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2. Relational database - Wikipedia

   en.wikipedia.org/wiki/Relational_database

   A relational database has become the predominant type of database. Other models besides the relational model include the hierarchical database model and the network model. The table below summarizes some of the most important relational database terms and the corresponding SQL term:

3. Relational model - Wikipedia

   en.wikipedia.org/wiki/Relational_model

   The flexibility of relational databases allows programmers to write queries that were not anticipated by the database designers. As a result, relational databases can be used by multiple applications in ways the original designers did not foresee, which is especially important for databases that might be used for a long time (perhaps several ...

4. Relation (database) - Wikipedia

   en.wikipedia.org/wiki/Relation_(database)

   In database theory, a relation, as originally defined by E. F. Codd, [1] 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. Codd's original definition notwithstanding, and contrary to the usual definition in mathematics, there is no ordering to the elements of the tuples of a relation.

5. Database normalization - Wikipedia

   en.wikipedia.org/wiki/Database_normalization

   Database normalization is the process of structuring a relational database accordance with a series of so-called normal forms in order to reduce data redundancy and improve data integrity. It was first proposed by British computer scientist Edgar F. Codd as part of his relational model .

6. Codd's 12 rules - Wikipedia

   en.wikipedia.org/wiki/Codd's_12_rules

   Codd's twelve rules [1] are a set of thirteen rules (numbered zero to twelve) proposed by Edgar F. Codd, a pioneer of the relational model for databases, designed to define what is required from a database management system in order for it to be considered relational, i.e., a relational database management system (RDBMS).

7. Database model - Wikipedia

   en.wikipedia.org/wiki/Database_model

   The basic data structure of the relational model is the table, where information about a particular entity (say, an employee) is represented in rows (also called tuples) and columns. Thus, the "relation" in "relational database" refers to the various tables in the database; a relation is a set of tuples. The columns enumerate the various ...

8. SQL - Wikipedia

   en.wikipedia.org/wiki/SQL

   SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd [12] in the early 1970s. [13] This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...

9. Entity–relationship model - Wikipedia

   en.wikipedia.org/wiki/Entity–relationship_model

   Consequently, the ER model becomes an abstract data model, [1] that defines a data or information structure that can be implemented in a database, typically a relational database. Entity–relationship modeling was developed for database and design by Peter Chen and published in a 1976 paper, [2] with variants of the idea existing previously. [3]