Traduction en algèbre relationnelle

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Tác giả	Quentin Cappart
Hạn chót	Không có hạn chót
Giới hạn nộp bài	Không có giới hạn

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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.

Répondez aux questions suivantes.

Dán dòng lệnh này vào terminal của bạn:

Mật khẩu để kết nối là

Câu hỏi 1:

Donner les noms des étudiants inscrits dans le département au nom Comp. Sci.

\(\sigma_{dept\_name='Comp. Sci'}(student)\)

\(\pi_{student.name}(student \bowtie_{student.dept\_name=department.dept\_name} \sigma_{dept\_name='Comp. Sci'}(department))\)

\(\pi_{name}(\sigma_{dept\_name='Comp. Sci'}(department))\)

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

\(\pi_{name}(\sigma_{dept\_name='Comp. Sci'}(student))\)

Câu hỏi 2:

Donner les identifiants des étudiants qui ont un superviseur (advisor).

\(\pi_{s\_ID}(advisor)\)

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

\(\pi_{ID}(instructor)\)

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

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

Câu hỏi 3:

Donner les noms des instructeurs supervisant au moins un étudiant.

\(\pi_{instructor.name}(instructor \bowtie_{instructor.ID=advisor.i\_ID} advisor)\)

\(\pi_{name}(advisor)\)

\(\pi_{name}(student)\)

\(\pi_{name}(instructor \bowtie_{instructor.ID=advisor.i\_ID} advisor)\)

\(\pi_{name}(instructor)\)

Câu hỏi 4:

Donner les titres des cours offerts par le département au nom Physics.

\(\sigma_{dept\_name='Physics'}(department)\)

\(\pi_{title}(\sigma_{dept\_name='Physics'}(course))\)

\(\pi_{title}(prereq)\)

\(\pi_{title}(department)\)

\(\pi_{course.title}(course \bowtie_{course.dept\_name=department.dept\_name} \sigma_{dept\_name='Physics'}(department))\)

Câu hỏi 5:

Donner les identifiants des cours ayant au moins un prérequis.

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

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

\(\pi_{course.course\_id}(course \bowtie_{course.course\_id=prereq.course\_id} prereq)\)

\(\sigma_{course\_id}(prereq)\)

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

Câu hỏi 6:

Donner les identifiants des cours qui sont prérequis d'au moins un autre cours.

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

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

\(\pi_{course.course\_id}(course \bowtie_{course.course\_id=prereq.prereq\_id} prereq)\)

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

\(\sigma_{prereq\_id}(course)\)

Câu hỏi 7:

Donner les noms des étudiants conseillés par un instructeur du département Physics.

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

\(\pi_{student.name}(student \bowtie advisor)\)

\(\pi_{name}(instructor)\)

\(\pi_{student.name}(\sigma_{dept\_name='Physics'}(instructor) \bowtie_{instructor.ID=advisor.i\_ID} advisor \bowtie_{advisor.s\_ID=student.ID} student)\)

\(\pi_{name}(student)\)

Câu hỏi 8:

Donner les noms des étudiants ayant le même département que leur superviseur.

\(\pi_{name}(student)\)

\(\pi_{instructor.name}(advisor)\)

\(\pi_{student.name}(\sigma_{student.dept\_name=instructor.dept\_name}(student \bowtie_{student.ID=advisor.s\_ID} advisor \bowtie_{advisor.i\_ID=instructor.ID} instructor))\)

\(\pi_{student.name}(student \bowtie instructor)\)

\(\sigma_{dept\_name}(advisor)\)

Câu hỏi 9:

Donner les noms des départements n'ayant aucun étudiant.

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

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

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

\(\sigma_{dept\_name}(student)\)

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

Câu hỏi 10:

Donner les identifiants des étudiants qui n'ont pas de superviseur.

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

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

\(\sigma_{ID}(advisor)\)

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

\(\pi_{s\_ID}(advisor)\)

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