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Relational Databases Keys Quiz

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Questions and Answers

What is the primary purpose of keys in relational databases?

To uniquely distinguish tuples within a relation based on their attributes (correct)

To aggregate data within a relation

To sort tuples within a relation

To perform mathematical operations on attribute values

Why is 'name' not considered a super key in the given context?

Because 'name' is a primary key

Because 'name' is not unique across tuples (correct)

Because 'name' is a foreign key

Because 'name' is an extraneous attribute

What defines a candidate key in a relational database?

A candidate key is any attribute in a relation

A candidate key is a super key that contains extraneous attributes

A candidate key is the primary key of a relation

A candidate key is a minimal super key (correct)

Why does the combination of {ID, name} not form a candidate key for the 'instructor' relation?

Because the combination does not uniquely identify tuples Signup and view all the answers

Which attribute combination is considered a super key for the 'instructor' relation?

{ID} Signup and view all the answers

What attribute should be chosen as a primary key?

An attribute that never or very rarely changes Signup and view all the answers

In which scenario should a composite key be chosen over a single simple key for a primary key?

When there is a need for uniqueness Signup and view all the answers

What is the relationship between a foreign key and a primary key?

A foreign key is generally a primary key from one table appearing as a field in another Signup and view all the answers

What does a referential integrity constraint require?

Values in referencing relation to appear in specified attributes of at least one tuple in the referenced relation Signup and view all the answers

What does a foreign key constraint enforce?

Value in one relation to appear in another Signup and view all the answers