Database-Management-System

Question 444

Following table has two attributes Employee_id and Manager_id, where Employee_id is a primary key and manager_id is a foreign key referencing Employee_id with on-delete cascade:

On deleting the table (20,40), the set of other tuples that must be deleted to maintain the referential integrity of table is

A	(30,35) only
B	(30,35) and (35,20) only
C	(35,20) only
D	(40,45) and (25,40) only

Database-Management-SystemConstraintsUGC NET June-2019 CS Paper-2

Question 444 Explanation:

If (20, 40) is deleted then the entry in manager_id containing 20 value will violate the referential integrity constraint so entry (35,20) is deleted because of deletion of (20,40).
Similarly entry (30,35) is deleted because of the deletion of entry (35,20).
After deletion of entry (30,35) referential integrity is maintained in given relation so no further deletion are made.
Hence correct option is option(2).

Correct Answer: B

Question 444 Explanation:

If (20, 40) is deleted then the entry in manager_id containing 20 value will violate the referential integrity constraint so entry (35,20) is deleted because of deletion of (20,40).
Similarly entry (30,35) is deleted because of the deletion of entry (35,20).
After deletion of entry (30,35) referential integrity is maintained in given relation so no further deletion are made.
Hence correct option is option(2).