Relational Database Model: Keys, Dependencies, and Table Characteristics

What is a superkey?

A key that can uniquely identify any row in the table

What is a composite key?

A key that is composed of more than one attribute

What is a foreign key?

A primary key from another table used to implement relationships between tables

What is the order of rows and columns in a relational table?

Irrelevant to the DBMS

What does it mean for a key attribute to be part of a key?

It is an attribute that contributes to the uniqueness of a key

What is the significance of null in a database?

It represents the absence of any data value

What is the significance of the primary key in a table?

It uniquely identifies each row in the table

What does the relational database model enable?

Logical representation of data and its relationships

What is the attribute domain?

The specific range of values that a column can have

What is functional dependence?

The value of one or more attributes determines the value of one or more other attributes

What is full functional dependence?

When the entire collection of attributes in the determinant is necessary for the relationship

What is referential integrity?

A rule that ensures all values in the foreign key must either be valid values for a primary key or can be NULL

What is entity integrity?

A rule that ensures all values in the primary key must be unique and cannot contain nulls

What does each row in a relational table represent?

A single entity occurrence within the entity set

What is a relation in the context of a relational database?

A table that is a two-dimensional structure composed of columns and rows

What does each column in a relational table represent?

An attribute with a distinct name

Who is the creator of the relational database model?

E. F. Codd

What does it mean if an attribute A determines attribute B?

Every time you see a value of A, you will see the same value of B associated with it

What is a dependent attribute?

An attribute whose value is determined by another attribute

What is a key attribute?

An attribute that is part of a key

What is a known, but missing, attribute value?

An attribute value that is known to be absent

What is an unknown attribute value?

An attribute value that is not known

What is a determinant in a functional dependency?

An attribute whose value determines another attribute

What is the relationship between superkeys and composite keys?

Any composite key that includes a superkey as a key attribute will also be a superkey