step in creating an ER Diagram is to identify the main entities in the system. ** ** ==* ** ** *== * == Entities represent real-world objects or concepts for which data needs to be stored. ** **== * In this Employee Management System, the primary entities are: ** ** ** ` Employee : Represents individual employees within the organization. ` ** ** ` Payroll : Represents payroll information associated with each employee. ` ** Step 2: ~Define Attributes for Each Entity~ * * * Each entity should have specific attributes that describe its properties. * * Attributes are represented as ellipses connected to their respective entities. ** *** == ` Employee Entity ` == The Employee entity includes the following attributes: ` ` ** ` Employee_ID : A unique identifier for each Employee. This acts as a key attribute. ` ** * * *** *** ** ` Full_Name : A composite attribute composed of ` ** *** *** ` First_Name , ` ` Middle_Initial , and ` ` Last_Name. ` ** ` Birthdate : A simple attribute representing the employee’s date of birth. ` ** ** ` Gender : Specifies the gender of the employee. ` ** ** ` Address : Stores the address of the employee. ` ** ** ` Position : The job position or title held by the employee. ` ** ** ` Contact_Number : Attributes that allow an employee to have multiple contact numbers. ` ** * * ** ` Age : A derived attribute, calculated based on the Birthdate. ` ** == ` Payroll Entity ` == The Payroll entity includes the following attributes: ** ` Payroll_ID : A unique identifier for each Payroll table. This acts as a key attribute. ` ** *** *** *** *** ** ` Monthly_Salary : A attribute that indicates the employee's monthly salary. ` ** ** ` Cash_Advance : Represents any cash advances taken by the employee. ` ** ** ` Net_Pay : A derived attribute that indicates the net pay after deductions. ` ** *** *** * * ** ` Tax : Attributes representing total taxes that apply to the payroll. ` ** Step 3: Establish Relationships Between Entities ~ * * ~ Next, we identify relationships between the entities and define the type of relationship. In * * * ** *** the ER diagram, relationships are represented by diamonds connecting the related entities. *** *** ** ` Receives : The Employee entity has a one-to-one relationship with the Payroll ` ** ` ` ** ** ` ` entity, represented by the receives relationship. ` ` * This indicates that * * each employee has a unique payroll record, and ** ** * * each payroll entry is associated with only one employee. ** ** * Step 4: Define the Degree of Relationship ~ * * ~ The degree of relationship between Employee and Payroll is One-To-One (1:1), as each ` ` ` ` ** ** employee is linked to a single payroll record, and each payroll record corresponds to only one employee. This constraint is indicated by "1" on both ends of the receives relationship. ** ** Step 5: Represent Derived and Multivalued Attributes ~ ~ In ER Diagrams, special types of attributes are indicated by distinct symbols: ** ** *** Derived Attributes: Attributes like Age , Monthly_Salary , and Net_Pay are derived * ** ` ` ` ` ` ` attributes. They are shown with dashed ellipses, indicating that they are calculated from *** *** other attributes rather than stored directly in the database. *** Multivalued Attributes: Attributes like Contact_Number for Employee is multivalued, * ** ` ` meaning it can hold multiple values. It is shown as double ellipses in the ER Diagram. *** *** ** ** In the Practical Projects lesson, you will learn to create complex ER Diagrams. ** ** ** **