Applied Database Systems
Relational Algebra
Consider the following relations containing airline flight information:
Flights(flno: integer, from: string, to: string, distance: integer, departs: time, arrives: time, aid:integer)
Aircraft(aid: integer, aname: string, cruisingrange: integer)
Certified_Pilot(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. Write the following queries in relational algebra.
- Find the eids of pilots certified for some Boeing aircraft.
- Find the names of pilots certified for some Boeing aircraft.
- Find the aids of all aircraft that can be used on non-stop flights from Bonn to Madras.
- Identify the flights that can be piloted by every pilot whose salary is more than $100,000.
- Find the names of pilots who can operate planes with a range greater than 3,000 miles but are not certified on any Boeing aircraft.
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