What is a foreign key?(a) A foreign key is a primary key of a relation which is an attribute in another relation(b) A foreign key is a superkey of a relation which is an attribute in more than one other relations(c) A foreign key is an attribute of a relation that is a primary key of another relation(d) A foreign key is the primary key of a relation that does not occur anywhere else in the schemaThis question was posed to me in a job interview.Origin of the question is Introduction to the Relational Model in portion Introduction to Relational Model and Sql of RDBMS

What is a foreign key?(a) A foreign key is a primary key of a relation

1.	What is a foreign key?(a) A foreign key is a primary key of a relation which is an attribute in another relation(b) A foreign key is a superkey of a relation which is an attribute in more than one other relations(c) A foreign key is an attribute of a relation that is a primary key of another relation(d) A foreign key is the primary key of a relation that does not occur anywhere else in the schemaThis question was posed to me in a job interview.Origin of the question is Introduction to the Relational Model in portion Introduction to Relational Model and Sql of RDBMS
Answer» Correct ANSWER is (c) A FOREIGN key is an attribute of a relation that is a primary key of ANOTHER relation The explanation is: A foreign key is an attribute of a relation that is INITIALLY a primary key of another relation. A foreign key USAGE preserves referential integrity.

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