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by earl, 5906 days ago
Relational Database Management System

Among hierarchical and networked databases, one of the basic database systems.

[create Edgar Codd] developed the relational model to eliminate the weak points of the until then used [create CODASYL]-system for network databases.

In 1970 Edgar F. Codd published "A Relational Model of Data for large Shared Data Banks" in Communications of the ACM.

In 1986 Edgar F. Codd described the basic rules which must apply to RDBMS. These rules consist of three "integrity rules", one "foundation rule" and 12 criterias.

The "foundation rule":

Any system which claims to be a relation database management system must be able to manage databases entirely through its relational capabilities.

An RDBMS must therefore support:
- A data definition language (DDL)
- A data manipulation language (DML)
- A data integrity language
- A data control language (DCL)
all of which must work on several records at a time, that is, on a relation.

Commonly the ACID criterias are applied to evaluate RDBMS: Atomicity, Consistency, Isolation, Durability - fulfilled ACID stability is required for transactional security (see also: [create Transaction Processing]).

Popular RDBMS include: Oracle, IBM's DB2, [create Informix], [create Sybase], [create Microsoft SQL Server]. [create PostgreSQL], FirebirdSQL and MySQL are an open source RDBMS. Another quite interesting is [create NCR Teradata] - one of the few "ultra high load" DBMS.
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