Answered! Given the following relational schemas of a Hospital database, express the queries using Relational Algebra. Hospital…

ans 2 :π_​Name (σ_{Doc_id=Emp_id∧salary>150k}(Doctor X Employee))

ans 3: π_{​Pt_id,Name}(σ_{new.Pt_id=Patient.Pat_id}(ῥ_new(π_{Pat_id}(σ_{Doctor.Doc_id=Sees.Doc_id∧Name=”Johnson”}(Doctor X Sees))) X Patient))

ans 4: take cross product of doctor and employee to find the female doctors and then find the patients treated by them by take cross product with sees and then find the patients which are female by taking cross product with patient.

ans 5: π_{Emp_id,Phone,DoB,Office_room,Address,Salary,Gender}(Employee) –   π_{Emp_id,Phone,DoB,Office_room,Address,Salary,Gender}(σ_{Emp_id=Doc_id}(Employee X Doctor)

ans 6: π_{Name,Area_of_Expertise(}σ_{Doctor.Doc_id=Sees.Doc_id ∧ Pat_id=”P_111000″}(DoctorXSees))

ans 7: π_Name,Gender(σ_{Patient.Pat_id=Patient_History.Pat_id ∧ Problem_Area=”Cancer”}(Patient X Patient_History))

ans 8: π_{Office_room}(σ_{name=”Smith”∧ Doc_id=Emp_id∧ Area_of_Expertise=”Diabetes & Obesity”}(Doctor X Employee))

ans 9: staff’s name is not give in the data base. but we can find doctor’s and patient’s name id and addresses by using union operation as given below :

π_{name,Address,Pat_id}(Patient) ∪ π_{Name,address,emp_id}(σ_{emp_id=doc_id}(Doctor X Employee))

to find staff’s id and address we can use π_{address,emp_id}(Employee)

ans 10: if hospital is expanded to more than one building then we can add one attribute building_id to employee to make info about the room in a particular building.