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Autores Quentin Cappart
Prazo de entrega Sem prazo
Limite de submissão No limitation

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Algèbre relationnelle (encore ?!!)

Bien que leur sémantique ne soit pas exactement pareille, il existe un lien fort entre algèbre relationnelle et requêtes SQL. Pour ces questions, écrivez une requête SQL retournant le même résultat que ces requêtes formalisées en algèbre relationnelle.

Attention: rappelez vous bien que l'algèbre relationnelle supprime automatiquement les duplicatas.

Questão 1:

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

Questão 2:

\(\sigma_{dept\_name = 'Biology'}(student)\)

Questão 3:

\(\pi_{name, tot\_cred}(student)\)

Questão 4:

\(\pi_{name}(\sigma_{tot\_cred > 60}(student))\)

Questão 5:

\(\sigma_{salary < 80000}(instructor)\)

Questão 6:

\(\pi_{course\_id}(\sigma_{credits = 3}(course))\)

Questão 7:

\(\pi_{name}(\sigma_{dept\_name = 'Physics'}(student))\)

Questão 8:

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

Questão 9:

\(\pi_{course.title}\big(\sigma_{course.course\_id = section.course\_id \land section.year = 2008}(course \times section)\big)\)

Questão 10:

\(\pi_{student.name}\big(\sigma_{student.ID = takes.ID \land takes.course\_id = '802'}(student \times takes)\big)\)