The Gateway to Computer Science Excellence
0 votes
38 views
Let R = (A, B) and S = (A, C), and let r (R) and s(S) be relations.
Write relational-algebra expressions equivalent to the following domainrelational-
calculus expressions:
a. {< a > | ∃ b (< a, b > ∈ r ∧ b = 17)}
b. {< a, b, c > | < a, b > ∈ r ∧ < a, c > ∈ s}
c. {< a > | ∃ b (< a, b > ∈ r ) ∨ ∀c (∃ d (< d, c > ∈ s) ⇒< a, c > ∈ s)}
d. {< a > | ∃ c (< a, c > ∈ s ∧ ∃ b1, b2 (< a, b1 > ∈ r ∧ < c, b2 >
∈ r ∧ b1 > b2))}
in Databases by Boss (10.5k points) | 38 views

Please log in or register to answer this question.

Related questions

Quick search syntax
tags tag:apple
author user:martin
title title:apple
content content:apple
exclude -tag:apple
force match +apple
views views:100
score score:10
answers answers:2
is accepted isaccepted:true
is closed isclosed:true
50,666 questions
56,167 answers
193,833 comments
93,994 users