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Forfatter(e) Quentin Cappart
Frist Ingen frist
Innleveringsgrense Ingen begrensning

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Lecture d'algèbre relationnelle

Pour cette question, on va considérer ces relations de la base de données university :

  • \(\mathsf{course}(\underline{course\_id}, title, dept\_name, credits)\)
  • \(\mathsf{prereq}(\underline{course\_id},\underline{prereq\_id})\)
  • \(\mathsf{department}(\underline{dept\_name}, building, budget)\)
  • \(\mathsf{student}(\underline{ID}, name, dept\_name, tot\_credit)\)
  • \(\mathsf{instructor}(\underline{ID}, name, dept\_name, salary)\)
  • \(\mathsf{advisor}(\underline{s\_ID}, i\_ID)\)

Nous n'avons pas besoin de connaître les tuples de la table. Réferez vous au diagramme des schémas pour repérer les référencements via les clefs étrangères.

Indiquez l'énoncé correspondant aux requêtes suivantes.

Spørsmål 1:

\(\pi_{ID}(student) - \pi_{s\_ID}(advisor)\)

Spørsmål 2:

\(\pi_{dept\_name}(student) - \pi_{dept\_name}(department)\)

Spørsmål 3:

\(|\pi_{dept\_name}(student \bowtie_{student.dept\_name=department.dept\_name} department)|\)

Spørsmål 4:

\(\pi_{ID}(student \bowtie advisor)\)

Spørsmål 5:

\(\pi_{course\_id}(course) - \pi_{course\_id}(prereq)\)

Spørsmål 6:

\(\pi_{student.name}(\sigma_{student.ID=advisor.s\_ID \land advisor.i\_ID=instructor.ID}(student \times advisor \times instructor))\)

Spørsmål 7:

\(\pi_{dept\_name}(department) - \pi_{dept\_name}(course)\)

Spørsmål 8:

\(\pi_{ID,name}(student) - \pi_{student.ID,student.name}(student \bowtie advisor)\)

Spørsmål 9:

\(|\pi_{i\_ID}(advisor)|\)

Spørsmål 10:

\(\pi_{dept\_name}(student) \cap \pi_{dept\_name}(instructor)\)

Spørsmål 11:

\(\pi_{student.ID}(\sigma_{student.dept\_name=instructor.dept\_name \land instructor.salary>90000}(student \times instructor))\)

Spørsmål 12:

\(\pi_{ID}(student) - \pi_{student.ID}(\sigma_{student.dept\_name=instructor.dept\_name}(student \times instructor))\)

Spørsmål 13:

\(\pi_{ID}(student) - \pi_{ID}(student \bowtie_{student.dept\_name=instructor.dept\_name} instructor)\)

Spørsmål 14:

\(\pi_{dept\_name}(student) \subseteq \pi_{dept\_name}(department)\)

Spørsmål 15:

\(\pi_{i\_ID}(advisor) - \pi_{ID}(instructor)\)

Spørsmål 16:

\(|\pi_{dept\_name}(student \times instructor)|\)

Spørsmål 17:

\(\pi_{dept\_name}(course) - \pi_{dept\_name}(student)\)

Spørsmål 18:

\(\pi_{student.ID}(student) \cap \pi_{advisor.s\_ID}(advisor)\)

Spørsmål 19:

\(\pi_{course\_id}(\sigma_{course.dept\_name=department.dept\_name}(course \times department))\)

Spørsmål 20:

\(\pi_{dept\_name}(student \bowtie_{student.dept\_name=department.dept\_name} department) = \pi_{dept\_name}(student)\)