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+#REDIRECT [[Relational database]]
-{{mergeto|Relational database|discuss=Talk:Relational database#New merger proposal|date=April 2018}}
-[[File:RDBMS structure.png|thumbnail|right|The general structure of a relational database.]]
-A '''relational database management system''' ('''RDBMS''') is a [[database management system]] (DBMS) based on the [[relational model]] invented by [[Edgar F. Codd]] at IBM's [[IBM Almaden Research Center|San Jose Research Laboratory]]. Most databases in widespread use today are based on his [[relational database]] model.<ref>{{Cite book|url=https://www.amazon.com/Concepts-Database-Management-Philip-Pratt/dp/1285427106|title=Concepts of Database Management|last=Pratt|first=Philip J.|last2=Last|first2=Mary Z.|date=2014-09-08|publisher=Course Technology|isbn=9781285427102|edition=8|language=English|page=29}}</ref>
+{{R with history}}
-RDBMSs have been a common choice for the storage of information in databases used for financial records, manufacturing and logistical information, personnel data, and other applications since the 1980s. Relational databases have often replaced legacy [[hierarchical database]]s and [[network database]]s because they were easier to implement and administer. Nonetheless, relational databases received continued, unsuccessful challenges by [[object database]] management systems in the 1980s and 1990s, (which were introduced in an attempt to address the so-called [[object-relational impedance mismatch]] between relational databases and object-oriented application programs), as well as by [[XML database]] management systems in the 1990s.{{citation needed|date=March 2013}} However, due to the expanse of technologies, such as [[horizontal scaling]] of [[computer cluster]]s, [[NoSQL]] databases have recently become popular as an alternative to RDBMS databases.<ref>{{cite web|url=https://www.techrepublic.com/article/nosql-databases-eat-into-the-relational-database-market|access-date=2018-03-14|title=NoSQL databases eat into the relational database market}}</ref>
-==Market share==
-According to [[DB-Engines ranking|DB-Engines]], in June 2018, the most widely used systems were [[Oracle Corporation|Oracle]], [[MySQL]] ([[Free software]]), [[Microsoft SQL Server]], [[PostgreSQL]] ([[Free software]]), [[IBM DB2]], [[Microsoft Access]], and [[SQLite]] ([[Free software]]).<ref>{{cite web|url=http://db-engines.com/en/ranking/relational+dbms|accessdate=2017-05-31|title=DB-Engines Ranking of Relational DBMS}}</ref>
-According to research company [[Gartner]], in 2011, the five leading [[Proprietary software]] relational database vendors by revenue were [[Oracle Corporation|Oracle]] (48.8%), [[IBM]] (20.2%), [[Microsoft]] (17.0%), [[SAP AG|SAP]] including [[Sybase]] (4.6%), and [[Teradata]] (3.7%).<ref>{{cite web|url=http://itknowledgeexchange.techtarget.com/eye-on-oracle/oracle-the-clear-leader-in-24-billion-rdbms-market/|date=2012-04-12|accessdate=2013-03-01|title=Oracle the clear leader in $24 billion RDBMS market}}</ref>
-==History==
-In 1974, IBM began developing [[IBM System R|System R]], a research project to develop a prototype RDBMS.<ref>
-{{cite book
-|title=Funding a Revolution: Government Support for Computing Research
-|publisher=National Academies Press
-|isbn=0309062780
-|date=8 Jan 1999
-|url={{google books |plainurl=y |id=wvCbAgAAQBAJ}}
-}}</ref><ref>{{cite book
-|title=Fundamentals of Relational Database Management Systems
-|publisher=Springer
-|date=13 Feb 2008
-|isbn=3540483977
-|first1=S. |last1=Sumathi |first2=S. |last2=Esakkirajan
-|quote=The product was called SQL/DS (Structured Query Language/Data Store) and ran under the DOS/VSE operating system environment}}</ref>
-However, the first commercially available RDBMS  was [[Oracle Database|Oracle]], released in 1979 by Relational Software, now [[Oracle Corporation]].<ref>{{cite journal |date=May 2007 |title=Oracle Timeline |magazine=Profit Magazine |volume=12 |issue=2 |page=26 |publisher=Oracle |format=PDF |accessdate=2013-05-16 |url=http://www.oracle.com/us/corporate/profit/p27anniv-timeline-151918.pdf}}</ref>
-Other examples of an RDBMS include [[IBM DB2|DB2]], [[Adaptive Server Enterprise|SAP Sybase ASE]], and [[IBM Informix|Informix]]. In 1984, the first RDBMS for Macintosh began being developed, code-named Silver Surfer, it was later released in 1987 as [[4th Dimension (Software)|4th Dimension]] and known today as 4D.<ref>{{Cite web|url=http://articles.chicagotribune.com/1987-06-28/business/8702170525_1_silver-surfer-software-developers-macintosh-products|title=New Database Software Program Moves Macintosh Into The Big Leagues|website=tribunedigital-chicagotribune|access-date=2016-03-17}}</ref>
-==Historical usage of the term==
-The term "relational database" was invented by [[Edgar F. Codd|E. F. Codd]] at [[IBM]] in 1970. Codd introduced the term in his research paper "A Relational Model of Data for Large Shared Data Banks".<ref>[http://www.seas.upenn.edu/~zives/03f/cis550/codd.pdf "A Relational Model of Data for Large Shared Data Banks"]</ref>
-In this paper and later papers, he defined what he meant by "relational". One well-known definition of what constitutes a relational database system is composed of [[Codd's 12 rules]]. However, many of the early implementations of the relational model did not conform to all of Codd's rules, so the term gradually came to describe a broader class of database systems, which at a minimum:
-* Present the data to the user as [[relation (database)|relation]]s (a presentation in tabular form, i.e. as a ''collection'' of [[table (database)|table]]s with each table consisting of a set of rows and columns);
-* Provide relational operators to manipulate the data in tabular form.
-The first systems that were relatively faithful implementations of the relational model were from:
-*  University of Michigan  -- [[MICRO Relational Database Management System|Micro DBMS]] (1969)
-*  Massachusetts Institute of Technology (1971)<ref>SIGFIDET '74 Proceedings of the 1974 ACM SIGFIDET (now SIGMOD) workshop on Data description, access and control</ref>
-*  IBM UK Scientific Centre at Peterlee -- [[IBM IS1|IS1]] (1970–72) and its successor, [[PRTV]] (1973–79)
-The first system sold as an RDBMS was [[Multics Relational Data Store]] (1978). [[Ingres (database)|Ingres]] and [[IBM BS12]] followed.
-The most common definition of an RDBMS is a product that presents a view of data as a collection of rows and columns, even if it is not based strictly upon [[Relational model|relational theory]]. By this definition, RDBMS products typically implement some but not all of Codd's 12 rules.
-A second school of thought argues that if a database does not implement all of Codd's rules (or the current understanding on the relational model, as expressed by [[Christopher J Date]], [[Hugh Darwen]] and others), it is not relational. This view, shared by many theorists and other strict adherents to Codd's principles, would disqualify most DBMSs as not relational. For clarification, they often refer to some RDBMSs as ''truly-relational database management systems'' (TRDBMS), naming others ''pseudo-relational database management systems'' (PRDBMS). <!-- It can also be said as the raw database management system.-->
-As of 2009, most commercial relational DBMSs employ [[SQL]] as their [[query language]].<ref>{{cite journal | title= SRQL: Sorted Relational Query Language| last= Ramakrishnan |first=Raghu| last2=  Donjerkovic| first2=Donko| last3= Ranganathan |first3=Arvind | last4=  Beyer|first4=Kevin S.| last5= Krishnaprasad | first5=Muralidhar | journal = e Proceedings of SSDBM| year= 1998| url=http://pages.cs.wisc.edu/~beyer/papers/srql_ssdbm98.pdf}}</ref>
-Alternative query languages have been proposed and implemented, notably the pre-1996 implementation of [[QUEL query languages|Ingres QUEL]].
-==See also==
-{{Wikibooks |Structured Query Language}}
-* [[SQL]]
-* [[Object database]] (OODBMS)
-* [[Online analytical processing]] (OLAP) and [[ROLAP]] (Relational Online Analytical Processing)
-* [[Data warehouse]]
-* [[Star schema]]
-* [[Snowflake schema]]
-==References==
-{{Reflist|30em}}
-{{DEFAULTSORT:Relational Database Management System}}
-[[Category:Relational model]]
-[[Category:Relational database management systems]]
-[[de:RDBMS]]