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Relational Model

A database model introduced by E. F. Codd in 1970 based on predicate logic and set theory where data is organized into relations or tables.

Predicate Logic

A mathematical framework used to verify whether a statement of fact is true or false.

Set Theory

A branch of mathematics dealing with groups of objects called sets, used as the basis for data manipulation in the relational model.

Relation (Table)

A two-dimensional structure composed of rows and columns used to store data in a relational database.

Tuple

A row in a table that represents a single record or entity.

Attribute

A column in a table that represents a specific property or characteristic of an entity.

Attribute Domain

The set of valid values that an attribute can contain.

Key

An attribute or group of attributes that uniquely determines the values of other attributes.

Determination

A state where knowing the value of one attribute allows the value of another attribute to be determined.

Functional Dependence

A relationship where the value of one or more attributes determines the value of another attribute.

Determinant

The attribute whose value determines another attribute.

Dependent

The attribute whose value is determined by another attribute.

Composite Key

A key composed of more than one attribute used to uniquely identify a record.

Key Attribute

An attribute that is part of a key.

Superkey

An attribute or combination of attributes that uniquely identifies each row in a table.

Candidate Key

A minimal superkey that has no unnecessary attributes and can uniquely identify a row.

Primary Key

A candidate key selected to uniquely identify each row in a table and cannot contain null values.

Foreign Key

An attribute in one table that refers to the primary key in another table to create a relationship.

Secondary Key

An attribute or set of attributes used for data retrieval but not for unique identification.

Entity Integrity

A rule stating that primary key values must be unique and cannot contain null values.

Referential Integrity

A rule ensuring that foreign key values must match an existing primary key value or be null.

Relational Algebra

A set of mathematical operations used to manipulate data in relational tables.

Select Operator

An operation that retrieves specific rows from a table based on a condition.

Project Operator

An operation that retrieves specific columns from a table.

Union Operator

An operation that combines rows from two union-compatible tables and removes duplicates.

Intersect Operator

An operation that retrieves rows common to two union-compatible tables.

Difference Operator

An operation that retrieves rows found in one table but not in another.

Product Operator

An operation that creates all possible combinations of rows from two tables (Cartesian product).

Join Operator

An operation that combines rows from two tables based on a related column.

Divide Operator

An operation that retrieves values associated with all values in another table.

Entity Relationship Model (ERM)

Entity Relationship Diagram (ERD)

A diagram that depicts an entity relationship model’s entities, attributes, and relations.

Entity

Represented in the ERD by a rectangle (entity box) with the entity name written in the center.

Entity Instance / Entity Occurrence

Each row in the relational table in the ER model.

Entity Set

A collection of similar entities.

Relationship

Describes associations among data.

Connectivity

The type of relationship between entities represented in an ERD by a line.

Attribute

A characteristic that describes a particular property of an entity.

Chen Notation

A notation where relationships are represented by a diamond connected to entities with a relationship line.

Crow’s Foot Notation

A notation where entities are connected by lines and symbols show the cardinality of relationships.

Primary Key

The entity identifier mapped as the table’s primary key and usually underlined in Chen notation.

Foreign Key

An attribute used to mark relationships between tables in Crow’s Foot notation.

Unnormalized Data

Data Anomaly

An undesirable consequence of a data modification.

Normalization

A process that assigns attributes to entities to reduce or eliminate data redundancies.

Normal Form

Each rule in database normalization.

First Normal Form (1NF)

There are no repeating groups and the primary key is identified.

Second Normal Form (2NF)

Table is in 1NF and all columns depend on the table’s primary key.

Third Normal Form (3NF)

Table is in 2NF and no non-key attribute is determined by another non-key attribute.

Boyce-Codd Normal Form (BCNF)

Every determinant is a candidate key and it is a special case of 3NF.

Fourth Normal Form (4NF)

Table is in 3NF and has no independent multivalued dependencies.

Normalization Objective

Each table represents a single subject.

Normalization Objective

Each row and column intersection contains only one value.

Normalization Objective

No data item is unnecessarily stored in more than one table.

Normalization Objective

All nonprime attributes depend on the primary key.

Normalization Objective

Tables have no insertion, update, or deletion anomalies