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Lecture d'algèbre relationnelle

Considérez les 2 relations suivantes venant de la base de données university.

Table: instructor
ID name dept_name salary
10101 Srinivasan Comp. Sci. 65000
12121 Wu Finance 90000
15151 Mozart Music 40000
22222 Einstein Physics 95000
32343 El Said History 60000
33456 Gold Physics 87000
45565 Katz Comp. Sci. 75000
58583 Califieri History 62000
76543 Singh Finance 80000
76766 Crick Biology 72000
83821 Brandt Comp. Sci. 92000
98345 Kim Elec. Eng. 80000
Table: department
dept_name building budget
Biology Watson 90000
Comp. Sci. Taylor 100000
Elec. Eng. Taylor 85000
Finance Painter 120000
History Painter 50000
Music Packard 80000
Physics Watson 70000

Indiquez le résultat attendu de chaque expression d'algèbre relationnelle suivante.

Questão 1:

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

Questão 2:

\(\pi_{salary}(\sigma_{name='Gold'}(instructor))\)

Questão 3:

\(|\sigma_{salary>80000}(instructor)|\)

Questão 4:

\(\pi_{building}(\sigma_{dept\_name='Music'}(department))\)

Questão 5:

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

Questão 6:

\(\pi_{name}(\sigma_{budget=50000}(instructor \bowtie_{instructor.dept\_name=department.dept\_name} department))\)

Questão 7:

\(|\pi_{building}(department)|\)

Questão 8:

\(\pi_{dept\_name}(\sigma_{salary=72000}(instructor))\)

Questão 9:

\(|\pi_{salary}(instructor)|\)

Questão 10:

\(\pi_{name}(instructor) - \pi_{name}(\sigma_{salary>42000}(instructor))\)

Questão 11:

\(|\sigma_{budget<80000}(department)|\)

Questão 12:

\(\pi_{ID}(\sigma_{salary=72000}(instructor))\)

Questão 13:

\(|\sigma_{salary<budget}(instructor \bowtie_{instructor.dept\_name=department.dept\_name} department)|\)

Questão 14:

\(\pi_{dept\_name}(instructor) \cap \pi_{dept\_name}(\sigma_{building='Watson'}(department))\)

Questão 15:

\(|\sigma_{salary=40000}(instructor)|\)

Questão 16:

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

Questão 17:

\(|\pi_{dept\_name}(instructor) - \pi_{dept\_name}(department)|\)

Questão 18:

\(\pi_{name}(\sigma_{building='Packard'}(instructor \bowtie_{instructor.dept\_name=department.dept\_name} department))\)

Questão 19:

\(\pi_{building}(\sigma_{salary=95000}(instructor \bowtie_{instructor.dept\_name=department.dept\_name} department))\)

Questão 20:

\(|\pi_{name}(instructor) - \pi_{name}(\sigma_{dept\_name='Finance'}(instructor))|\)