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Relational Algebra and SQL Examples

Relational Algebra and SQL Examples. Revised based on the notes from Dr. Shiyong Lu of Wayne State University Database Systems: An Application Oriented Approach, Edition 2 by Michael Kifer , Arthur Bernstein, Philip M. Lewis ISBN:0321268458 ISBN13:9780321268457 Release Date:March 2005.

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Relational Algebra and SQL Examples

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  1. Relational Algebra and SQL Examples Revised based on the notes from Dr. Shiyong Lu of Wayne State University Database Systems: An Application Oriented Approach, Edition 2 by Michael Kifer, Arthur Bernstein, Philip M. Lewis ISBN:0321268458 ISBN13:9780321268457 Release Date:March 2005

  2. Relational Algebra and SQL Exercises • Professor(ssn, profname, status) • Course(crscode, crsname, credits) • Taught(crsname, semester, ssn) Please refer to the SQLite commands that create the test database.

  3. Query 1 • Professor(ssn, profname, status) • Course(crscode, crsname, credits) • Taught(crsname, semester, ssn) Return those professors who have taught ‘CSCI203’ but never ‘CSCI240’.

  4. Relational Algebra Solution • Professor(ssn, profname, status) • Course(crscode, crsname, credits) • Taught(crsname, semester, ssn) ssn(crsname=‘CSCI203’(Taught)) -ssn(crsname=‘CSCI240’(Taught))

  5. SQL Solution • Professor(ssn, profname, status) • Course(crscode, crsname, credits) • Taught(crsname, semester, ssn) SELECT ssn From Taught Where crsname = ‘CSCI203’ EXCEPT SELECT ssn From Taught Where crsname = ‘CSCI240’;

  6. Query 2 • Professor(ssn, profname, status) • Course(crscode, crsname, credits) • Taught(crsname, semester, ssn) Return those professors who have taught both ‘CSCI203’ and ‘CSCI204’.

  7. Relational Algebra Solution • Professor(ssn, profname, status) • Course(crscode, crsname, credits) • Taught(crsname, semester, ssn) ssn(crsname=‘CSCI203’  crsname=‘CSCI204’ (Taught), wrong! ssn(crsname=‘CSCI203’(Taught))  ssn(crsname=‘CSCI204’(Taught)), correct!

  8. SQL Solution • Professor(ssn, profname, status) • Course(crscode, crsname, credits) • Taught(crsname, semester, ssn) SELECT T1.ssn From Taught T1, Taught T2 Where T1.crsname = ‘CSCI203’ AND T2.crsname=‘CSCI204’ AND T1.ssn=T2.ssn;

  9. Query 3 • Professor(ssn, profname, status) • Course(crscode, crsname, credits) • Taught(crsname, semester, ssn) Return those professors who have never taught ‘CSCI204’.

  10. Relational Algebra Solution • Professor(ssn, profname, status) • Course(crscode, crsname, credits) • Taught(crsname, semester, ssn) ssn(crsname<>‘CSCI204’(Taught)), wrong answer! ssn(Professor) -ssn(crsname=‘CSCI204’(Taught)), correct answer!

  11. SQL Solution • Professor(ssn, profname, status) • Course(crscode, crsname, credits) • Taught(crsname, semester, ssn) SELECT ssn From Professor EXCEPT SELECT ssn From Taught T Where T.crsname = ‘CSCI204’;

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