Given two relational schemas R(ABC) and S(ABC), let r(R) and s(S) be the relatio

Question

Given two relational schemas R(ABC) and S(ABC), let r(R) and s(S) be the relations (relation table or relation instance) corresponding to R and S respectively as the following:
R
A B C
a1 b1 c1
a3 b3 c3
S
A B C
a1 b1 c1
a2 b2 c2
1. Are table R and table S union compatible?
2. Please give the result of table R union table S.
3. Please give the result of table R intersect table S.
4. Please give the result of table R difference (minus) table S.
5. Please give the result of table S difference (minus) table R.
6. Is the operator difference (minus) commutative?
7. Is the operator difference (minus) associative?
(Please evaluate the results of the relational algebra expression manually without running SQL
statements.)

Explanation / Answer

1. for two relations to be union compatible they must have number of columns same , and domain of columns must be same.

So keeping in mind the only above two properties yes they are union compatible since number of columns is 3 in both the case and their domain are also same.

2. R union S is just the cross product of the two relations.

3.R intersect S is a1 b1 c1

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