Chapter 5 Relational Algebra and SQL[第5章关系代数和SQL](PPT-140).pptVIP

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Chapter 5 Relational Algebra and SQL[第5章关系代数和SQL](PPT-140).ppt

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Chapter 5 Relational Algebra and SQL[第5章关系代数和SQL](PPT-140)

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Query 22 List those professors who have not taught any course in the past three semesters (F2006, W2007, F2007). SQL Solution SELECT * FROM Professor P WHERE NOT EXISTS( SELECT * FROM Taught WHERE P.ssn = T.ssn AND (T.semester = ‘F2006’ OR T.semester = ‘W2007’ OR T.semester=‘F2007’)) ) Query 23 List the names of those courses that professor Smith have never taught. Relational Algebra Solution ?crsname(Course)-?crsname(?profname=‘Smith’(Professor) (Taught) Course) SQL Solution SELECT crsname FROM Course C WHERE NOT EXISTS SELECT * FROM Professor P, Taught T WHERE P.profname=‘Smith’ AND P.ssn = T.ssn AND T.crscode = C.crscode ) Query 24 Return those courses that have been taught by all professors. Relational Algebra Solution ?crscode, ssn(Taught)/ ?ssn(Professor) SQL Solution SELECT crscode FROM Taught T1 WHERE NOT EXISTS( (SELECT ssn FROM Professor) EXCEPT (SELECT ssn FROM Taught T2 WHERE T2.crscode = T1.crscode) ) Query 25 Return those courses that have been taught in all semesters. Relational Algebra Solution ?crscode, semester(Taught)/ ?semester(Taught) SQL Solution SELECT crscode FROM Taught T1 WHERE NOT EXISTS( (SELECT semester FROM Taught) EXCEPT (SELECT semester FROM Taught T2 WHERE T2.crscode = T1.crscode) ) Query 25 Return those courses that have been taught ONLY by junior professors. Relational Algebra Solution ?crscode(Course) - ?crscode (?status?‘Junior’(Professor) Taught) SQL Solution SELECT crscode FROM Course C WHERE c.crscode NOT IN( (SELECT crscode FROM Taught T, Professor P WHERE T.ssn = P.ssn AND P.status=‘Junior’ ) * * * * * * * * * * * * * * * * * * SQL Solution SELECT T1.crscode FROM Taught T1, Taught T2 WHERE T1.crscode=T2.crscode AND T1.semest