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Autores Quentin Cappart
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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.

Questão 1:

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

Questão 2:

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

Questão 3:

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

Questão 4:

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

Questão 5:

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

Questão 6:

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

Questão 7:

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

Questão 8:

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

Questão 9:

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

Questão 10:

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

Questão 11:

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

Questão 12:

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

Questão 13:

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

Questão 14:

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

Questão 15:

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

Questão 16:

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

Questão 17:

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

Questão 18:

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

Questão 19:

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

Questão 20:

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