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The trigger below is defined on the relation T (C, D) with the primary key on the attr

The trigger below is defined on the relation T (C, D) with the primary key on the attr

Computer Networking: A Top-Down Approach (7th Edition)
Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:James Kurose, Keith Ross
Chapter1: Computer Networks And The Internet
Section: Chapter Questions
Problem R1RQ: What is the difference between a host and an end system? List several different types of end...
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The trigger below is defined on the relation T(C, D) with the primary key on the attribute C. CREATE TRIGGER Secret AFTER DELETE ON T REFERENCING OLD ROW AS oldie FOR EACH ROW WHEN (oldie.C = ANY (SELECT D FROM T)) INSERT INTO T VALUES (oldie.C, oldie.D): Which of the following best explains the conditions as enforced by this trigger? a. Attribute D in T is a foreign key, referencing C. b. Every key value also appears in a non-key column. C. A key value that is present in a non-key column in another row cannot be removed. d. Attribute D is unique.
Transcribed Image Text:The trigger below is defined on the relation T(C, D) with the primary key on the attribute C. CREATE TRIGGER Secret AFTER DELETE ON T REFERENCING OLD ROW AS oldie FOR EACH ROW WHEN (oldie.C = ANY (SELECT D FROM T)) INSERT INTO T VALUES (oldie.C, oldie.D): Which of the following best explains the conditions as enforced by this trigger? a. Attribute D in T is a foreign key, referencing C. b. Every key value also appears in a non-key column. C. A key value that is present in a non-key column in another row cannot be removed. d. Attribute D is unique.
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