REG: Characteristic and Constraint of REL Model

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Which of the following is a possible meaning of a null value in a relation?

The value is unknown (correct)
The value is not applicable
The value does not exist
The value is not available

What can be interpreted as a fact in a relation?

The declaration or assertion
The relation schema
The attributes in the relation
Tuples in the relation (correct)

Which characteristic of a relation does not require any particular order to be maintained when displaying it as a table?

Ordering of tuples within a relation (correct)
Ordering of values within a tuple
Values and nulls in a tuple
None of the above

Why are composite attributes not allowed in relational databases?

Composite attributes are not atomic values (B) Signup and view all the answers

Which of the following is a condition that a foreign key must satisfy?

It must be of the same domain as the attribute it refers to (C) Signup and view all the answers

What is the purpose of a foreign key?

To establish a relationship between two relations (C) Signup and view all the answers

Constraints are the ________ or the limitations on data in the database.

restrictions Signup and view all the answers

The first constraint under schema based constraint is the ________ constraints.

domain Signup and view all the answers

A ________ is a set of attributes that can help in identifying each tuple in relation uniquely.

super key Signup and view all the answers

Foreign key must be of the same ______ as the attribute it refers to

domain Signup and view all the answers

What are the conditions that a foreign key must satisfy?

A foreign key must satisfy two conditions: 1) It has to be of the same domain as the attribute it refers to. 2) The value of the foreign key in a tuple either occurs as a value of the primary key or is null. Signup and view all the answers

What is the entity integrity constraint?

The entity integrity constraint states that no primary key value can be null. Signup and view all the answers

What is the referential integrity constraint?

The referential integrity constraint states that a tuple in one relation that refers to another relation must refer to an existing tuple in that relation. Signup and view all the answers

What are the three categories of constraints in the relational model?

The three categories of constraints in the relational model are inherent model-based constraints, schema-based constraints, and application-based constraints. Signup and view all the answers

What is a domain constraint?

A domain constraint specifies that within each tuple or row, the value of each attribute has to be atomic or indivisible. It also checks the data type of the values of each attribute. Signup and view all the answers

What is a key constraint?

A key constraint ensures that tuples in a relation are unique. It defines an attribute or set of attributes that can uniquely identify each tuple in a relation. Signup and view all the answers

Which of the following is a condition that a foreign key must satisfy?

The value of the foreign key in a tuple must occur as a value of the primary key. (C) Signup and view all the answers

What is the purpose of a foreign key?

To refer to the primary key of another relation. (B) Signup and view all the answers

What is a key constraint?

A set of attributes that can help in identifying each tuple in a relation uniquely. (A) Signup and view all the answers

Which category of constraints in the relational model cannot be directly defined in the schemas and are expressed and enforced by the application programs?

Application based constraints (B) Signup and view all the answers

What is the purpose of domain constraints in the relational model?

To restrict the data type of attribute values within each tuple (D) Signup and view all the answers

What is a key in the context of key constraints in the relational model?

An attribute that can uniquely identify each tuple in a relation (A) Signup and view all the answers

What is the purpose of the entity integrity constraint?

To ensure that no primary key value can be null (A) Signup and view all the answers

REG: Characteristic and Constraint of REL Model

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Questions and Answers

Which of the following is a possible meaning of a null value in a relation?

What can be interpreted as a fact in a relation?

Which characteristic of a relation does not require any particular order to be maintained when displaying it as a table?

Why are composite attributes not allowed in relational databases?

Which of the following is a condition that a foreign key must satisfy?

What is the purpose of a foreign key?

Constraints are the ________ or the limitations on data in the database.

The first constraint under schema based constraint is the ________ constraints.

A ________ is a set of attributes that can help in identifying each tuple in relation uniquely.

Foreign key must be of the same ______ as the attribute it refers to

What are the conditions that a foreign key must satisfy?

What is the entity integrity constraint?

What is the referential integrity constraint?

What are the three categories of constraints in the relational model?

What is a domain constraint?

What is a key constraint?

Which of the following is a condition that a foreign key must satisfy?

What is the purpose of a foreign key?

What is a key constraint?

Which category of constraints in the relational model cannot be directly defined in the schemas and are expressed and enforced by the application programs?

What is the purpose of domain constraints in the relational model?

What is a key in the context of key constraints in the relational model?

What is the purpose of the entity integrity constraint?

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