Employee Project ER Diagram Practice Problem
(Not in textbook)
A company has a number of employees. The attributes of employee include Employee ID, name,
address, and birthdate. The company also has several projects. Attributes of project include project ID,
project name, and start date. Each employee may be assigned to one or more projects, or may not be
assigned to a project. A project must have at least one employee assigned, and may have any number of
employees assigned. The company also needs to store the total number of employees assigned to each
project. An employee’s billing rate may vary by project, and the company wishes to record the
applicable billing rate (Billing_Rate) for each employee when assigned to a particular project.
Draw an E-R Diagram based on the description above. If an attribute can be easily decomposed, please
also depict sub-component attributes.
Solution
Since an Employee can be assigned to many Projects and a Project can have many Employees, we
describe the relationship between Employee and Project as many-to-many or M:N. Billing_rate is an
attribute of the relationship between these two entities.