Relational database

relational databasesrelationaldatabase constraintsrelational querydatabaseconstraintdatabase constraintRDBMSCodd's relational modelcomputerized relational database
A relational database is a digital database based on the relational model of data, as proposed by E.wikipedia
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Database

database management systemdatabasesdatabase systems
A relational database is a digital database based on the relational model of data, as proposed by E. F. Codd in 1970.
Relational databases became dominant in the 1980s.

Relational model

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

Column (database)

columnscolumnAttribute
This model organizes data into one or more tables (or "relations") of columns and rows, with a unique key identifying each row.
In a relational database, a column is a set of data values of a particular simple type, one value for each row of the database.

Row (database)

rowsrowrecord
This model organizes data into one or more tables (or "relations") of columns and rows, with a unique key identifying each row.
In the context of a relational database, a row—also called a tuple—represents a single, implicitly structured data item in a table.

Foreign key

Foreignforeign key constraintforeign key references
Rows in a table can be linked to rows in other tables by adding a column for the unique key of the linked row (such columns are known as foreign keys).
In the context of relational databases, a foreign key is a field (or collection of fields) in one table that uniquely identifies a row of another table or the same table.

Table (database)

tabletablesdatabase table
This model organizes data into one or more tables (or "relations") of columns and rows, with a unique key identifying each row.
In relational databases, and flat file databases, a table is a set of data elements (values) using a model of vertical columns (identifiable by name) and horizontal rows, the cell being the unit where a row and column intersect.

SQL

Structured Query LanguageSQL DatabasesWikibook SQL
Virtually all relational database systems use SQL (Structured Query Language) for querying and maintaining the database.
SQL is designed for a specific purpose: to query data contained in a relational database.

Tuple

5-tuplen''-tupletuples
Rows are also called records or tuples. A relation is defined as a set of tuples that have the same attributes.
Relational databases may formally identify their rows (records) as tuples.

Edgar F. Codd

E. F. CoddCoddE.F. Codd
A relational database is a digital database based on the relational model of data, as proposed by E. F. Codd in 1970.
Edgar Frank "Ted" Codd (19 August 1923 – 18 April 2003) was an English computer scientist who, while working for IBM, invented the relational model for database management, the theoretical basis for relational databases and relational database management systems.

Relation (database)

relationrelation schemarelations
A relation is defined as a set of tuples that have the same attributes.
In relational database theory, a relation, as originally defined by E. F. Codd, is a set of tuples (d 1, d 2, ..., d n ), where each element d j is a member of D j, a data domain.

Query language

querydatabase languagedatabase query language
.QL is a proprietary object-oriented query language for querying relational databases; successor of Datalog;

View (SQL)

viewviewsdatabase view
In implementations these are called "views" or "queries".
Unlike ordinary base tables in a relational database, a view does not form part of the physical schema: as a result set, it is a virtual table computed or collated dynamically from data in the database when access to that view is requested.

One-to-many (data model)

one-to-manymany-to-oneone-to-many relationships
When each cell can contain only one value and the PK migrates into a regular entity table, this design pattern can represent either a one-to-one or one-to-many relationship.
In a relational database, a one-to-many relationship exists when one row in table A may be linked with many rows in table B, but one row in table B is linked to only one row in table A. It is important to note that a one-to-many relationship is not a property of the data, but rather of the relationship itself.

One-to-one (data model)

one-to-one
When each cell can contain only one value and the PK migrates into a regular entity table, this design pattern can represent either a one-to-one or one-to-many relationship.
In a relational database, a one-to-one relationship exists when one row in a table may be linked with only one row in another table and vice versa.

Relvar

Base relvarrelation variablerelvars
Queries made against the relational database, and the derived relvars in the database are expressed in a relational calculus or a relational algebra.
In relational databases, relvar is a term introduced by C. J. Date and Hugh Darwen as an abbreviation for relation variable in their 1995 paper The Third Manifesto, to avoid the confusion sometimes arising from the use of the term relation, by the inventor of the relational model, E. F. Codd, for a variable to which a relation is assigned as well as for the relation itself.

Relational algebra

joinrelational logicθ''-join
Queries made against the relational database, and the derived relvars in the database are expressed in a relational calculus or a relational algebra.
The main application of relational algebra is providing a theoretical foundation for relational databases, particularly query languages for such databases, chief among which is SQL.

Compound key

composite keyCompound
Another common occurrence, especially in regard to N:M cardinality is the composite key.
Relational database

Database normalization

normalizationnormalizednormal form
The most common forms of normalization applied to databases are called the normal forms.
Database normalization is the process of structuring a relational database in accordance with a series of so-called normal forms in order to reduce data redundancy and improve data integrity.

Candidate key

candidatecandidate keyskey candidates
If the tuple contains a candidate or primary key then obviously it is unique; however, a primary key need not be defined for a row or record to be a tuple.
Relational database

Distributed Data Management Architecture

hierarchical directoriesrecord-oriented filestream-oriented file
The messages, protocols, and structural components of DRDA are defined by the Distributed Data Management Architecture.
In 1986, IBM marketed four different relational database (RDB) products, each built for a specific IBM operating system.

Relational database management system

RDBMSrelational database management systemsrelational database
A software system used to maintain relational databases is a relational database management system (RDBMS).

Natural key

Naturalnatural'' (or ''business'') key
Other, more natural keys may also be identified and defined as alternate keys (AK).

Primary key

alternate keydefining database keykey
Other, more natural keys may also be identified and defined as alternate keys (AK). Therefore, most physical implementations have a unique primary key (PK) for each row in a table.

Universally unique identifier

UUIDglobally unique identifierGUID
Additional technology may be applied to ensure a unique ID across the world, a globally unique identifier, when there are broader system requirements.