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2. Relational database - Wikipedia

   en.wikipedia.org/wiki/Relational_database

   A relational database (RDB [1]) is a database based on the relational model of data, as proposed by E. F. Codd in 1970. [ 2 ] A database management system used to maintain relational databases is a relational database management system ( RDBMS ).

3. 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 ...

4. 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).

5. Relational model - Wikipedia

   en.wikipedia.org/wiki/Relational_model

   The relational model (RM) 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, [1] [2] where all data are represented in terms of tuples, grouped into relations.

6. 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.

7. Outline of databases - Wikipedia

   en.wikipedia.org/wiki/Outline_of_databases

   Relational model – for database management is a database model based on first-order predicate logic, first formulated and proposed in 1969 by Edgar F. Object–relational database (ORD) – database management system (DBMS) similar to a relational database, but with an object-oriented database model: objects, classes and inheritance are ...

8. Codd's theorem - Wikipedia

   en.wikipedia.org/wiki/Codd's_theorem

   Codd's theorem states that relational algebra and the domain-independent relational calculus queries, two well-known foundational query languages for the relational model, are precisely equivalent in expressive power. That is, a database query can be formulated in one language if and only if it can be expressed in the other.

9. Database schema - Wikipedia

   en.wikipedia.org/wiki/Database_schema

   The database schema is the structure of a database described in a formal language supported typically by a relational database management system (RDBMS). The term " schema " refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of relational databases ).