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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 (C) Signup and view all the answers

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

{ID} (D) Signup and view all the answers

What attribute should be chosen as a primary key?

An attribute that never or very rarely changes (A) 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 (C) 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 (A) 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 (B) Signup and view all the answers

What does a foreign key constraint enforce?

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