Logical Data Modeling – Manager/ Employee Relationships
You are modeling the relationship of employees and managers in your organization. One possibility is to show a unary or recursive relationship on the EMPLOYEE entity. How would you model the cardinality of the unary relationship to indicate that an employee has one manager and a manager may have many employees? Draw the model to show that an employee must have a manager. Now draw the model to show that a manager must have at least one employee. What happens if a manager has only one employee assigned, and then that employee is reassigned? Draw the relationship with cardinalities to indicate that a manager may have no employees.
Your organization asks you to create a data model for employees participating in projects. One employee can participate in many projects. One project can have many employees assigned. Your stakeholders want to know the role of each employee on a project. Address the following questions in your paper:
Which type of entity will help you model this many-to-many relationship?
Is it possible for a project to have no employees assigned, and how would you model that possibility?
Is it possible for an employee to be unassigned to any project, and how would you model that possibility?