Question

Suppose two relations R(A:int, B:int) and S(A:int, B:string). Which of the following statements is valid?

Select one:
a. R\S
b. ∪
c. '∩'
d. R x S

Answer 1

The valid operation between two relations R(A:int, B:int) and S(A:int, B:string) is d. R x S, which is the Cartesian product. It is the only operation that does not require the schemas of the relations to be the same.

Step-by-step explanation:

The question is asking which operation is valid between two relations R and S with different attribute types for column B. Let's examine the options provided in the context of relational algebra:

• a. R\S: This operation is not well-defined between R and S since they have different schemas. Set difference requires the relations to have identical schemas.
• b. ∪: This symbol typically denotes union, which also requires the relations to have identical schemas, which is not the case here.
• c. '∩': This represents intersection, and like set difference and union, it requires both relations to have identical schemas.
• d. R x S: This represents the Cartesian product. The Cartesian product does not require the schemas of R and S to be the same and will create a new relation by combining every tuple in R with every tuple in S.

Therefore, the valid operation between R(A:int, B:int) and S(A:int, B:string) is d. R x S, the Cartesian product.