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Database Management Systems: Keys and Attributes

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Database Management Systems: Keys and Attributes

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Questions and Answers

What is an attribute that can be calculated from other attributes?

Derived attribute (correct)
Key attribute
Composite attribute
Multi-valued attribute

What is the minimal set of attributes that uniquely identifies an entity in the entity list?

Super key
Composite key
Key attribute (correct)
Primary key

What is a single candidate key designated as in a single entity?

Key attribute
Composite key
Primary key (correct)
Super key

What is an example of a derived attribute in an employee entity?

Employee age (A) Signup and view all the answers

What are the attributes that contain multiple values called?

Multi-valued attributes (B) Signup and view all the answers

What is a characteristic of a weak entity type?

It cannot exist without a related entity (B) Signup and view all the answers

What can be multiple in a single entity, according to the entity list?

Candidate keys (B) Signup and view all the answers

What are the attributes in the weak entity that participate in the primary key called?

Partial keys (D) Signup and view all the answers

What is the cardinality of the identifying relationship between the owner entity and the weak entity?

One-to-one or one-to-many (B) Signup and view all the answers

What is the relationship between the owner entity and the weak entity called?

Identifying relationship (C) Signup and view all the answers

What is a requirement for a weak entity in the identifying relationship?

It must have a total participation (B) Signup and view all the answers

What is a composite key composed of?

A group of attributes that make up the key (B) Signup and view all the answers

What is the primary key of a relation?

A minimal set of attributes that uniquely identify a relation (D) Signup and view all the answers

What is a super key?

Any set of attributes that uniquely identify a relation (B) Signup and view all the answers

What is the difference between a primary key and a super key?

A primary key is a minimal set of attributes, while a super key is any set of attributes (D) Signup and view all the answers

What is an example of a composite key?

(cust_id, product_code) (B) Signup and view all the answers

What is the purpose of a key in a relation?

To identify a specific row in a table (A) Signup and view all the answers