Question

Consider the four relations R1(A, B, C), R2(X, Y, Z), R3(A, B, D)
and R4(U, X, Y). The domains of the attributes are: A-integers; B-
strings; C-single characters; D-'M', 'F'}; U-integers; X-strings;
Y-single characters; Z-{'M', 'F'}
Identify the pair of union-compatible relations
(A) Pair R1, R3
(B) Pair R1.R4
N
(C) Pair R2, R3
(D) Pair R3, R4​

Answer 1

Answer:

option a is the right answer

Explanation:

pair R1,R3

Answer 2

pairs (R1,R3) (R1,R4) (R3,R4) are union compatible relations.

Explanation:

1. given two sets R and S are said to be union compatible, only if they satisfy these two conditions:                                                                                                                                                                  (i) both relations R and S should have same number of attributes. For example, S(name, date) and R(name) then S and R are not union - compatible.                                                                                                                                   (ii)domain of each attribute of one relation and domain of its corresponding attribute from other relation should be same. For example, S(name, age) and R(name, hobby) are not union compatible as 2nd attributes of both relation have different domains  
2. here we have, R1(A,B,C) R2(X,Y,Z) R3(A,B,D) R4(U,X,Y)  
3. (R2,R3)- is not union compatible as attributes have different domain    
4. (R1,R2), (R1,R4) and (R3,R4)- are union compatible satisfying both the conditions