DATABASE SYSTEM CONCEPTS (LOOSELEAF)
DATABASE SYSTEM CONCEPTS (LOOSELEAF)
7th Edition
ISBN: 9781260515046
Author: SILBERSCHATZ
Publisher: MCG
Expert Solution & Answer
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Chapter 16, Problem 3PE

Explanation of Solution

a.

Proof:

Consider the expression given below:

ΠA(r − s) and ΠA(r)−ΠA(s)

Assume, r = {(1, 2)}, and s = {(1, 3)}...

Explanation of Solution

b.

Proof:

Consider the expression given below:

σB<4( Aγmax(B) as B(r)) and Aγmax(B) as BB<4(r))

Assume, r = {(1, 2), (1, 5)}...

Explanation of Solution

c.

Equivalence of expressions:

Yes”, the expressions will be equivalent if the max is replaced by min...

Explanation of Solution

d.

Proof:

Consider the expression given below:

(r⟖s)⟖t and r⟖(s⟖t)

Assume, r = {(1, 2)}, s = {(2, 3)}, t = {(1, 4)}...

Explanation of Solution

e.

Expression:

Proof:

Consider the expression given below:

σθ(E1⟕E2) and E1⟕σθ(E2)

Let R be of the schema (A, B) and S of (A, C).

Assume, r = {(1, 2)}, s = {(2, 3)} and let u be the expression C = 1...

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