Relational Model

In the relational data model, a relation is defined as:

• A table with rows and columns

• A collection of attributes only

• A set of schemas

• A physical data storage format

Which of the following describes an attribute in a relational model?

• A row in a table

• A column in a table

• A key constraint

• A unique identifier for data

A tuple in the context of a relational database refers to:

• A set of tables

• A single row in a table

• The degree of a relation

• The name of a relation

Which of the following is true about a domain?

• It defines a permissible set of values for an attribute

• It specifies the structure of the database

• It ensures referential integrity

• It contains multiple relations

The term "instance" in the relational model refers to:

• A permanent structure of a relation

• A specific collection of data in a relation at a given time

• The process of defining a relation

• A constraint applied to a relation

Cardinality in a relational model is:

• The number of attributes in a relation

• The number of tuples in a relation

• The number of foreign keys in a table

• The degree of a relation

Degree in a relational model refers to:

• The number of tuples in a relation

• The number of attributes in a relation

• The number of candidate keys in a relation

• The number of primary keys in a table

A schema defines:

• The structure of a relation

• The specific data in a relation

• The constraints of an attribute

• The storage location of the database

Constraints in a relational model are used to:

• Define relationships between databases

• Ensure the validity of data in a relation

• Create alternate schemas

• Modify the structure of data instances

A candidate key is:

• A key selected as the primary key

• A unique key that can uniquely identify each row in a table

• A composite key containing multiple attributes

• Always the same as the primary key