Entity relationship diagram is a visual database development tool which presents the relationship between the entities in a data base in a visual form. Entity relationship diagram plays a significant role in database system development since it outlines the structure of the database in a simple format. It shows the connection between the entities within the database, the attributes of each entity and the level of cardinality between the entities. It is a graphical representation of the relationship of entities and attributes in a database system. Entity relationship diagram can be used as a data modeling technique that aid in defining business processes and a foundation of relational database (Paredaens, Jan, et al. 34).
ERD is employed in the database presented to outline the entities and attributes as well as the relationship that exist among them in a graphical format. It will present a deeper and a simpler understanding of the foundation of the database presented. First, it is imperative to identify all the entities used in the presented database. After the entities have been identified, all the attributes of each entity should be outlined. It is also significant to identify the primary keys in each table or attribute in the database. Primary keys are very important in outlining the relationship that exist between one or more tables or attributes within a database. Also, the foreign key should be identified and marked. Primary key is the unique attribute used to identify a given entity or table. On the other hand, a foreign key is a shared primary key of a given entity but not a primary key in another entity.
Entities and Attributes
The presented database has the following entities: Assignment, computer, computer assignment, department, employee and project. The entities have different attributes as shown below:
Computer: SerialNumber, Make, Model, ProcessorType, ProcessorSpeed, MainMemory and DiskSize. The primary key for this entity will be the SerialNumber.
Employee: EmployeeNumber, FirstName, LastName, Department, Phone and Email. The primary key is the EmployeeNumber.
Project: ProjectID, ProjectName, Department, Maxhours, StartDate and EndDate. The primary key is ProjectID.
ComputerAssignment: SerailNumber, EmployeeNumber and DateAssigned.
Relationship
Employees are assigned computers to perform different projects. An employee belongs to a department. Computer assignment is used to shown the relationship between employee and the computers.
Employee belongs to a Department
Employee is assigned a Computer
Employee performs a Project
Cardinality
ERD
Works Cited
Paredaens, Jan, et al. The structure of the relational database model. Vol. 17. Springer Science
& Business Media, 2012.
