Question

Problem 1 Consider the following relations containing airline flight information, where the keys are underlined ghts(no: integer, from: string, to: string, distance: integer, departs: time, arrives: time) aircraftlaid: integer, aname: string, crusingrange: integer) certified(eid: integer,aid: integer) employees(eid: integer, ename: string, salary: integer) Note that the employees relation describes pilots and other kinds of employees as well; every pilot is certified for some aircraft (otherwise, he or she would not qualify as a pilot), and only pilots are certified to fly. Note that it is possible that some of the queries below may not be expressible in relational algebra. For such queries, informally explain why they cannot be expressed. Write the following queries in relational algebra. (5 points) a) b) Find the names of pilots certified for some Boeing aircraft. Identify the flights that are piloted by every pilot whose salary is more than 100,000. (5 points) (5 points) c) Find the eid's of employees who make the highest salary.

Answer 1

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Skp I (Aircraft Certified Employees) Joint the three tables Skp II sigma_anome = 'Boeing' (Aircraft certified Employees) Fetching aircraft name of Boeing Skp III sigma_enome (sigma_anome 'Boeing' (Aircraft certified Employees) fetching names of some pilots certified for some Boeing Aircraft soln: Pi flno (sigma_distance < earning range ^salary > 100,000 (Flights Aircraft certified employees))) Find the eid's of employees who make the highest salary The approach is to take is first find all the employees who donot have highest salary. Subtract these from the original list of employees and solve get the highest paid employees rho (E, Employees) P (E_3) Pi_E2.eid (E_1 E_1 salary > t_2 Salary E_2) rho (E_2, Employees) (pi_eid E_1) - E_3 Ans