23 Questions
Which of the following is a possible meaning of a null value in a relation?
The value is unknown
What can be interpreted as a fact in a relation?
Tuples in the relation
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
Why are composite attributes not allowed in relational databases?
Composite attributes are not atomic values
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
What is the purpose of a foreign key?
To establish a relationship between two relations
Constraints are the ________ or the limitations on data in the database.
restrictions
The first constraint under schema based constraint is the ________ constraints.
domain
A ________ is a set of attributes that can help in identifying each tuple in relation uniquely.
super key
Foreign key must be of the same ______ as the attribute it refers to
domain
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.
What is the entity integrity constraint?
The entity integrity constraint states that no primary key value can be null.
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.
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.
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.
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.
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.
What is the purpose of a foreign key?
To refer to the primary key of another relation.
What is a key constraint?
A set of attributes that can help in identifying each tuple in a relation uniquely.
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
What is the purpose of domain constraints in the relational model?
To restrict the data type of attribute values within each tuple
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
What is the purpose of the entity integrity constraint?
To ensure that no primary key value can be null
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
