GATE | Quiz for Sudo GATE 2021 | Question 5
The following table has two attributes A and C where A is the primary key and C is the foreign key referencing A with on-delete cascade.
The set of all tuples that must be additionally deleted to preserve referential integrity when the tuple (4,6) is deleted is:
Note – This question is multiple select questions (MSQ).
(A) (11, 7)
(B) (7, 4)
(D) (9, 4)
Answer: (A) (B) (D)
Explanation: When (4,6) is deleted. Since C is a foreign key referring A with delete on cascade, all entries with value 4 in C must be deleted. So (7, 4) and (9, 4) are deleted. As a result of this 7 and 9 are deleted from A which causes (11, 7) to be deleted.
So, options (A), (B), and (D) are correct.
Quiz of this Question
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