Database-Management-System

Question 19

Consider the following relations A, B, C.

How many tuples does the result of the following relational algebra expression contain? Assume that the schema of AUB is the same as that of A.

(AUB)⋈_{A.Id>40∨C.Id<15} C

Question 19 Explanation:

Performs the cross product and selects the tuples whose A∙Id is either greater than 40 or C∙Id is less than 15. It yields:

Correct Answer: A

Question 19 Explanation:

Performs the cross product and selects the tuples whose A∙Id is either greater than 40 or C∙Id is less than 15. It yields: