Question

1. Given two relations R1 and R2, where R1 contains N1 tuples and R2 contains N2 tuples, and N2>N1> 0, give the maximum and minimum possible sizes (in tuples) for the result relation produced by each of the following relational algebra expressions. In each case, state any assumptions about the schemas for R1 and R2 that are needed to make the expression meaningful.
(a) R1 U R2
(b) R1 ∩ R2
(c) R1 - R2
(d) R1 x R2

Answer 1

Answer:

Explanation:

A. Max is correct But min will be max(N1,N2) i.e. N2.

B. max=N1, min=0(no common tuples in R1 and R2)

C. max=N1(R1 and R2 are disjoint sets), min=0(all tuples of R1 are present in R2)

D. max=N1*N2, min=N1*N2