Skip to main content
Computer Science

Return to Question

typos, language, format, tags. "algebra" didn't belong & the calculus is "tuple"
Source Link
edit approved Sep 9, 2021 at 1:36
philipxy
edit approved Sep 9, 2021 at 1:36
philipxy
  • 154
  • 1
  • 9

Relational Algebra Tuple relational calculus: existential quantifiers

So iI have the following question and templategiven answer:

Question: List the names of managers who have at least one dependant.

Answer: {e.Fname, e.Lname | EMPLOYEE(e) AND (∃d)(∃t)(DEPARTMENT(d) AND DEPENDANT(t) AND e.Ssn = d.Mgrssn AND t.Essn = e.Ssn) }

Question: List the names of managers who have at least one dependant.

Answer: {e.Fname, e.Lname | EMPLOYEE(e) AND (∃d)(∃t)(DEPARTMENT(d) AND DEPENDANT(t) AND e.Ssn = d.Mgrssn AND t.Essn = e.Ssn) }

My answer was exactly the same except that instead of the (∃d)(∃t)(...)(∃d)(∃t)(...) section I said (∃d)(DEPARTMENT(d) AND e.Ssn = d.Mgrssn) AND (∃t)(DEPENDANT(t) AND t.Essn = e.Ssn)(∃d)(DEPARTMENT(d) AND e.Ssn = d.Mgrssn) AND (∃t)(DEPENDANT(t) AND t.Essn = e.Ssn).

My question is basically areAre these equivalent?

Relational Algebra: existential quantifiers

So i have the following question and template answer:

Question: List the names of managers who have at least one dependant.

Answer: {e.Fname, e.Lname | EMPLOYEE(e) AND (∃d)(∃t)(DEPARTMENT(d) AND DEPENDANT(t) AND e.Ssn = d.Mgrssn AND t.Essn = e.Ssn) }

My answer was exactly the same except that instead of the (∃d)(∃t)(...) section I said (∃d)(DEPARTMENT(d) AND e.Ssn = d.Mgrssn) AND (∃t)(DEPENDANT(t) AND t.Essn = e.Ssn).

My question is basically are these equivalent?

Tuple relational calculus: existential quantifiers

I have the following question and given answer:

Question: List the names of managers who have at least one dependant.

Answer: {e.Fname, e.Lname | EMPLOYEE(e) AND (∃d)(∃t)(DEPARTMENT(d) AND DEPENDANT(t) AND e.Ssn = d.Mgrssn AND t.Essn = e.Ssn) }

My answer was exactly the same except that instead of the (∃d)(∃t)(...) section I said (∃d)(DEPARTMENT(d) AND e.Ssn = d.Mgrssn) AND (∃t)(DEPENDANT(t) AND t.Essn = e.Ssn).

Are these equivalent?

added 112 characters in body
Source Link
pk00
pk00
  • 27
  • 7

So i have the following question and template answer: enter image description here

Question: List the names of managers who have at least one dependant.

Answer: {e.Fname, e.Lname | EMPLOYEE(e) AND (∃d)(∃t)(DEPARTMENT(d) AND DEPENDANT(t) AND e.Ssn = d.Mgrssn AND t.Essn = e.Ssn) }

My answer was exactly the same except that instead of the (∃d)(∃t)(...) section I said (∃d)(DEPARTMENT(d) AND e.Ssn = d.Mgrssn) AND (∃t)(DEPENDANT(t) AND t.Essn = e.Ssn).

My question is basically are these equivalent?

So i have the following question and template answer: enter image description here

My answer was exactly the same except that instead of the (∃d)(∃t)(...) section I said (∃d)(DEPARTMENT(d) AND e.Ssn = d.Mgrssn) AND (∃t)(DEPENDANT(t) AND t.Essn = e.Ssn).

My question is basically are these equivalent?

So i have the following question and template answer:

Question: List the names of managers who have at least one dependant.

Answer: {e.Fname, e.Lname | EMPLOYEE(e) AND (∃d)(∃t)(DEPARTMENT(d) AND DEPENDANT(t) AND e.Ssn = d.Mgrssn AND t.Essn = e.Ssn) }

My answer was exactly the same except that instead of the (∃d)(∃t)(...) section I said (∃d)(DEPARTMENT(d) AND e.Ssn = d.Mgrssn) AND (∃t)(DEPENDANT(t) AND t.Essn = e.Ssn).

My question is basically are these equivalent?

Source Link
pk00
pk00
  • 27
  • 7

Relational Algebra: existential quantifiers

So i have the following question and template answer: enter image description here

My answer was exactly the same except that instead of the (∃d)(∃t)(...) section I said (∃d)(DEPARTMENT(d) AND e.Ssn = d.Mgrssn) AND (∃t)(DEPENDANT(t) AND t.Essn = e.Ssn).

My question is basically are these equivalent?