Statements I, II, III, IV, V, VII, and VIII are true, while statement VI is false.
What validate these sentences?
I) A managee can have many managers.
- True. This is reflected in the diagram by the "Manages" relationship between Employee and Manager.
II) An employee may not manage anyone.
- True. The "Manages" relationship is optional, indicated by the crow's foot (partial participation) on the Employee side.
III) An employee can be both a manager and a managee at the same time.
- True. The diagram allows for an employee to have both roles through the "Manages" relationship.
IV) Manages is a binary relationship because there are two roles involved.
- True. A binary relationship involves two roles, and in this case, it's between Employee and Manager.
V) Not every employee is managed by someone.
- True. The "Manages" relationship is optional on the Employee side, meaning not every employee needs to be managed.
VI) An employee must manage multiple employees.
- False. The diagram allows an employee to manage zero or more employees, so it's not required to manage multiple employees.
VII) The boss can be an employee and be identified in the resulting table.
- True. The diagram allows for a manager to also be an employee, and this is represented in the "Manages" relationship.
VIII) The ER diagram can be converted into one table, and created using the SQL below:
create table employee (
EmpID integer not null,
MgrID integer,
primary key (EmpID),
foreign key (MgrID) references employee (EmpID)
);
- True. The SQL statement given shows a table with an employee ID and a manager ID, where the manager ID is a foreign key referencing the employee table.
As a result, statements I, II, III, IV, V, VII, and VIII are true, while statement VI is false.