Relational model

relationalrelational data modelrelationshipsrelational databaserelational datarelational database modelrelational model of data relationaldatabase keymodeling the relational patterns
The relational model (RM) for database management is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in 1969 by English computer scientist Edgar F. Codd, where all data is represented in terms of tuples, grouped into relations.wikipedia
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Relational database

relational database management systemRDBMSrelational databases
A database organized in terms of the relational model is a relational database.
A relational database is a digital database based on the relational model of data, as proposed by E. F. Codd in 1970.

Functional dependency

functional dependenciesfunctionally dependentinspired from relational database theory
The determination of functional dependencies is an important part of designing databases in the relational model, and in database normalization and denormalization.

Query optimization

query optimizeroptimizationQuery processing
In practice, relational database management systems rewrite ("optimize") queries to perform faster, using a variety of techniques.

Logical schema

logical data modelschemadatabase schema
Usually in the relational model a database schema is said to consist of a set of relation names, the headers that are associated with these names and the constraints that should hold for every instance of the database schema.
The relational model – where data is described in terms of tables and columns – had just been recognized as a data organization theory but no software existed to support that approach.

Domain relational calculus

domain calculus
In computer science, domain relational calculus (DRC) is a calculus that was introduced by Michel Lacroix and Alain Pirotte as a declarative database query language for the relational data model.

First normal form

1NF
A database that's in the first normal form is vulnerable to all types of anomalies, while a database that's in the domain/key normal form has no modification anomalies.

Data

statistical datascientific datadatum
The relational model (RM) for database management is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in 1969 by English computer scientist Edgar F. Codd, where all data is represented in terms of tuples, grouped into relations. The fundamental assumption of the relational model is that all data is represented as mathematical n-ary relations, an n-ary relation being a subset of the Cartesian product of n domains.

Relation (database)

relationrelation schemarelations
The relational model (RM) for database management is an approach to managing data using a structure and language consistent with first-order predicate logic, first described in 1969 by English computer scientist Edgar F. Codd, where all data is represented in terms of tuples, grouped into relations. The fundamental assumption of the relational model is that all data is represented as mathematical n-ary relations, an n-ary relation being a subset of the Cartesian product of n domains.

Declarative programming

declarativedeclarative languagedeclarative programming language
The purpose of the relational model is to provide a declarative method for specifying data and queries: users directly state what information the database contains and what information they want from it, and let the database management system software take care of describing data structures for storing the data and retrieval procedures for answering queries.

Database schema

schemarelational schemaschemas
A table in an SQL database schema corresponds to a predicate variable; the contents of a table to a relation; key constraints, other constraints, and SQL queries correspond to predicates.

System

systemssubsystemsubsystems
Some systems using these older architectures are still in use today in data centers with high data volume needs, or where existing systems are so complex and abstract that it would be cost-prohibitive to migrate to systems employing the relational model.

Data center

data centersdata centredatacenter
Some systems using these older architectures are still in use today in data centers with high data volume needs, or where existing systems are so complex and abstract that it would be cost-prohibitive to migrate to systems employing the relational model.

Object-oriented programming

object-orientedobject orientedobject-oriented programming language
In The Third Manifesto (first published in 1995) Date and Darwen attempt to show how the relational model can allegedly accommodate certain "desired" object-oriented features.

Three-valued logic

ternary logicthree-valuedlaw of excluded fourth
Codd himself, some years after publication of his 1970 model, proposed a three-valued logic (True, False, Missing/NULL) version of it to deal with missing information, and in his The Relational Model for Database Management Version 2 (1990) he went a step further with a four-valued logic (True, False, Missing but Applicable, Missing but Inapplicable) version.

Arity

nullaryn-arymonadic
The fundamental assumption of the relational model is that all data is represented as mathematical n-ary relations, an n-ary relation being a subset of the Cartesian product of n domains.

Cartesian product

productCartesian squareCartesian power
The fundamental assumption of the relational model is that all data is represented as mathematical n-ary relations, an n-ary relation being a subset of the Cartesian product of n domains.

Reason

reasoningratiocinationhuman reason
In the mathematical model, reasoning about such data is done in two-valued predicate logic, meaning there are two possible evaluations for each proposition: either true or false (and in particular no third value such as unknown, or not applicable, either of which are often associated with the concept of NULL).

Evaluation

evaluateevaluativeevaluating
In the mathematical model, reasoning about such data is done in two-valued predicate logic, meaning there are two possible evaluations for each proposition: either true or false (and in particular no third value such as unknown, or not applicable, either of which are often associated with the concept of NULL).

Proposition

propositionspropositionalclaim
In the mathematical model, reasoning about such data is done in two-valued predicate logic, meaning there are two possible evaluations for each proposition: either true or false (and in particular no third value such as unknown, or not applicable, either of which are often associated with the concept of NULL).

Expressive power (computer science)

expressive powerexpressiveexpressiveness
Data are operated upon by means of a relational calculus or relational algebra, these being equivalent in expressive power.

Information

informativeinputinputs
The relational model of data permits the database designer to create a consistent, logical representation of information.

Logical equivalence

logically equivalentequivalentequivalence
The theory includes a process of database normalization whereby a design with certain desirable properties can be selected from a set of logically equivalent alternatives.

Performance tuning

tuningperformanceHigh-performance tuning
This contrasts with common practice for SQL DBMSs in which performance tuning often requires changes to the logical model.

Data domain

domaindomain constraintsdomains
The basic relational building block is the domain or data type, usually abbreviated nowadays to type.

Data type

typedatatypetypes
The basic relational building block is the domain or data type, usually abbreviated nowadays to type.