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Unformatted text preview: Relational Algebra and Calculus 37 Exercise 4.5 Consider the following relations containing airline ight information: Flights( no: integer , from: string , to: string , distance: integer , departs: time , arrives: time ) Aircraft( aid: integer , aname: string , cruisingrange: 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 y. Write the following queries in relational algebra, tuple relational calculus, and domain relational calculus. Note that some of these queries may not be expressible in relational algebra (and, therefore, also not expressible in tuple and domain relational calculus)! For such queries, informally explain why they cannot be expressed. (See the exercises at the end of Chapter 5 for additional queries over the airline schema.) 1. Find the eid s of pilots certified for some Boeing aircraft....
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This note was uploaded on 01/17/2012 for the course EGN 4302 taught by Professor Dr.vishak during the Fall '12 term at University of Central Florida.
- Fall '12