Relational Algebra

Q1. Select all employees who work in the IT department.

• a) σ(Department = 'IT')(Employees)

• b) π(Department = 'IT')(Employees)

• c) σ(Department == 'IT')(Employees)

• d) π(Department == 'IT')(Employees)

Q2. Retrieve only the FirstName and LastName of employees from the table.

• a) π(FirstName, LastName)(Employees)

• b) σ(FirstName, LastName)(Employees)

• c) π(EmployeeID, FirstName, LastName)(Employees)

• d) π(FirstName, Department)(Employees)

Q3. Find all employees who work in the same department and have the same salary.

• a) Employees ⋈ (Employees.Department = Employees.Department) ⋀ (Employees.Salary = Employees.Salary)

• b) Employees ⋈ (Employees.Department == Employees.Department) ⋀ (Employees.Salary == Employees.Salary)

• c) Employees ⋈ (Department = Department) ⋀ (Salary = Salary)

• d) Employees ⋈ (Department == Department) ⋀ (Salary == Salary)

Q4. Find the employees who work in the HR department but not in the Sales department.

• a) π(FirstName, LastName, Department) (σ(Department = 'HR')(Employees)) ∩ π(FirstName, LastName, Department)(σ(Department = 'Sales')(Employees))

• b) π(FirstName, LastName, Department) (σ(Department = 'HR')(Employees)) - π(FirstName, LastName, Department)(σ(Department = 'Sales')(Employees))

• c) π(FirstName, LastName, Department) (σ(Department = 'HR')(Employees)) ∪ π(FirstName, LastName, Department)(σ(Department = 'Sales')(Employees))

• d) π(FirstName, LastName, Department) (σ(Department = 'HR')(Employees)) ⋈ π(FirstName, LastName, Department)(σ(Department = 'Sales')(Employees))

Q5. Find all unique departments represented in the Employees table.

• a) π(Department)(Employees) ∩ π(Department)(Employees)

• b) π(Department)(Employees) + π(Department)(Employees)

• c) π(Department)(Employees) ⋈ π(Department)(Employees)

• d) π(Department)(Employees) ∪ π(Department)(Employees)

Q6. Find the departments that have both Managers and Analysts.

• a) π(Department)(σ(Position = 'Manager')(Employees)) + π(Department)(σ(Position = 'Analyst')(Employees))

• b) π(Department)(σ(Position = 'Manager')(Employees)) ∪ π(Department)(σ(Position = 'Analyst')(Employees))

• c) π(Department)(σ(Position = 'Manager')(Employees)) ∩ π(Department)(σ(Position = 'Analyst')(Employees))

• d) π(Department)(σ(Position = 'Manager')(Employees)) - π(Department)(σ(Position = 'Analyst')(Employees))

Q7. Select employees who earn more than $55,000 and work in the Marketing department.

• a) σ(Salary > 55000 ∧ Department = 'Marketing')(Employees)

• b) σ(Salary > 55000 ∨ Department = 'Marketing')(Employees)

• c) σ(Salary > 55000)(Employees) ∩ σ(Department = 'Marketing')(Employees)

• d) σ(Salary > 55000)(Employees) ⋈ σ(Department = 'Marketing')(Employees)

Q8. Retrieve only the EmployeeID and Salary of employees who work in the Sales department.

• a) π(EmployeeID, Salary)(σ(Department = 'Sales')(Employees))

• b) π(FirstName, Salary)(σ(Department = 'Sales')(Employees))

• c) π(EmployeeID, Salary)(σ(Department == 'Sales')(Employees))

• d) π(EmployeeID, Salary)(σ(Department = 'Sales') ⋈ Employees)

Q9. Find all employees and their corresponding department names. If an employee's department is not specified, the department name should be "Unknown."

• a) Employees ⋈ Department

• b) Employees ⋈ Department (Employees.Department == Department.Department)

• c) Employees ⋈ Department (Employees.Department = Department.Department)

• d) Employees ⋈ Department (Employees.Department == Department.Department) ∪ Employees

Q10. Find employees who work either in the IT department or the Marketing department but not in both.

• a) σ(Department = 'IT')(Employees) - σ(Department = 'Marketing')(Employees)

• b) σ(Department = 'IT')(Employees) ∩ σ(Department = 'Marketing')(Employees)

• c) σ(Department = 'IT')(Employees) + σ(Department = 'Marketing')(Employees)

• d) σ(Department = 'IT')(Employees) ⋈ σ(Department = 'Marketing')(Employees)