CINXE.COM

<!DOCTYPE html> <html class="client-nojs vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-sticky-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-disabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-toc-not-available" lang="en" dir="ltr"> <head> <meta charset="UTF-8"> <title>View source for Relational database - Wikipedia</title> <script>(function(){var className="client-js vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-sticky-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-disabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-toc-not-available";var cookie=document.cookie.match(/(?:^|; )enwikimwclientpreferences=([^;]+)/);if(cookie){cookie[1].split('%2C').forEach(function(pref){className=className.replace(new RegExp('(^| )'+pref.replace(/-clientpref-\w+$|[^\w-]+/g,'')+'-clientpref-\\w+( |$)'),'$1'+pref+'$2');});}document.documentElement.className=className;}());RLCONF={"wgBreakFrames":true,"wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat": "dmy","wgMonthNames":["","January","February","March","April","May","June","July","August","September","October","November","December"],"wgRequestId":"813f328a-29d5-43ef-816e-44058eeda21a","wgCanonicalNamespace":"","wgCanonicalSpecialPageName":false,"wgNamespaceNumber":0,"wgPageName":"Relational_database","wgTitle":"Relational database","wgCurRevisionId":1260425299,"wgRevisionId":0,"wgArticleId":25873,"wgIsArticle":false,"wgIsRedirect":false,"wgAction":"edit","wgUserName":null,"wgUserGroups":["*"],"wgCategories":[],"wgPageViewLanguage":"en","wgPageContentLanguage":"en","wgPageContentModel":"wikitext","wgRelevantPageName":"Relational_database","wgRelevantArticleId":25873,"wgIsProbablyEditable":true,"wgRelevantPageIsProbablyEditable":true,"wgRestrictionEdit":[],"wgRestrictionMove":[],"wgNoticeProject":"wikipedia","wgCiteReferencePreviewsActive":false,"wgFlaggedRevsParams":{"tags":{"status":{"levels":1}}},"wgMediaViewerOnClick":true,"wgMediaViewerEnabledByDefault":true,"wgPopupsFlags":0, "wgVisualEditor":{"pageLanguageCode":"en","pageLanguageDir":"ltr","pageVariantFallbacks":"en"},"wgMFDisplayWikibaseDescriptions":{"search":true,"watchlist":true,"tagline":false,"nearby":true},"wgWMESchemaEditAttemptStepOversample":false,"wgWMEPageLength":30000,"wgRelatedArticlesCompat":[],"wgEditSubmitButtonLabelPublish":true,"wgULSPosition":"interlanguage","wgULSisCompactLinksEnabled":false,"wgVector2022LanguageInHeader":true,"wgULSisLanguageSelectorEmpty":false,"wgCheckUserClientHintsHeadersJsApi":["brands","architecture","bitness","fullVersionList","mobile","model","platform","platformVersion"],"GEHomepageSuggestedEditsEnableTopics":true,"wgGETopicsMatchModeEnabled":false,"wgGEStructuredTaskRejectionReasonTextInputEnabled":false,"wgGELevelingUpEnabledForUser":false};RLSTATE={"ext.globalCssJs.user.styles":"ready","site.styles":"ready","user.styles":"ready","ext.globalCssJs.user":"ready","user":"ready","user.options":"loading","skins.vector.search.codex.styles":"ready", "skins.vector.styles":"ready","skins.vector.icons":"ready","jquery.makeCollapsible.styles":"ready","ext.charinsert.styles":"ready","ext.wikimediamessages.styles":"ready","ext.visualEditor.desktopArticleTarget.noscript":"ready","ext.uls.interlanguage":"ready","ext.wikimediaBadges":"ready"};RLPAGEMODULES=["mediawiki.action.edit.collapsibleFooter","site","mediawiki.page.ready","jquery.makeCollapsible","skins.vector.js","ext.centralNotice.geoIP","ext.charinsert","ext.gadget.ReferenceTooltips","ext.gadget.charinsert","ext.gadget.extra-toolbar-buttons","ext.gadget.refToolbar","ext.gadget.switcher","ext.urlShortener.toolbar","ext.centralauth.centralautologin","mmv.bootstrap","ext.popups","ext.visualEditor.desktopArticleTarget.init","ext.visualEditor.targetLoader","ext.echo.centralauth","ext.eventLogging","ext.wikimediaEvents","ext.navigationTiming","ext.uls.interface","ext.cx.eventlogging.campaigns","ext.checkUser.clientHints","ext.growthExperiments.SuggestedEditSession", "wikibase.sidebar.tracking"];</script> <script>(RLQ=window.RLQ||[]).push(function(){mw.loader.impl(function(){return["user.options@12s5i",function($,jQuery,require,module){mw.user.tokens.set({"patrolToken":"+\\","watchToken":"+\\","csrfToken":"+\\"}); }];});});</script> <link rel="stylesheet" href="/w/load.php?lang=en&modules=ext.charinsert.styles%7Cext.uls.interlanguage%7Cext.visualEditor.desktopArticleTarget.noscript%7Cext.wikimediaBadges%7Cext.wikimediamessages.styles%7Cjquery.makeCollapsible.styles%7Cskins.vector.icons%2Cstyles%7Cskins.vector.search.codex.styles&only=styles&skin=vector-2022"> <script async="" src="/w/load.php?lang=en&modules=startup&only=scripts&raw=1&skin=vector-2022"></script> <meta name="ResourceLoaderDynamicStyles" content=""> <link rel="stylesheet" href="/w/load.php?lang=en&modules=site.styles&only=styles&skin=vector-2022"> <meta name="generator" content="MediaWiki 1.44.0-wmf.5"> <meta name="referrer" content="origin"> <meta name="referrer" content="origin-when-cross-origin"> <meta name="robots" content="noindex,nofollow,max-image-preview:standard"> <meta name="format-detection" content="telephone=no"> <meta name="viewport" content="width=1120"> <meta property="og:title" content="View source for Relational database - Wikipedia"> <meta property="og:type" content="website"> <link rel="preconnect" href="//upload.wikimedia.org"> <link rel="alternate" media="only screen and (max-width: 640px)" href="//en.m.wikipedia.org/wiki/Relational_database"> <link rel="alternate" type="application/x-wiki" title="Edit this page" href="/w/index.php?title=Relational_database&action=edit"> <link rel="apple-touch-icon" href="/static/apple-touch/wikipedia.png"> <link rel="icon" href="/static/favicon/wikipedia.ico"> <link rel="search" type="application/opensearchdescription+xml" href="/w/rest.php/v1/search" title="Wikipedia (en)"> <link rel="EditURI" type="application/rsd+xml" href="//en.wikipedia.org/w/api.php?action=rsd"> <link rel="canonical" href="https://en.wikipedia.org/wiki/Relational_database"> <link rel="license" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en"> <link rel="alternate" type="application/atom+xml" title="Wikipedia Atom feed" href="/w/index.php?title=Special:RecentChanges&feed=atom"> <link rel="dns-prefetch" href="//login.wikimedia.org"> </head> <body class="skin--responsive skin-vector skin-vector-search-vue mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject mw-editable page-Relational_database rootpage-Relational_database skin-vector-2022 action-edit"><a class="mw-jump-link" href="#bodyContent">Jump to content</a> <div class="vector-header-container"> <header class="vector-header mw-header"> <div class="vector-header-start"> <nav class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-dropdown" class="vector-dropdown vector-main-menu-dropdown vector-button-flush-left vector-button-flush-right" > <input type="checkbox" id="vector-main-menu-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-main-menu-dropdown" class="vector-dropdown-checkbox " aria-label="Main menu" > <label id="vector-main-menu-dropdown-label" for="vector-main-menu-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-menu mw-ui-icon-wikimedia-menu"></span> <span class="vector-dropdown-label-text">Main menu</span> </label> <div class="vector-dropdown-content"> <div id="vector-main-menu-unpinned-container" class="vector-unpinned-container"> <div id="vector-main-menu" class="vector-main-menu vector-pinnable-element"> <div class="vector-pinnable-header vector-main-menu-pinnable-header vector-pinnable-header-unpinned" data-feature-name="main-menu-pinned" data-pinnable-element-id="vector-main-menu" data-pinned-container-id="vector-main-menu-pinned-container" data-unpinned-container-id="vector-main-menu-unpinned-container" > <div class="vector-pinnable-header-label">Main menu</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-main-menu.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-main-menu.unpin">hide</button> </div> <div id="p-navigation" class="vector-menu mw-portlet mw-portlet-navigation" > <div class="vector-menu-heading"> Navigation </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-mainpage-description" class="mw-list-item"><a href="/wiki/Main_Page" title="Visit the main page [z]" accesskey="z"><span>Main page</span></a></li><li id="n-contents" class="mw-list-item"><a href="/wiki/Wikipedia:Contents" title="Guides to browsing Wikipedia"><span>Contents</span></a></li><li id="n-currentevents" class="mw-list-item"><a href="/wiki/Portal:Current_events" title="Articles related to current events"><span>Current events</span></a></li><li id="n-randompage" class="mw-list-item"><a href="/wiki/Special:Random" title="Visit a randomly selected article [x]" accesskey="x"><span>Random article</span></a></li><li id="n-aboutsite" class="mw-list-item"><a href="/wiki/Wikipedia:About" title="Learn about Wikipedia and how it works"><span>About Wikipedia</span></a></li><li id="n-contactpage" class="mw-list-item"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us" title="How to contact Wikipedia"><span>Contact us</span></a></li> </ul> </div> </div> <div id="p-interaction" class="vector-menu mw-portlet mw-portlet-interaction" > <div class="vector-menu-heading"> Contribute </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-help" class="mw-list-item"><a href="/wiki/Help:Contents" title="Guidance on how to use and edit Wikipedia"><span>Help</span></a></li><li id="n-introduction" class="mw-list-item"><a href="/wiki/Help:Introduction" title="Learn how to edit Wikipedia"><span>Learn to edit</span></a></li><li id="n-portal" class="mw-list-item"><a href="/wiki/Wikipedia:Community_portal" title="The hub for editors"><span>Community portal</span></a></li><li id="n-recentchanges" class="mw-list-item"><a href="/wiki/Special:RecentChanges" title="A list of recent changes to Wikipedia [r]" accesskey="r"><span>Recent changes</span></a></li><li id="n-upload" class="mw-list-item"><a href="/wiki/Wikipedia:File_upload_wizard" title="Add images or other media for use on Wikipedia"><span>Upload file</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> <a href="/wiki/Main_Page" class="mw-logo"> <img class="mw-logo-icon" src="/static/images/icons/wikipedia.png" alt="" aria-hidden="true" height="50" width="50"> <span class="mw-logo-container skin-invert"> <img class="mw-logo-wordmark" alt="Wikipedia" src="/static/images/mobile/copyright/wikipedia-wordmark-en.svg" style="width: 7.5em; height: 1.125em;"> <img class="mw-logo-tagline" alt="The Free Encyclopedia" src="/static/images/mobile/copyright/wikipedia-tagline-en.svg" width="117" height="13" style="width: 7.3125em; height: 0.8125em;"> </span> </a> </div> <div class="vector-header-end"> <div id="p-search" role="search" class="vector-search-box-vue vector-search-box-collapses vector-search-box-show-thumbnail vector-search-box-auto-expand-width vector-search-box"> <a href="/wiki/Special:Search" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only search-toggle" title="Search Wikipedia [f]" accesskey="f"><span class="vector-icon mw-ui-icon-search mw-ui-icon-wikimedia-search"></span> <span>Search</span> </a> <div class="vector-typeahead-search-container"> <div class="cdx-typeahead-search cdx-typeahead-search--show-thumbnail cdx-typeahead-search--auto-expand-width"> <form action="/w/index.php" id="searchform" class="cdx-search-input cdx-search-input--has-end-button"> <div id="simpleSearch" class="cdx-search-input__input-wrapper" data-search-loc="header-moved"> <div class="cdx-text-input cdx-text-input--has-start-icon"> <input class="cdx-text-input__input" type="search" name="search" placeholder="Search Wikipedia" aria-label="Search Wikipedia" autocapitalize="sentences" title="Search Wikipedia [f]" accesskey="f" id="searchInput" > <span class="cdx-text-input__icon cdx-text-input__start-icon"></span> </div> <input type="hidden" name="title" value="Special:Search"> </div> <button class="cdx-button cdx-search-input__end-button">Search</button> </form> </div> </div> </div> <nav class="vector-user-links vector-user-links-wide" aria-label="Personal tools"> <div class="vector-user-links-main"> <div id="p-vector-user-menu-preferences" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-userpage" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-dropdown" class="vector-dropdown " title="Change the appearance of the page's font size, width, and color" > <input type="checkbox" id="vector-appearance-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-appearance-dropdown" class="vector-dropdown-checkbox " aria-label="Appearance" > <label id="vector-appearance-dropdown-label" for="vector-appearance-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-appearance mw-ui-icon-wikimedia-appearance"></span> <span class="vector-dropdown-label-text">Appearance</span> </label> <div class="vector-dropdown-content"> <div id="vector-appearance-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <div id="p-vector-user-menu-notifications" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-overflow" class="vector-menu mw-portlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en" class=""><span>Donate</span></a> </li> <li id="pt-createaccount-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:CreateAccount&returnto=Relational+database&returntoquery=action%3Dedit" title="You are encouraged to create an account and log in; however, it is not mandatory" class=""><span>Create account</span></a> </li> <li id="pt-login-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:UserLogin&returnto=Relational+database&returntoquery=action%3Dedit" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o" class=""><span>Log in</span></a> </li> </ul> </div> </div> </div> <div id="vector-user-links-dropdown" class="vector-dropdown vector-user-menu vector-button-flush-right vector-user-menu-logged-out" title="Log in and more options" > <input type="checkbox" id="vector-user-links-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-user-links-dropdown" class="vector-dropdown-checkbox " aria-label="Personal tools" > <label id="vector-user-links-dropdown-label" for="vector-user-links-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-ellipsis mw-ui-icon-wikimedia-ellipsis"></span> <span class="vector-dropdown-label-text">Personal tools</span> </label> <div class="vector-dropdown-content"> <div id="p-personal" class="vector-menu mw-portlet mw-portlet-personal user-links-collapsible-item" title="User menu" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport" class="user-links-collapsible-item mw-list-item"><a href="https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en"><span>Donate</span></a></li><li id="pt-createaccount" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:CreateAccount&returnto=Relational+database&returntoquery=action%3Dedit" title="You are encouraged to create an account and log in; however, it is not mandatory"><span class="vector-icon mw-ui-icon-userAdd mw-ui-icon-wikimedia-userAdd"></span> <span>Create account</span></a></li><li id="pt-login" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:UserLogin&returnto=Relational+database&returntoquery=action%3Dedit" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o"><span class="vector-icon mw-ui-icon-logIn mw-ui-icon-wikimedia-logIn"></span> <span>Log in</span></a></li> </ul> </div> </div> <div id="p-user-menu-anon-editor" class="vector-menu mw-portlet mw-portlet-user-menu-anon-editor" > <div class="vector-menu-heading"> Pages for logged out editors <a href="/wiki/Help:Introduction" aria-label="Learn more about editing"><span>learn more</span></a> </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-anoncontribs" class="mw-list-item"><a href="/wiki/Special:MyContributions" title="A list of edits made from this IP address [y]" accesskey="y"><span>Contributions</span></a></li><li id="pt-anontalk" class="mw-list-item"><a href="/wiki/Special:MyTalk" title="Discussion about edits from this IP address [n]" accesskey="n"><span>Talk</span></a></li> </ul> </div> </div> </div> </div> </nav> </div> </header> </div> <div class="mw-page-container"> <div class="mw-page-container-inner"> <div class="vector-sitenotice-container"> <div id="siteNotice"></div> </div> <div class="vector-column-start"> <div class="vector-main-menu-container"> <div id="mw-navigation"> <nav id="mw-panel" class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-pinned-container" class="vector-pinned-container"> </div> </nav> </div> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <h1 id="firstHeading" class="firstHeading mw-first-heading">View source for Relational database</h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="This article exist only in this language. Add the article for other languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-0" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">Add languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> <div class="after-portlet after-portlet-lang"><span class="uls-after-portlet-link"></span></div> </div> </div> </div> </header> <div class="vector-page-toolbar"> <div class="vector-page-toolbar-container"> <div id="left-navigation"> <nav aria-label="Namespaces"> <div id="p-associated-pages" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-associated-pages" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-nstab-main" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/Relational_database" title="View the content page [c]" accesskey="c"><span>Article</span></a></li><li id="ca-talk" class="vector-tab-noicon mw-list-item"><a href="/wiki/Talk:Relational_database" rel="discussion" title="Discuss improvements to the content page [t]" accesskey="t"><span>Talk</span></a></li> </ul> </div> </div> <div id="vector-variants-dropdown" class="vector-dropdown emptyPortlet" > <input type="checkbox" id="vector-variants-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-variants-dropdown" class="vector-dropdown-checkbox " aria-label="Change language variant" > <label id="vector-variants-dropdown-label" for="vector-variants-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">English</span> </label> <div class="vector-dropdown-content"> <div id="p-variants" class="vector-menu mw-portlet mw-portlet-variants emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> </div> </div> </nav> </div> <div id="right-navigation" class="vector-collapsible"> <nav aria-label="Views"> <div id="p-views" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-views" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-view" class="vector-tab-noicon mw-list-item"><a href="/wiki/Relational_database"><span>Read</span></a></li><li id="ca-edit" class="selected vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Relational_database&action=edit" title="Edit this page"><span>Edit</span></a></li><li id="ca-history" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Relational_database&action=history" title="Past revisions of this page [h]" accesskey="h"><span>View history</span></a></li> </ul> </div> </div> </nav> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-dropdown" class="vector-dropdown vector-page-tools-dropdown" > <input type="checkbox" id="vector-page-tools-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-tools-dropdown" class="vector-dropdown-checkbox " aria-label="Tools" > <label id="vector-page-tools-dropdown-label" for="vector-page-tools-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">Tools</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-tools-unpinned-container" class="vector-unpinned-container"> <div id="vector-page-tools" class="vector-page-tools vector-pinnable-element"> <div class="vector-pinnable-header vector-page-tools-pinnable-header vector-pinnable-header-unpinned" data-feature-name="page-tools-pinned" data-pinnable-element-id="vector-page-tools" data-pinned-container-id="vector-page-tools-pinned-container" data-unpinned-container-id="vector-page-tools-unpinned-container" > <div class="vector-pinnable-header-label">Tools</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-page-tools.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-page-tools.unpin">hide</button> </div> <div id="p-cactions" class="vector-menu mw-portlet mw-portlet-cactions emptyPortlet vector-has-collapsible-items" title="More options" > <div class="vector-menu-heading"> Actions </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-more-view" class="vector-more-collapsible-item mw-list-item"><a href="/wiki/Relational_database"><span>Read</span></a></li><li id="ca-more-edit" class="selected vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Relational_database&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-more-history" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Relational_database&action=history"><span>View history</span></a></li> </ul> </div> </div> <div id="p-tb" class="vector-menu mw-portlet mw-portlet-tb" > <div class="vector-menu-heading"> General </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-whatlinkshere" class="mw-list-item"><a href="/wiki/Special:WhatLinksHere/Relational_database" title="List of all English Wikipedia pages containing links to this page [j]" accesskey="j"><span>What links here</span></a></li><li id="t-recentchangeslinked" class="mw-list-item"><a href="/wiki/Special:RecentChangesLinked/Relational_database" rel="nofollow" title="Recent changes in pages linked from this page [k]" accesskey="k"><span>Related changes</span></a></li><li id="t-upload" class="mw-list-item"><a href="/wiki/Wikipedia:File_Upload_Wizard" title="Upload files [u]" accesskey="u"><span>Upload file</span></a></li><li id="t-specialpages" class="mw-list-item"><a href="/wiki/Special:SpecialPages" title="A list of all special pages [q]" accesskey="q"><span>Special pages</span></a></li><li id="t-info" class="mw-list-item"><a href="/w/index.php?title=Relational_database&action=info" title="More information about this page"><span>Page information</span></a></li><li id="t-urlshortener" class="mw-list-item"><a href="/w/index.php?title=Special:UrlShortener&url=https%3A%2F%2Fen.wikipedia.org%2Fw%2Findex.php%3Ftitle%3DRelational_database%26action%3Dedit"><span>Get shortened URL</span></a></li><li id="t-urlshortener-qrcode" class="mw-list-item"><a href="/w/index.php?title=Special:QrCode&url=https%3A%2F%2Fen.wikipedia.org%2Fw%2Findex.php%3Ftitle%3DRelational_database%26action%3Dedit"><span>Download QR code</span></a></li> </ul> </div> </div> <div id="p-wikibase-otherprojects" class="vector-menu mw-portlet mw-portlet-wikibase-otherprojects" > <div class="vector-menu-heading"> In other projects </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-wikibase" class="wb-otherproject-link wb-otherproject-wikibase-dataitem mw-list-item"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q192588" title="Structured data on this page hosted by Wikidata [g]" accesskey="g"><span>Wikidata item</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> </div> </div> </div> <div class="vector-column-end"> <div class="vector-sticky-pinned-container"> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-pinned-container" class="vector-pinned-container"> </div> </nav> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-pinned-container" class="vector-pinned-container"> <div id="vector-appearance" class="vector-appearance vector-pinnable-element"> <div class="vector-pinnable-header vector-appearance-pinnable-header vector-pinnable-header-pinned" data-feature-name="appearance-pinned" data-pinnable-element-id="vector-appearance" data-pinned-container-id="vector-appearance-pinned-container" data-unpinned-container-id="vector-appearance-unpinned-container" > <div class="vector-pinnable-header-label">Appearance</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> </div> <div id="contentSub"><div id="mw-content-subtitle">← <a href="/wiki/Relational_database" title="Relational database">Relational database</a></div></div> <div id="mw-content-text" class="mw-body-content"><p>You do not have permission to edit this page, for the following reasons: </p> <ul class="permissions-errors"><li class="mw-permissionerror-blockedtext"> <div id="mw-blocked-text" style="border: 1px solid #AAA; background-color: var(--background-color-warning-subtle, ivory); color: inherit; padding: 1.5em; width: 100%; box-sizing: border-box;"> <div style="text-align: center;"><span style="font-size: 26px;"><span typeof="mw:File"><a href="/wiki/File:Stop_hand_nuvola.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/en/thumb/f/f1/Stop_hand_nuvola.svg/50px-Stop_hand_nuvola.svg.png" decoding="async" width="50" height="50" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/f/f1/Stop_hand_nuvola.svg/75px-Stop_hand_nuvola.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/f/f1/Stop_hand_nuvola.svg/100px-Stop_hand_nuvola.svg.png 2x" data-file-width="240" data-file-height="240" /></a></span><b> This IP address has been <a href="/wiki/Wikipedia:Blocking_policy" title="Wikipedia:Blocking policy">blocked</a> from <i>editing</i> Wikipedia.</b></span><br /><span style="font-size: 18px;">This does not affect your ability to <i>read</i> Wikipedia pages.</span></div><div class="paragraphbreak" style="margin-top:0.5em"></div><b>Most people who see this message have done nothing wrong.</b> Some kinds of blocks restrict editing from specific service providers or telecom companies in response to recent abuse or vandalism, and can sometimes affect other users who are unrelated to that abuse. Review the information below for assistance if you do not believe that you have done anything wrong.<div class="paragraphbreak" style="margin-top:0.5em"></div> <p>The IP address or range 8.222.128.0/17 has been <a href="/wiki/Wikipedia:Blocking_policy" title="Wikipedia:Blocking policy">blocked</a> by <a href="/wiki/User:L235" title="User:L235">‪L235‬</a> for the following reason(s): </p> <div style="padding:10px; background:var(--background-color-base, white); color:inherit; border:1px #666 solid;"> <div class="user-block colocation-webhost" style="margin-bottom: 0.5em; background-color: #ffefd5; border: 1px solid #AAA; padding: 0.7em;"> <figure class="mw-halign-left" typeof="mw:File"><span><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/53/Server-multiple.svg/40px-Server-multiple.svg.png" decoding="async" width="40" height="57" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/53/Server-multiple.svg/60px-Server-multiple.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/53/Server-multiple.svg/80px-Server-multiple.svg.png 2x" data-file-width="744" data-file-height="1052" /></span><figcaption></figcaption></figure><b>The <a href="/wiki/IP_address" title="IP address">IP address</a> that you are currently using has been blocked because it is believed to be a <a href="/wiki/Web_hosting_service" title="Web hosting service">web host provider</a> or <a href="/wiki/Colocation_centre" title="Colocation centre">colocation provider</a>.</b> To prevent abuse, <a href="/wiki/Wikipedia:Open_proxies" title="Wikipedia:Open proxies">web hosts and colocation providers may be blocked</a> from editing Wikipedia. <div style="border-top: 1px solid #AAA; clear: both">You will not be able to edit Wikipedia using a web host or colocation provider because it hides your IP address, much like a <a href="/wiki/Wikipedia:Open_proxies" title="Wikipedia:Open proxies">proxy</a> or <a href="/wiki/Virtual_private_network" title="Virtual private network">VPN</a>. <p><b>We recommend that you attempt to use another connection to edit.</b> For example, if you use a proxy or VPN to connect to the internet, turn it off when editing Wikipedia. If you edit using a mobile connection, try using a Wi-Fi connection, and vice versa. If you are using a corporate internet connection, switch to a different Wi-Fi network. If you have a Wikipedia account, please log in. </p><p>If you do not have any other way to edit Wikipedia, you will need to <a href="/wiki/Wikipedia:IP_block_exemption#Requesting_and_granting_exemption" title="Wikipedia:IP block exemption">request an IP block exemption</a>. </p> <style data-mw-deduplicate="TemplateStyles:r1214851843">.mw-parser-output .hidden-begin{box-sizing:border-box;width:100%;padding:5px;border:none;font-size:95%}.mw-parser-output .hidden-title{font-weight:bold;line-height:1.6;text-align:left}.mw-parser-output .hidden-content{text-align:left}@media all and (max-width:500px){.mw-parser-output .hidden-begin{width:auto!important;clear:none!important;float:none!important}}</style><div class="hidden-begin mw-collapsible mw-collapsed" style=""><div class="hidden-title skin-nightmode-reset-color" style="text-align:center;">How to appeal if you are confident that your connection does not use a colocation provider's IP address:</div><div class="hidden-content mw-collapsible-content" style=""> If you are confident that you are not using a web host, you may <a href="/wiki/Wikipedia:Appealing_a_block" title="Wikipedia:Appealing a block">appeal this block</a> by adding the following text on your <a href="/wiki/Help:Talk_pages" title="Help:Talk pages">talk page</a>: <code>{{<a href="/wiki/Template:Unblock" title="Template:Unblock">unblock</a>|reason=Caught by a colocation web host block but this host or IP is not a web host. My IP address is _______. <i>Place any further information here.</i> ~~~~}}</code>. <b>You must fill in the blank with your IP address for this block to be investigated.</b> Your IP address can be determined <span class="plainlinks"><b><a class="external text" href="https://en.wikipedia.org/wiki/Wikipedia:Get_my_IP_address?withJS=MediaWiki:Get-my-ip.js">here</a></b></span>. Alternatively, if you wish to keep your IP address private you can use the <a href="/wiki/Wikipedia:Unblock_Ticket_Request_System" title="Wikipedia:Unblock Ticket Request System">unblock ticket request system</a>. There are several reasons you might be editing using the IP address of a web host or colocation provider (such as if you are using VPN software or a business network); please use this method of appeal only if you think your IP address is in fact not a web host or colocation provider.</div></div> <p><span class="sysop-show" style="font-size: 85%;"><span style="border:#707070 solid 1px;background-color:#ffe0e0;padding:2px"><b>Administrators:</b></span> The <a href="/wiki/Wikipedia:IP_block_exemption" title="Wikipedia:IP block exemption">IP block exemption</a> user right should only be applied to allow users to edit using web host in exceptional circumstances, and requests should usually be directed to the functionaries team via email. If you intend to give the IPBE user right, a <a href="/wiki/Wikipedia:CheckUser" title="Wikipedia:CheckUser">CheckUser</a> needs to take a look at the account. This can be requested most easily at <a href="/wiki/Wikipedia:SPI#Quick_CheckUser_requests" class="mw-redirect" title="Wikipedia:SPI">SPI Quick Checkuser Requests</a>. <b>Unblocking</b> an IP or IP range with this template <b>is highly discouraged</b> without at least contacting the blocking administrator.</span> </p> </div></div> </div> <p>This block will expire on 18:23, 24 August 2026. Your current IP address is 8.222.208.146. </p> <div class="paragraphbreak" style="margin-top:0.5em"></div><div style="font-size: 16px;"> <p>Even when blocked, you will <i>usually</i> still be able to edit your <a href="/wiki/Special:MyTalk" title="Special:MyTalk">user talk page</a>, as well as <a href="/wiki/Wikipedia:Emailing_users" title="Wikipedia:Emailing users">email</a> administrators and other editors. </p> </div> <div class="paragraphbreak" style="margin-top:0.5em"></div><div style="font-size: 16px;"> <p>For information on how to proceed, please read the <b><a href="/wiki/Wikipedia:Appealing_a_block#Common_questions" title="Wikipedia:Appealing a block">FAQ for blocked users</a></b> and the <a href="/wiki/Wikipedia:Appealing_a_block" title="Wikipedia:Appealing a block">guideline on block appeals</a>. The <a href="/wiki/Wikipedia:Guide_to_appealing_blocks" title="Wikipedia:Guide to appealing blocks">guide to appealing blocks</a> may also be helpful. </p> </div> <p>Other useful links: <a href="/wiki/Wikipedia:Blocking_policy" title="Wikipedia:Blocking policy">Blocking policy</a> · <a href="/wiki/Help:I_have_been_blocked" title="Help:I have been blocked">Help:I have been blocked</a> </p> </div></li><li class="mw-permissionerror-globalblocking-blockedtext-range"> <div id="mw-blocked-text" style="border: 1px solid #AAA; background-color: var(--background-color-warning-subtle, ivory); color: inherit; padding: 1.5em; width: 100%; box-sizing: border-box;"> <div style="text-align: center;"><span style="font-size: 26px;"><span typeof="mw:File"><a href="/wiki/File:Stop_hand_nuvola.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/en/thumb/f/f1/Stop_hand_nuvola.svg/50px-Stop_hand_nuvola.svg.png" decoding="async" width="50" height="50" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/f/f1/Stop_hand_nuvola.svg/75px-Stop_hand_nuvola.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/f/f1/Stop_hand_nuvola.svg/100px-Stop_hand_nuvola.svg.png 2x" data-file-width="240" data-file-height="240" /></a></span><b> This IP address range has been <a href="https://meta.wikimedia.org/wiki/Global_blocks" class="extiw" title="m:Global blocks">globally blocked</a>.</b></span><br /><span style="font-size: 18px;">This does not affect your ability to <i>read</i> Wikipedia pages.</span></div><div class="paragraphbreak" style="margin-top:0.5em"></div><b>Most people who see this message have done nothing wrong.</b> Some kinds of blocks restrict editing from specific service providers or telecom companies in response to recent abuse or vandalism, and can sometimes affect other users who are unrelated to that abuse. Review the information below for assistance if you do not believe that you have done anything wrong.<div class="paragraphbreak" style="margin-top:0.5em"></div><div class="paragraphbreak" style="margin-top:0.5em"></div> <p>This block affects editing on all Wikimedia wikis. </p><p>The IP address or range 8.222.128.0/17 has been globally <a href="/wiki/Wikipedia:Blocking_policy" title="Wikipedia:Blocking policy">blocked</a> by <a href="/wiki/User:Jon_Kolbert" title="User:Jon Kolbert">‪Jon Kolbert‬</a> for the following reason(s): </p> <div style="padding:10px; background:var(--background-color-base, white); color:inherit; border:1px #666 solid;"> <p><a href="https://meta.wikimedia.org/wiki/Special:MyLanguage/NOP" class="extiw" title="m:Special:MyLanguage/NOP">Open proxy/Webhost</a>: See the <a href="https://meta.wikimedia.org/wiki/WM:OP/H" class="extiw" title="m:WM:OP/H">help page</a> if you are affected </p> </div> <p>This block will expire on 15:12, 27 August 2028. Your current IP address is 8.222.208.146. </p> <div class="paragraphbreak" style="margin-top:0.5em"></div><div style="font-size: 16px;"> <p>Even while globally blocked, you will <i>usually</i> still be able to edit pages on <a href="https://meta.wikimedia.org/wiki/" class="extiw" title="m:">Meta-Wiki</a>. </p> </div> <div class="paragraphbreak" style="margin-top:0.5em"></div><div style="font-size: 16px;"> <p>If you believe you were blocked by mistake, you can find additional information and instructions in the <a href="https://meta.wikimedia.org/wiki/Special:MyLanguage/No_open_proxies" class="extiw" title="m:Special:MyLanguage/No open proxies">No open proxies</a> global policy. Otherwise, to discuss the block please <a href="https://meta.wikimedia.org/wiki/Steward_requests/Global" class="extiw" title="m:Steward requests/Global">post a request for review on Meta-Wiki</a>. You could also send an email to the <a href="https://meta.wikimedia.org/wiki/Special:MyLanguage/Stewards" class="extiw" title="m:Special:MyLanguage/Stewards">stewards</a> <a href="https://meta.wikimedia.org/wiki/Special:MyLanguage/VRT" class="extiw" title="m:Special:MyLanguage/VRT">VRT</a> queue at <kbd>stewards@wikimedia.org</kbd> including all above details. </p> </div> <p>Other useful links: <a href="https://meta.wikimedia.org/wiki/Global_blocks" class="extiw" title="m:Global blocks">Global blocks</a> · <a href="/wiki/Help:I_have_been_blocked" title="Help:I have been blocked">Help:I have been blocked</a> </p> </div></li></ul><hr /> <div id="viewsourcetext">You can view and copy the source of this page:</div><textarea readonly="" accesskey="," id="wpTextbox1" cols="80" rows="25" style="" class="mw-editfont-monospace" lang="en" dir="ltr" name="wpTextbox1">{{Short description|Digital database whose organization is based on the relational model of data}} {{more citations needed| date=January 2024| reason=some refs but tech article needs more}} A '''relational database''' ('''RDB'''<ref>{{Cite conference |title=Portable Software Tools for Managing and Referencing Taxonomies |conference=Digital Mapping Techniques '03 Workshop Proceedings|at=2. Relational Database Technology and Taxonomic Representation |date=2003 |url=https://pubs.usgs.gov/of/2003/of03-471/hastings/index.html |conference-url=https://pubs.usgs.gov/of/2003/of03-471/ |last=Hastings |first=Jordan |volume=U.S. Geological Survey Open-File Report 03–471 |access-date=2024-04-06 |url-status=live |archive-url=https://web.archive.org/web/20141021070621/https://pubs.usgs.gov/of/2003/of03-471/hastings/index.html |archive-date=2014-10-21 |via=[[United States Geological Survey]]}}</ref>) is a [[database]] based on the [[relational model]] of data, as proposed by [[E. F. Codd]] in 1970.<ref name=codd/> A [[DBMS|database management system]] used to maintain relational databases is a '''relational database management system''' ('''RDBMS'''). Many relational database systems are equipped with the option of using [[SQL]] (Structured Query Language) for querying and updating the database.<ref>{{cite web |last=Ambler |first=Scott |title=Relational Databases 101: Looking at the Whole Picture |date=21 March 2023 |url=http://www.agiledata.org/essays/relationalDatabases.html }}{{better source needed|date=June 2018}}</ref> ==History== The concept of relational database was defined by [[Edgar F. Codd|E. F. Codd]] at [[IBM]] in 1970. Codd introduced the term ''relational'' in his research paper "A Relational Model of Data for Large Shared Data Banks".<ref name="codd" /> In this paper and later papers, he defined what he meant by ''relation''. One well-known definition of what constitutes a relational database system is composed of [[Codd's 12 rules]]. However, no commercial implementations of the relational model conform to all of Codd's rules,<ref>{{cite book |last=Date |first=Chris |title=Database in depth: relational theory for practitioners |date=5 May 2005 |publisher=O'Reilly |isbn=0-596-10012-4}}</ref> so the term has gradually come to describe a broader class of database systems, which at a minimum: # Present the data to the user as [[relation (database)|relations]] (a presentation in tabular form, i.e. as a ''collection'' of [[table (database)|tables]] with each table consisting of a set of [[Row (database)|rows]] and [[Column (database)|columns]]); # Provide [[relational operator]]s to manipulate the data in tabular form. In 1974, IBM began developing [[IBM System R|System R]], a research project to develop a prototype RDBMS.<ref> {{cite book |date=8 Jan 1999 |title=Funding a Revolution: Government Support for Computing Research |publisher=National Academies Press |isbn=0309062780 |url={{google books |plainurl=y |id=wvCbAgAAQBAJ}} }}</ref><ref>{{cite book |last1=Sumathi |first1=S. |last2=Esakkirajan |first2=S. |date=13 Feb 2008 |title=Fundamentals of Relational Database Management Systems |publisher=Springer |isbn=978-3540483977 |quote=The product was called SQL/DS (Structured Query Language/Data Store) and ran under the DOS/VSE operating system environment}}</ref> The first system sold as an RDBMS was [[Multics Relational Data Store]] (June 1976).{{citation needed|reason=Due to significance of nature of claim specific unambiguous cite is required at this point|date=August 2020}} [[Oracle Database|Oracle]] was released in 1979 by Relational Software, now [[Oracle Corporation]].<ref>{{cite journal |date=May 2007 |title=Oracle Timeline |journal=Profit Magazine |publisher=Oracle |volume=12 |issue=2 |page=26 |url=http://www.oracle.com/us/corporate/profit/p27anniv-timeline-151918.pdf |access-date=2013-05-16}}</ref> [[Ingres (database)|Ingres]] and [[IBM BS12]] followed. Other examples of an RDBMS include [[IBM Db2]], [[Adaptive Server Enterprise|SAP Sybase ASE]], and [[IBM Informix|Informix]]. In 1984, the first RDBMS for [[Macintosh 128K|Macintosh]] began being developed, code-named Silver Surfer, and was released in 1987 as [[4th Dimension (Software)|4th Dimension]] and known today as 4D.<ref>{{cite web |title=New Database Software Program Moves Macintosh Into The Big Leagues |website=tribunedigital-chicagotribune |date=28 June 1987 |url=https://www.chicagotribune.com/1987/06/28/new-database-software-program-moves-macintosh-into-the-big-leagues/ |access-date=2016-03-17}}</ref> 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)<ref name=ST_1>{{cite journal| title=A set theoretic data structure and retrieval language| author1=Hershey, W.R.| author2=Easthope, C.H.| url=https://dl.acm.org/doi/10.1145/1095495.1095500| publisher=[[Association for Computing Machinery]]| journal=ACM SIGIR Forum| volume=7| issue=4| pages=45–55| date=1 December 1972| access-date=4 January 2024| doi=10.1145/1095495.1095500}}</ref> * Massachusetts Institute of Technology (1971)<ref name=SIG_1>{{cite book| title=SIGFIDET '74: Proceedings of the 1974 ACM SIGFIDET (Now SIGMOD) Workshop on Data Description, Access and Control: Data Models: Data-Structure-Set versus Relational| url=https://dl.acm.org/doi/book/10.1145/800297| publisher=[[Association for Computing Machinery]]| date=1 January 1975| doi=10.1145/800297| access-date=4 January 2024| isbn=978-1-4503-7418-7}}</ref> * IBM UK Scientific Centre at Peterlee – [[IBM IS1|IS1]] (1970–72),<ref name=PS_1>{{cite book| title=The Peterlee IS/1 System| author=Notley, M.G.| url=https://scholar.google.com/scholar?lookup=0&q=NOTLEY,+M.G.+The+Peterlee+IS/1+System,+I.B.M.+(U.K.)+Scientific+Centre+Report,+March+1972.+UKSC-0018.&hl=en&as_sdt=0,5| publisher=IBM United Kingdom Scientific Centre| date=1972| access-date=4 January 2024}}</ref> and its successor, [[PRTV]] (1973–79).<ref name="Todd 1976">{{cite journal|title=The Peterlee Relational Test Vehicle - A System Overview|journal=IBM Systems Journal|year=1976|first=Stephen|last=Todd|volume=15|issue=4|pages=285–308|doi=10.1147/sj.154.0285}}</ref> 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).{{citation needed| reason=no references|date=January 2024}}  As of 2009, most commercial relational DBMSs employ [[SQL]] as their [[query language]].<ref>{{cite journal |last1=Ramakrishnan |first1=Raghu |last2=Donjerkovic |first2=Donko |last3=Ranganathan |first3=Arvind |last4=Beyer |first4=Kevin S. |last5=Krishnaprasad |first5=Muralidhar |year=1998 |title=SRQL: Sorted Relational Query Language |journal=E Proceedings of SSDBM |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]]. ==Relational model== {{Main|Relational model}} A relational model organizes data into one or more [[table (database)|tables]] (or "relations") of [[Column (database)|columns]] and [[row (database)|rows]], with a [[unique key]] identifying each row. Rows are also called [[Record (computer science)|records]] or [[tuple]]s.<ref>{{cite web |title=A Relational Database Overview |website=oracle.com |url=https://docs.oracle.com/javase/tutorial/jdbc/overview/database.html}}</ref> Columns are also called attributes. Generally, each table/relation represents one "entity type" (such as customer or product). The rows represent instances of that type of [[entity]] (such as "Lee" or "chair") and the columns represent values attributed to that instance (such as address or price). For example, each row of a class table corresponds to a class, and a class corresponds to multiple students, so the relationship between the class table and the student table is "one to many"<ref>{{Citation |date=1992 |title=A universal relation model for a nested database |work=The Nested Universal Relation Database Model |series=Lecture Notes in Computer Science |volume=595 |pages=109–135 |place=Berlin, Heidelberg |publisher=Springer Berlin Heidelberg |doi=10.1007/3-540-55493-9_5 |isbn=978-3-540-55493-6 |url=http://dx.doi.org/10.1007/3-540-55493-9_5 |access-date=2020-11-01}}</ref> ==Keys== Each row in a table has its own unique key. 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 key]]s). Codd showed that data relationships of arbitrary complexity can be represented by a simple set of concepts.<ref name="codd" /> Part of this processing involves consistently being able to select or modify one and only one row in a table. Therefore, most physical implementations have a unique [[primary key]] (PK) for each row in a table. When a new row is written to the table, a new unique value for the primary key is generated; this is the key that the system uses primarily for accessing the table. System performance is optimized for PKs. Other, more [[natural key]]s may also be identified and defined as [[alternate key]]s (AK). Often several columns are needed to form an AK (this is one reason why a single integer column is usually made the PK). Both PKs and AKs have the ability to uniquely identify a row within a table. Additional technology may be applied to ensure a unique ID across the world, a [[globally unique identifier]], when there are broader system requirements. The primary keys within a database are used to define the relationships among the tables. When a PK migrates to another table, it becomes a foreign key (FK) in the other table. 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 (data model)|one-to-one]] or [[One-to-many (data model)|one-to-many]] relationship. Most relational database designs resolve [[Many-to-many (data model)|many-to-many]] relationships by creating an additional table that contains the PKs from both of the other entity tables{{snd}} the relationship becomes an entity; the resolution table is then named appropriately and the two FKs are combined to form a PK. The migration of PKs to other tables is the second major reason why system-assigned integers are used normally as PKs; there is usually neither efficiency nor clarity in migrating a bunch of other types of columns. ===Relationships=== Relationships are a logical connection between different tables (entities), established on the basis of interaction among these tables. These relationships can be modelled as an [[Entity–relationship model|entity-relationship model]]. ==Transactions== In order for a database management system (DBMS) to operate efficiently and accurately, it must use [[ACID transactions]].<ref>{{ cite web |date=1998-11-23 |title=Gray to be Honored With A. M. Turing Award This Spring |publisher= Microsoft PressPass |url=http://www.microsoft.com/presspass/features/1998/11-23gray.mspx |access-date=2009-01-16 |url-status=live |archive-url=https://web.archive.org/web/20090206084720/http://www.microsoft.com/presspass/features/1998/11-23gray.mspx |archive-date=6 February 2009}}</ref><ref>{{cite conference |first=Jim |last=Gray |author-link=Jim Gray (computer scientist) |title=The Transaction Concept: Virtues and Limitations |book-title=Proceedings of the 7th International Conference on Very Large Databases |pages=144–154 |publisher=[[Tandem Computers]] |date=September 1981 |location=Cupertino, CA |url=http://research.microsoft.com/~gray/papers/theTransactionConcept.pdf |access-date=2006-11-09}}</ref><ref>Gray, Jim, and Reuter, Andreas, ''Distributed Transaction Processing: Concepts and Techniques''. [[Morgan Kaufmann]], 1993. {{ISBN|1-55860-190-2}}.</ref> ==Stored procedures== Part of the programming within a RDBMS is accomplished using [[stored procedure]]s (SPs). Often procedures can be used to greatly reduce the amount of information transferred within and outside of a system. For increased security, the system design may grant access to only the stored procedures and not directly to the tables. Fundamental stored procedures contain the logic needed to insert new and update existing data. More complex procedures may be written to implement additional rules and logic related to processing or selecting the data. ==Terminology== [[Image:Relational database terms.svg|350px|thumb|right|Relational database terminology]] The relational database was first defined in June 1970 by [[Edgar F. Codd|Edgar Codd]], of IBM's [[IBM Almaden Research Center|San Jose Research Laboratory]].<ref name="codd">{{cite journal |last=Codd |first=E. F. |author-link=Edgar F. Codd |year=1970 |title=A Relational Model of Data for Large Shared Data Banks |journal=[[Communications of the ACM]] |doi=10.1145/362384.362685 |volume=13 |number=6 |pages=377–387|s2cid=207549016 |doi-access=free }}</ref> Codd's view of what qualifies as an RDBMS is summarized in [[Codd's 12 rules]]. 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: {| class="wikitable" |- ! SQL term ! Relational database term ! Description |- | [[Row (database)|'''''Row''''']] | '''''[[Tuple]]''''' or [[Record (computer science)|'''''record''''']] | A data set representing a single item |- | [[Column (database)|'''''Column''''']] | '''''Attribute''''' or '''''field''''' | A labeled element of a tuple, e.g. "Address" or "Date of birth" |- | [[Table (database)|'''''Table''''']] | [[Relation (database)|'''''Relation''''']] or [[relvar|'''''Base relvar''''']] | A set of tuples sharing the same attributes; a set of columns and rows |- | [[View (SQL)|'''''View''''']] or '''''[[result set]]''''' | '''''Derived relvar''''' | Any set of tuples; a data report from the RDBMS in response to a [[query language|query]] |} ==Relations or tables== {{Main|Relation (database)|Table (database)}} In a relational database, a ''[[relation (database)|relation]]'' is a set of [[tuple]]s that have the same [[Attribute (computing)|attributes]]. A tuple usually represents an object and information about that object. Objects are typically physical objects or concepts. A relation is usually described as a [[Table (database)|table]], which is organized into [[Row (database)|rows]] and [[Column (database)|columns]]. All the data referenced by an attribute are in the same [[data domain|domain]] and conform to the same constraints. The relational model specifies that the tuples of a relation have no specific order and that the tuples, in turn, impose no order on the attributes. Applications access data by specifying queries, which use operations such as ''select'' to identify tuples, ''project'' to identify attributes, and ''join'' to combine relations. Relations can be modified using the ''insert'', ''delete'', and ''update'' operators. New tuples can supply explicit values or be derived from a query. Similarly, queries identify tuples for updating or deleting. Tuples by definition are unique. If the tuple contains a [[candidate key|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. The definition of a tuple requires that it be unique, but does not require a primary key to be defined. Because a tuple is unique, its attributes by definition constitute a [[superkey]]. ==Base and derived relations== {{Main|Relvar|View (database)}} All data are stored and accessed via [[relation (database)|relations]]. Relations that store data are called "base relations", and in implementations are called "tables". Other relations do not store data, but are computed by applying relational operations to other relations. These relations are sometimes called "derived relations". In implementations these are called "[[View (database)|views]]" or "queries". Derived relations are convenient in that they act as a single relation, even though they may grab information from several relations. Also, derived relations can be used as an [[abstraction layer]]. ===Domain=== {{Main|Data domain}} A domain describes the set of possible values for a given attribute, and can be considered a constraint on the value of the attribute. Mathematically, attaching a domain to an attribute means that any value for the attribute must be an element of the specified set. The character string ''"ABC"'', for instance, is not in the integer domain, but the integer value ''123'' is. Another example of domain describes the possible values for the field "CoinFace" as ("Heads","Tails"). So, the field "CoinFace" will not accept input values like (0,1) or (H,T). ==Constraints== Constraints are often used to make it possible to further restrict the domain of an attribute. For instance, a constraint can restrict a given integer attribute to values between 1 and 10. Constraints provide one method of implementing [[business rules]] in the database and support subsequent data use within the application layer. SQL implements constraint functionality in the form of [[check constraint]]s. Constraints restrict the data that can be stored in [[relation (database)|relations]]. These are usually defined using expressions that result in a [[Boolean data type|Boolean]] value, indicating whether or not the data satisfies the constraint. Constraints can apply to single attributes, to a tuple (restricting combinations of attributes) or to an entire relation. Since every attribute has an associated domain, there are constraints ('''domain constraints'''). The two principal rules for the relational model are known as '''[[entity integrity]]''' and '''[[referential integrity]]'''. ===Primary key=== {{Main|Unique key|Primary key}} Every [[Relation (database)|relation]]/table has a primary key, this being a consequence of a relation being a [[Set (mathematics)|set]].{{Sfnp|Date|1984|p=268}} A primary key uniquely specifies a tuple within a table. While natural attributes (attributes used to describe the data being entered) are sometimes good primary keys, [[surrogate key]]s are often used instead. A surrogate key is an artificial attribute assigned to an object which uniquely identifies it (for instance, in a table of information about students at a school they might all be assigned a student ID in order to differentiate them). The surrogate key has no intrinsic (inherent) meaning, but rather is useful through its ability to uniquely identify a tuple. Another common occurrence, especially in regard to N:M cardinality is the [[Compound key|composite key]]. A composite key is a key made up of two or more attributes within a table that (together) uniquely identify a record.<ref>{{Cite book |last1=Connolly |first1=Thomas M |title=Database systems: a practical approach to design, implementation, and management |last2=Begg |first2=Carolyn E |publisher=Pearson |year=2015 |isbn=978-1-292-06118-4 |edition=global |location=Boston Columbus Indianapolis |pages=416}}</ref> ===Foreign key=== {{Main|Foreign key}} Foreign key refers to a field in a relational table that matches the primary key column of another table. It relates the two keys. Foreign keys need not have unique values in the referencing relation. A foreign key can be used to [[cross-reference]] tables, and it effectively uses the values of attributes in the referenced relation to restrict the domain of one or more attributes in the referencing relation. The concept is described formally as: "For all tuples in the referencing relation projected over the referencing attributes, there must exist a tuple in the referenced relation projected over those same attributes such that the values in each of the referencing attributes match the corresponding values in the referenced attributes." ===Stored procedures=== {{Main|Stored procedure}} A stored procedure is executable code that is associated with, and generally stored in, the database. Stored procedures usually collect and customize common operations, like inserting a [[tuple]] into a [[relation (database)|relation]], gathering statistical information about usage patterns, or encapsulating complex [[business logic]] and calculations. Frequently they are used as an [[application programming interface]] (API) for security or simplicity. Implementations of stored procedures on SQL RDBMS's often allow developers to take advantage of [[Procedural programming|procedural]] extensions (often vendor-specific) to the standard [[Declarative programming|declarative]] SQL syntax. Stored procedures are not part of the relational database model, but all commercial implementations include them. ===Index=== {{Main|Index (database)}} An index is one way of providing quicker access to data. Indices can be created on any combination of attributes on a [[relation (database)|relation]]. Queries that filter using those attributes can find matching tuples directly using the index (similar to [[Hash table]] lookup), without having to check each tuple in turn. This is analogous to using the [[Index (publishing)|index of a book]] to go directly to the page on which the information you are looking for is found, so that you do not have to read the entire book to find what you are looking for. Relational databases typically supply multiple indexing techniques, each of which is optimal for some combination of data distribution, relation size, and typical access pattern. Indices are usually implemented via [[B+ tree]]s, [[R-tree]]s, and [[Bitmap index|bitmaps]]. Indices are usually not considered part of the database, as they are considered an implementation detail, though indices are usually maintained by the same group that maintains the other parts of the database. The use of efficient indexes on both primary and foreign keys can dramatically improve query performance. This is because B-tree indexes result in query times proportional to log(n) where n is the number of rows in a table and hash indexes result in constant time queries (no size dependency as long as the relevant part of the index fits into memory). ==Relational operations== {{Main|Relational algebra}} Queries made against the relational database, and the derived [[relvars]] in the database are expressed in a [[relational calculus]] or a [[relational algebra]]. In his original relational algebra, Codd introduced eight relational operators in two groups of four operators each. The first four operators were based on the traditional mathematical [[Set theory|set operations]]: * The [[Union (set theory)|union]] operator (υ) combines the tuples of two [[relation (database)|relations]] and removes all duplicate tuples from the result. The relational union operator is equivalent to the [[Union (SQL)|SQL UNION]] operator. * The [[Intersection (set theory)|intersection]] operator (∩) produces the set of tuples that two relations share in common. Intersection is implemented in SQL in the form of the [[Intersect (SQL)|INTERSECT]] operator. * The [[Complement (set theory)|set difference]] operator (-) acts on two relations and produces the set of tuples from the first relation that do not exist in the second relation. Difference is implemented in SQL in the form of the [[Except (SQL)|EXCEPT]] or MINUS operator. * The [[cartesian product]] (X) of two relations is a join that is not restricted by any criteria, resulting in every tuple of the first relation being matched with every tuple of the second relation. The cartesian product is implemented in SQL as the [[Cross join]] operator. The remaining operators proposed by Codd involve special operations specific to relational databases: * The selection, or restriction, operation (σ) retrieves tuples from a relation, limiting the results to only those that meet a specific criterion, i.e. a [[subset]] in terms of set theory. The SQL equivalent of selection is the [[Select (SQL)|SELECT]] query statement with a [[Where (SQL)|WHERE]] clause. * The [[Projection (relational algebra)|projection operation]] (π) extracts only the specified attributes from a tuple or set of tuples. * The join operation defined for relational databases is often referred to as a natural join (⋈). In this type of join, two relations are connected by their common attributes. MySQL's approximation of a natural join is the [[Inner join]] operator. In SQL, an INNER JOIN prevents a cartesian product from occurring when there are two tables in a query. For each table added to a SQL Query, one additional INNER JOIN is added to prevent a cartesian product. Thus, for N tables in an SQL query, there must be N−1 INNER JOINS to prevent a cartesian product. * The [[Relational algebra#Division|relational division]] (÷) operation is a slightly more complex operation and essentially involves using the tuples of one relation (the dividend) to partition a second relation (the divisor). The relational division operator is effectively the opposite of the cartesian product operator (hence the name). Other operators have been introduced or proposed since Codd's introduction of the original eight including relational comparison operators and extensions that offer support for nesting and hierarchical data, among others. ==Normalization== {{Main|Database normalization}} Normalization was first proposed by Codd as an integral part of the relational model. It encompasses a set of procedures designed to eliminate non-simple domains (non-atomic values) and the redundancy (duplication) of data, which in turn prevents data manipulation anomalies and loss of data integrity. The most common forms of normalization applied to databases are called the [[Database normalization#Normal forms|normal forms]]. ==RDBMS== [[File:RDBMS structure.png|thumbnail|right|The general structure of a relational database]] {{See also|Database#Database management system}} Connolly and Begg define database management system (DBMS) as a "software system that enables users to define, create, maintain and control access to the database".<ref name="Begg-p64">{{cite book |last1=Connolly |first1=Thomas M. |last2=Begg |first2=Carolyn E. |date=2014 |title=Database Systems – A Practical Approach to Design Implementation and Management |edition=6th |publisher=Pearson |isbn=978-1292061184 |page=64}}</ref> RDBMS is an extension of that initialism that is sometimes used when the underlying database is relational. An alternative definition for a ''relational database management system'' is a database management system (DBMS) based on the [[relational model]]. Most databases in widespread use today are based on this model.<ref>{{cite book |last1=Pratt |first1=Philip J. |last2=Last |first2=Mary Z. |date=2014-09-08 |title=Concepts of Database Management |edition=8 |publisher=Course Technology |isbn=9781285427102 |page=29 }}</ref> RDBMSs have been a common option 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 RDBMS were easier to implement and administer. Nonetheless, relational stored data 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.<ref>{{Cite book |last=Feuerlich |first=George |url=https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=a61bad77f48d8438f47393c720292f5dc33a4c0d#page=169 |title=Dateso 10; Database Trends and Directions: Current Challenges and Opportunities |date=21 April 2010 |publisher=MATFYZPRESS |year=2010 |isbn=978-80-7378-116-3 |edition=1st |location=Prague, Sokolovsk |pages=163–174}}</ref> 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 |title=NoSQL databases eat into the relational database market |date=4 March 2015 |url=https://www.techrepublic.com/article/nosql-databases-eat-into-the-relational-database-market |access-date=2018-03-14}}</ref> ==Distributed relational databases== [[DRDA|Distributed Relational Database Architecture]] (DRDA) was designed by a workgroup within IBM in the period 1988 to 1994. DRDA enables network connected relational databases to cooperate to fulfill SQL requests.<ref>{{cite journal |last1=Reinsch |first1=R. |date=1988 |title=Distributed database for SAA |journal=IBM Systems Journal |volume=27 |issue=3 |pages=362–389 |doi=10.1147/sj.273.0362}}</ref><ref>{{cite book |date=1990 |title=Distributed Relational Database Architecture Reference |publisher=IBM Corp. SC26-4651-0}}</ref> The messages, protocols, and structural components of DRDA are defined by the [[Distributed Data Management Architecture]]. ==List of database engines== According to [[DB-Engines ranking|DB-Engines]], in January 2023 the most popular systems on the db-engines.com web site were:<ref>{{cite web | title=DB-Engines Ranking of Relational DBMS | website=DB-Engines | url=https://db-engines.com/en/ranking/relational+dbms | access-date=2022-04-29}}</ref> # [[Oracle Database]] # [[MySQL]] # [[Microsoft SQL Server]] # [[PostgreSQL]] (free software) # [[IBM Db2]] # [[Microsoft Access]] # [[SQLite]] (free software) # [[MariaDB]] (free software)  # [[Snowflake Inc.|Snowflake]] # [[Microsoft Azure SQL Database]] # [[Apache Hive]] (free software) # [[Teradata|Teradata Vantage]] 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 |date=2012-04-12 |title=Oracle the clear leader in $24 billion RDBMS market |url=http://itknowledgeexchange.techtarget.com/eye-on-oracle/oracle-the-clear-leader-in-24-billion-rdbms-market/ |access-date=2013-03-01}}</ref> ==See also== * [[Comparison of relational database management systems]] * [[Datalog]] * [[Data warehouse]] * [[List of relational database management systems]] * [[Object database]] (OODBMS) * [[Online analytical processing]] (OLAP) and [[ROLAP]] (Relational Online Analytical Processing) * [[Relational transducer]] * [[Snowflake schema]] * [[SQL]] * [[Star schema]] ==References== {{Reflist}} ==Sources== *{{cite book |last=Date |first=C. J. |author-link=Christopher J. Date |date=1984 |title=A Guide to DB2 |edition=student |publisher=[[Addison-Wesley]] |isbn=0201113171 |ol=OL2838595M |oclc=256383726 |url=https://archive.org/details/guidetodb2users00date}} {{Wikibooks |Structured Query Language}} {{Databases}} {{Authority control}} [[Category:Relational model]] [[Category:Database theory]] [[Category:Types of databases]] [[Category:English inventions]] [[Category:Computer-related introductions in 1969]] [[Category:Relational database management systems| ]] </textarea><div class="templatesUsed"><div class="mw-templatesUsedExplanation"><p><span id="templatesused">Pages transcluded onto the current version of this page<span class="posteditwindowhelplinks"> (<a href="/wiki/Help:Transclusion" title="Help:Transclusion">help</a>)</span>:</span> </p></div><ul> <li><a href="/wiki/Template:Ambox" title="Template:Ambox">Template:Ambox</a> (<a href="/w/index.php?title=Template:Ambox&action=edit" title="Template:Ambox">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Authority_control" title="Template:Authority control">Template:Authority control</a> (<a href="/w/index.php?title=Template:Authority_control&action=edit" title="Template:Authority control">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Better_source_needed" title="Template:Better source needed">Template:Better source needed</a> (<a href="/w/index.php?title=Template:Better_source_needed&action=edit" title="Template:Better source needed">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Catalog_lookup_link" title="Template:Catalog lookup link">Template:Catalog lookup link</a> (<a href="/w/index.php?title=Template:Catalog_lookup_link&action=edit" title="Template:Catalog lookup link">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Category_handler" title="Template:Category handler">Template:Category handler</a> (<a href="/w/index.php?title=Template:Category_handler&action=edit" title="Template:Category handler">view source</a>) (protected)</li><li><a href="/wiki/Template:Citation" title="Template:Citation">Template:Citation</a> (<a href="/w/index.php?title=Template:Citation&action=edit" title="Template:Citation">view source</a>) (protected)</li><li><a href="/wiki/Template:Citation_needed" title="Template:Citation needed">Template:Citation needed</a> (<a href="/w/index.php?title=Template:Citation_needed&action=edit" title="Template:Citation needed">view source</a>) (protected)</li><li><a href="/wiki/Template:Cite_book" title="Template:Cite book">Template:Cite book</a> (<a href="/w/index.php?title=Template:Cite_book&action=edit" title="Template:Cite book">view source</a>) (protected)</li><li><a href="/wiki/Template:Cite_conference" title="Template:Cite conference">Template:Cite conference</a> (<a href="/w/index.php?title=Template:Cite_conference&action=edit" title="Template:Cite conference">view source</a>) (protected)</li><li><a href="/wiki/Template:Cite_journal" title="Template:Cite journal">Template:Cite journal</a> (<a href="/w/index.php?title=Template:Cite_journal&action=edit" title="Template:Cite journal">view source</a>) (protected)</li><li><a href="/wiki/Template:Cite_web" title="Template:Cite web">Template:Cite web</a> (<a href="/w/index.php?title=Template:Cite_web&action=edit" title="Template:Cite web">view source</a>) (protected)</li><li><a href="/wiki/Template:Databases" title="Template:Databases">Template:Databases</a> (<a href="/w/index.php?title=Template:Databases&action=edit" title="Template:Databases">edit</a>) </li><li><a href="/wiki/Template:Delink" title="Template:Delink">Template:Delink</a> (<a href="/w/index.php?title=Template:Delink&action=edit" title="Template:Delink">view source</a>) (protected)</li><li><a href="/wiki/Template:Find_sources_mainspace" title="Template:Find sources mainspace">Template:Find sources mainspace</a> (<a href="/w/index.php?title=Template:Find_sources_mainspace&action=edit" title="Template:Find sources mainspace">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Fix" title="Template:Fix">Template:Fix</a> (<a href="/w/index.php?title=Template:Fix&action=edit" title="Template:Fix">view source</a>) (protected)</li><li><a href="/wiki/Template:Fix/category" title="Template:Fix/category">Template:Fix/category</a> (<a href="/w/index.php?title=Template:Fix/category&action=edit" title="Template:Fix/category">view source</a>) (protected)</li><li><a href="/wiki/Template:Google_books" title="Template:Google books">Template:Google books</a> (<a href="/w/index.php?title=Template:Google_books&action=edit" title="Template:Google books">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Hlist/styles.css" title="Template:Hlist/styles.css">Template:Hlist/styles.css</a> (<a href="/w/index.php?title=Template:Hlist/styles.css&action=edit" title="Template:Hlist/styles.css">view source</a>) (protected)</li><li><a href="/wiki/Template:ISBN" title="Template:ISBN">Template:ISBN</a> (<a href="/w/index.php?title=Template:ISBN&action=edit" title="Template:ISBN">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Icon" title="Template:Icon">Template:Icon</a> (<a href="/w/index.php?title=Template:Icon&action=edit" title="Template:Icon">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Main" title="Template:Main">Template:Main</a> (<a href="/w/index.php?title=Template:Main&action=edit" title="Template:Main">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Main_other" title="Template:Main other">Template:Main other</a> (<a href="/w/index.php?title=Template:Main_other&action=edit" title="Template:Main other">view source</a>) (protected)</li><li><a href="/wiki/Template:More_citations_needed" title="Template:More citations needed">Template:More citations needed</a> (<a href="/w/index.php?title=Template:More_citations_needed&action=edit" title="Template:More citations needed">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Navbox" title="Template:Navbox">Template:Navbox</a> (<a href="/w/index.php?title=Template:Navbox&action=edit" title="Template:Navbox">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Pagetype" title="Template:Pagetype">Template:Pagetype</a> (<a href="/w/index.php?title=Template:Pagetype&action=edit" title="Template:Pagetype">view source</a>) (protected)</li><li><a href="/wiki/Template:Plainlist/styles.css" title="Template:Plainlist/styles.css">Template:Plainlist/styles.css</a> (<a href="/w/index.php?title=Template:Plainlist/styles.css&action=edit" title="Template:Plainlist/styles.css">view source</a>) (protected)</li><li><a href="/wiki/Template:Reflist" title="Template:Reflist">Template:Reflist</a> (<a href="/w/index.php?title=Template:Reflist&action=edit" title="Template:Reflist">view source</a>) (protected)</li><li><a href="/wiki/Template:Reflist/styles.css" title="Template:Reflist/styles.css">Template:Reflist/styles.css</a> (<a href="/w/index.php?title=Template:Reflist/styles.css&action=edit" title="Template:Reflist/styles.css">view source</a>) (protected)</li><li><a href="/wiki/Template:SDcat" title="Template:SDcat">Template:SDcat</a> (<a href="/w/index.php?title=Template:SDcat&action=edit" title="Template:SDcat">view source</a>) (protected)</li><li><a href="/wiki/Template:See_also" title="Template:See also">Template:See also</a> (<a href="/w/index.php?title=Template:See_also&action=edit" title="Template:See also">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Sfnp" title="Template:Sfnp">Template:Sfnp</a> (<a href="/w/index.php?title=Template:Sfnp&action=edit" title="Template:Sfnp">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Short_description" title="Template:Short description">Template:Short description</a> (<a href="/w/index.php?title=Template:Short_description&action=edit" title="Template:Short description">view source</a>) (protected)</li><li><a href="/wiki/Template:Short_description/lowercasecheck" title="Template:Short description/lowercasecheck">Template:Short description/lowercasecheck</a> (<a href="/w/index.php?title=Template:Short_description/lowercasecheck&action=edit" title="Template:Short description/lowercasecheck">view source</a>) (protected)</li><li><a href="/wiki/Template:Side_box" title="Template:Side box">Template:Side box</a> (<a href="/w/index.php?title=Template:Side_box&action=edit" title="Template:Side box">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Sister_project" title="Template:Sister project">Template:Sister project</a> (<a href="/w/index.php?title=Template:Sister_project&action=edit" title="Template:Sister project">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Sister_project/styles.css" title="Template:Sister project/styles.css">Template:Sister project/styles.css</a> (<a href="/w/index.php?title=Template:Sister_project/styles.css&action=edit" title="Template:Sister project/styles.css">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Snd" class="mw-redirect" title="Template:Snd">Template:Snd</a> (<a href="/w/index.php?title=Template:Snd&action=edit" class="mw-redirect" title="Template:Snd">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Spaced_en_dash" title="Template:Spaced en dash">Template:Spaced en dash</a> (<a href="/w/index.php?title=Template:Spaced_en_dash&action=edit" title="Template:Spaced en dash">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Tooltip" title="Template:Tooltip">Template:Tooltip</a> (<a href="/w/index.php?title=Template:Tooltip&action=edit" title="Template:Tooltip">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Tooltip/styles.css" title="Template:Tooltip/styles.css">Template:Tooltip/styles.css</a> (<a href="/w/index.php?title=Template:Tooltip/styles.css&action=edit" title="Template:Tooltip/styles.css">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Trim" title="Template:Trim">Template:Trim</a> (<a href="/w/index.php?title=Template:Trim&action=edit" title="Template:Trim">view source</a>) (protected)</li><li><a href="/wiki/Template:Wikibooks" title="Template:Wikibooks">Template:Wikibooks</a> (<a href="/w/index.php?title=Template:Wikibooks&action=edit" title="Template:Wikibooks">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Yesno" title="Template:Yesno">Template:Yesno</a> (<a href="/w/index.php?title=Template:Yesno&action=edit" title="Template:Yesno">view source</a>) (protected)</li><li><a href="/wiki/Template:Yesno-no" title="Template:Yesno-no">Template:Yesno-no</a> (<a href="/w/index.php?title=Template:Yesno-no&action=edit" title="Template:Yesno-no">view source</a>) (template editor protected)</li><li><a href="/wiki/Template:Yesno-yes" title="Template:Yesno-yes">Template:Yesno-yes</a> (<a href="/w/index.php?title=Template:Yesno-yes&action=edit" title="Template:Yesno-yes">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Arguments" title="Module:Arguments">Module:Arguments</a> (<a href="/w/index.php?title=Module:Arguments&action=edit" title="Module:Arguments">view source</a>) (protected)</li><li><a href="/wiki/Module:Authority_control" title="Module:Authority control">Module:Authority control</a> (<a href="/w/index.php?title=Module:Authority_control&action=edit" title="Module:Authority control">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Authority_control/config" title="Module:Authority control/config">Module:Authority control/config</a> (<a href="/w/index.php?title=Module:Authority_control/config&action=edit" title="Module:Authority control/config">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Catalog_lookup_link" title="Module:Catalog lookup link">Module:Catalog lookup link</a> (<a href="/w/index.php?title=Module:Catalog_lookup_link&action=edit" title="Module:Catalog lookup link">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Category_handler" title="Module:Category handler">Module:Category handler</a> (<a href="/w/index.php?title=Module:Category_handler&action=edit" title="Module:Category handler">view source</a>) (protected)</li><li><a href="/wiki/Module:Category_handler/blacklist" title="Module:Category handler/blacklist">Module:Category handler/blacklist</a> (<a href="/w/index.php?title=Module:Category_handler/blacklist&action=edit" title="Module:Category handler/blacklist">view source</a>) (protected)</li><li><a href="/wiki/Module:Category_handler/config" title="Module:Category handler/config">Module:Category handler/config</a> (<a href="/w/index.php?title=Module:Category_handler/config&action=edit" title="Module:Category handler/config">view source</a>) (protected)</li><li><a href="/wiki/Module:Category_handler/data" title="Module:Category handler/data">Module:Category handler/data</a> (<a href="/w/index.php?title=Module:Category_handler/data&action=edit" title="Module:Category handler/data">view source</a>) (protected)</li><li><a href="/wiki/Module:Category_handler/shared" title="Module:Category handler/shared">Module:Category handler/shared</a> (<a href="/w/index.php?title=Module:Category_handler/shared&action=edit" title="Module:Category handler/shared">view source</a>) (protected)</li><li><a href="/wiki/Module:Check_for_unknown_parameters" title="Module:Check for unknown parameters">Module:Check for unknown parameters</a> (<a href="/w/index.php?title=Module:Check_for_unknown_parameters&action=edit" title="Module:Check for unknown parameters">view source</a>) (protected)</li><li><a href="/wiki/Module:Check_isxn" title="Module:Check isxn">Module:Check isxn</a> (<a href="/w/index.php?title=Module:Check_isxn&action=edit" title="Module:Check isxn">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Citation/CS1" title="Module:Citation/CS1">Module:Citation/CS1</a> (<a href="/w/index.php?title=Module:Citation/CS1&action=edit" title="Module:Citation/CS1">view source</a>) (protected)</li><li><a href="/wiki/Module:Citation/CS1/COinS" title="Module:Citation/CS1/COinS">Module:Citation/CS1/COinS</a> (<a href="/w/index.php?title=Module:Citation/CS1/COinS&action=edit" title="Module:Citation/CS1/COinS">view source</a>) (protected)</li><li><a href="/wiki/Module:Citation/CS1/Configuration" title="Module:Citation/CS1/Configuration">Module:Citation/CS1/Configuration</a> (<a href="/w/index.php?title=Module:Citation/CS1/Configuration&action=edit" title="Module:Citation/CS1/Configuration">view source</a>) (protected)</li><li><a href="/wiki/Module:Citation/CS1/Date_validation" title="Module:Citation/CS1/Date validation">Module:Citation/CS1/Date validation</a> (<a href="/w/index.php?title=Module:Citation/CS1/Date_validation&action=edit" title="Module:Citation/CS1/Date validation">view source</a>) (protected)</li><li><a href="/wiki/Module:Citation/CS1/Identifiers" title="Module:Citation/CS1/Identifiers">Module:Citation/CS1/Identifiers</a> (<a href="/w/index.php?title=Module:Citation/CS1/Identifiers&action=edit" title="Module:Citation/CS1/Identifiers">view source</a>) (protected)</li><li><a href="/wiki/Module:Citation/CS1/Utilities" title="Module:Citation/CS1/Utilities">Module:Citation/CS1/Utilities</a> (<a href="/w/index.php?title=Module:Citation/CS1/Utilities&action=edit" title="Module:Citation/CS1/Utilities">view source</a>) (protected)</li><li><a href="/wiki/Module:Citation/CS1/Whitelist" title="Module:Citation/CS1/Whitelist">Module:Citation/CS1/Whitelist</a> (<a href="/w/index.php?title=Module:Citation/CS1/Whitelist&action=edit" title="Module:Citation/CS1/Whitelist">view source</a>) (protected)</li><li><a href="/wiki/Module:Citation/CS1/styles.css" title="Module:Citation/CS1/styles.css">Module:Citation/CS1/styles.css</a> (<a href="/w/index.php?title=Module:Citation/CS1/styles.css&action=edit" title="Module:Citation/CS1/styles.css">view source</a>) (protected)</li><li><a href="/wiki/Module:Delink" title="Module:Delink">Module:Delink</a> (<a href="/w/index.php?title=Module:Delink&action=edit" title="Module:Delink">view source</a>) (protected)</li><li><a href="/wiki/Module:Disambiguation/templates" title="Module:Disambiguation/templates">Module:Disambiguation/templates</a> (<a href="/w/index.php?title=Module:Disambiguation/templates&action=edit" title="Module:Disambiguation/templates">view source</a>) (protected)</li><li><a href="/wiki/Module:EditAtWikidata" title="Module:EditAtWikidata">Module:EditAtWikidata</a> (<a href="/w/index.php?title=Module:EditAtWikidata&action=edit" title="Module:EditAtWikidata">view source</a>) (protected)</li><li><a href="/wiki/Module:Find_sources" title="Module:Find sources">Module:Find sources</a> (<a href="/w/index.php?title=Module:Find_sources&action=edit" title="Module:Find sources">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Find_sources/config" title="Module:Find sources/config">Module:Find sources/config</a> (<a href="/w/index.php?title=Module:Find_sources/config&action=edit" title="Module:Find sources/config">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Find_sources/links" title="Module:Find sources/links">Module:Find sources/links</a> (<a href="/w/index.php?title=Module:Find_sources/links&action=edit" title="Module:Find sources/links">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Find_sources/templates/Find_sources_mainspace" title="Module:Find sources/templates/Find sources mainspace">Module:Find sources/templates/Find sources mainspace</a> (<a href="/w/index.php?title=Module:Find_sources/templates/Find_sources_mainspace&action=edit" title="Module:Find sources/templates/Find sources mainspace">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Footnotes" title="Module:Footnotes">Module:Footnotes</a> (<a href="/w/index.php?title=Module:Footnotes&action=edit" title="Module:Footnotes">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Footnotes/anchor_id_list" title="Module:Footnotes/anchor id list">Module:Footnotes/anchor id list</a> (<a href="/w/index.php?title=Module:Footnotes/anchor_id_list&action=edit" title="Module:Footnotes/anchor id list">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Footnotes/anchor_id_list/data" title="Module:Footnotes/anchor id list/data">Module:Footnotes/anchor id list/data</a> (<a href="/w/index.php?title=Module:Footnotes/anchor_id_list/data&action=edit" title="Module:Footnotes/anchor id list/data">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Footnotes/whitelist" title="Module:Footnotes/whitelist">Module:Footnotes/whitelist</a> (<a href="/w/index.php?title=Module:Footnotes/whitelist&action=edit" title="Module:Footnotes/whitelist">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Format_link" title="Module:Format link">Module:Format link</a> (<a href="/w/index.php?title=Module:Format_link&action=edit" title="Module:Format link">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Hatnote" title="Module:Hatnote">Module:Hatnote</a> (<a href="/w/index.php?title=Module:Hatnote&action=edit" title="Module:Hatnote">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Hatnote/styles.css" title="Module:Hatnote/styles.css">Module:Hatnote/styles.css</a> (<a href="/w/index.php?title=Module:Hatnote/styles.css&action=edit" title="Module:Hatnote/styles.css">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Hatnote_list" title="Module:Hatnote list">Module:Hatnote list</a> (<a href="/w/index.php?title=Module:Hatnote_list&action=edit" title="Module:Hatnote list">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Icon" title="Module:Icon">Module:Icon</a> (<a href="/w/index.php?title=Module:Icon&action=edit" title="Module:Icon">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Icon/data" title="Module:Icon/data">Module:Icon/data</a> (<a href="/w/index.php?title=Module:Icon/data&action=edit" title="Module:Icon/data">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Labelled_list_hatnote" title="Module:Labelled list hatnote">Module:Labelled list hatnote</a> (<a href="/w/index.php?title=Module:Labelled_list_hatnote&action=edit" title="Module:Labelled list hatnote">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Message_box" title="Module:Message box">Module:Message box</a> (<a href="/w/index.php?title=Module:Message_box&action=edit" title="Module:Message box">view source</a>) (protected)</li><li><a href="/wiki/Module:Message_box/ambox.css" title="Module:Message box/ambox.css">Module:Message box/ambox.css</a> (<a href="/w/index.php?title=Module:Message_box/ambox.css&action=edit" title="Module:Message box/ambox.css">view source</a>) (protected)</li><li><a href="/wiki/Module:Message_box/configuration" title="Module:Message box/configuration">Module:Message box/configuration</a> (<a href="/w/index.php?title=Module:Message_box/configuration&action=edit" title="Module:Message box/configuration">view source</a>) (protected)</li><li><a href="/wiki/Module:Namespace_detect/config" title="Module:Namespace detect/config">Module:Namespace detect/config</a> (<a href="/w/index.php?title=Module:Namespace_detect/config&action=edit" title="Module:Namespace detect/config">view source</a>) (protected)</li><li><a href="/wiki/Module:Namespace_detect/data" title="Module:Namespace detect/data">Module:Namespace detect/data</a> (<a href="/w/index.php?title=Module:Namespace_detect/data&action=edit" title="Module:Namespace detect/data">view source</a>) (protected)</li><li><a href="/wiki/Module:Navbar" title="Module:Navbar">Module:Navbar</a> (<a href="/w/index.php?title=Module:Navbar&action=edit" title="Module:Navbar">view source</a>) (protected)</li><li><a href="/wiki/Module:Navbar/configuration" title="Module:Navbar/configuration">Module:Navbar/configuration</a> (<a href="/w/index.php?title=Module:Navbar/configuration&action=edit" title="Module:Navbar/configuration">view source</a>) (protected)</li><li><a href="/wiki/Module:Navbar/styles.css" title="Module:Navbar/styles.css">Module:Navbar/styles.css</a> (<a href="/w/index.php?title=Module:Navbar/styles.css&action=edit" title="Module:Navbar/styles.css">view source</a>) (protected)</li><li><a href="/wiki/Module:Navbox" title="Module:Navbox">Module:Navbox</a> (<a href="/w/index.php?title=Module:Navbox&action=edit" title="Module:Navbox">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Navbox/configuration" title="Module:Navbox/configuration">Module:Navbox/configuration</a> (<a href="/w/index.php?title=Module:Navbox/configuration&action=edit" title="Module:Navbox/configuration">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Navbox/styles.css" title="Module:Navbox/styles.css">Module:Navbox/styles.css</a> (<a href="/w/index.php?title=Module:Navbox/styles.css&action=edit" title="Module:Navbox/styles.css">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Pagetype" title="Module:Pagetype">Module:Pagetype</a> (<a href="/w/index.php?title=Module:Pagetype&action=edit" title="Module:Pagetype">view source</a>) (protected)</li><li><a href="/wiki/Module:Pagetype/config" title="Module:Pagetype/config">Module:Pagetype/config</a> (<a href="/w/index.php?title=Module:Pagetype/config&action=edit" title="Module:Pagetype/config">view source</a>) (protected)</li><li><a href="/wiki/Module:Pagetype/disambiguation" class="mw-redirect" title="Module:Pagetype/disambiguation">Module:Pagetype/disambiguation</a> (<a href="/w/index.php?title=Module:Pagetype/disambiguation&action=edit" class="mw-redirect" title="Module:Pagetype/disambiguation">view source</a>) (protected)</li><li><a href="/wiki/Module:Pagetype/rfd" title="Module:Pagetype/rfd">Module:Pagetype/rfd</a> (<a href="/w/index.php?title=Module:Pagetype/rfd&action=edit" title="Module:Pagetype/rfd">view source</a>) (protected)</li><li><a href="/wiki/Module:Pagetype/setindex" title="Module:Pagetype/setindex">Module:Pagetype/setindex</a> (<a href="/w/index.php?title=Module:Pagetype/setindex&action=edit" title="Module:Pagetype/setindex">view source</a>) (protected)</li><li><a href="/wiki/Module:Pagetype/softredirect" title="Module:Pagetype/softredirect">Module:Pagetype/softredirect</a> (<a href="/w/index.php?title=Module:Pagetype/softredirect&action=edit" title="Module:Pagetype/softredirect">view source</a>) (protected)</li><li><a href="/wiki/Module:SDcat" title="Module:SDcat">Module:SDcat</a> (<a href="/w/index.php?title=Module:SDcat&action=edit" title="Module:SDcat">view source</a>) (protected)</li><li><a href="/wiki/Module:Side_box" title="Module:Side box">Module:Side box</a> (<a href="/w/index.php?title=Module:Side_box&action=edit" title="Module:Side box">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:Side_box/styles.css" title="Module:Side box/styles.css">Module:Side box/styles.css</a> (<a href="/w/index.php?title=Module:Side_box/styles.css&action=edit" title="Module:Side box/styles.css">view source</a>) (template editor protected)</li><li><a href="/wiki/Module:String" title="Module:String">Module:String</a> (<a href="/w/index.php?title=Module:String&action=edit" title="Module:String">view source</a>) (protected)</li><li><a href="/wiki/Module:TableTools" title="Module:TableTools">Module:TableTools</a> (<a href="/w/index.php?title=Module:TableTools&action=edit" title="Module:TableTools">view source</a>) (protected)</li><li><a href="/wiki/Module:Unsubst" title="Module:Unsubst">Module:Unsubst</a> (<a href="/w/index.php?title=Module:Unsubst&action=edit" title="Module:Unsubst">view source</a>) (protected)</li><li><a href="/wiki/Module:Wikitext_Parsing" title="Module:Wikitext Parsing">Module:Wikitext Parsing</a> (<a href="/w/index.php?title=Module:Wikitext_Parsing&action=edit" title="Module:Wikitext Parsing">view source</a>) (protected)</li><li><a href="/wiki/Module:Yesno" title="Module:Yesno">Module:Yesno</a> (<a href="/w/index.php?title=Module:Yesno&action=edit" title="Module:Yesno">view source</a>) (protected)</li></ul></div><p id="mw-returnto">Return to <a href="/wiki/Relational_database" title="Relational database">Relational database</a>.</p> <noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1&useformat=desktop" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/wiki/Relational_database">https://en.wikipedia.org/wiki/Relational_database</a>"</div></div> <div id="catlinks" class="catlinks catlinks-allhidden" data-mw="interface"></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> </ul> <ul id="footer-places"> <li id="footer-places-privacy"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy">Privacy policy</a></li> <li id="footer-places-about"><a href="/wiki/Wikipedia:About">About Wikipedia</a></li> <li id="footer-places-disclaimers"><a href="/wiki/Wikipedia:General_disclaimer">Disclaimers</a></li> <li id="footer-places-contact"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us">Contact Wikipedia</a></li> <li id="footer-places-wm-codeofconduct"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Universal_Code_of_Conduct">Code of Conduct</a></li> <li id="footer-places-developers"><a href="https://developer.wikimedia.org">Developers</a></li> <li id="footer-places-statslink"><a href="https://stats.wikimedia.org/#/en.wikipedia.org">Statistics</a></li> <li id="footer-places-cookiestatement"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Cookie_statement">Cookie statement</a></li> <li id="footer-places-mobileview"><a href="//en.m.wikipedia.org/w/index.php?title=Relational_database&action=edit&mobileaction=toggle_view_mobile" class="noprint stopMobileRedirectToggle">Mobile view</a></li> </ul> <ul id="footer-icons" class="noprint"> <li id="footer-copyrightico"><a href="https://wikimediafoundation.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><img src="/static/images/footer/wikimedia-button.svg" width="84" height="29" alt="Wikimedia Foundation" loading="lazy"></a></li> <li id="footer-poweredbyico"><a href="https://www.mediawiki.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><img src="/w/resources/assets/poweredby_mediawiki.svg" alt="Powered by MediaWiki" width="88" height="31" loading="lazy"></a></li> </ul> </footer> </div> </div> </div> <div class="vector-settings" id="p-dock-bottom"> <ul></ul> </div><script>(RLQ=window.RLQ||[]).push(function(){mw.config.set({"wgHostname":"mw-web.codfw.main-5c59558b9d-6n87w","wgBackendResponseTime":333,"wgPageParseReport":{"limitreport":{"cputime":"0.049","walltime":"0.068","ppvisitednodes":{"value":418,"limit":1000000},"postexpandincludesize":{"value":17740,"limit":2097152},"templateargumentsize":{"value":6556,"limit":2097152},"expansiondepth":{"value":9,"limit":100},"expensivefunctioncount":{"value":0,"limit":500},"unstrip-depth":{"value":0,"limit":20},"unstrip-size":{"value":469,"limit":5000000},"entityaccesscount":{"value":0,"limit":400},"timingprofile":["100.00% 46.396 1 -total"," 99.87% 46.335 2 Template:Blocked_text"," 42.01% 19.491 2 Template:Replace"," 38.77% 17.988 1 Template:Colocationwebhost"," 35.27% 16.365 1 Template:Hidden"," 15.02% 6.969 1 Template:Tlx"," 14.44% 6.701 1 Template:Hidden_begin"," 2.37% 1.098 1 MediaWiki:Wikimedia-globalblocking-blockedtext-mistake"," 2.26% 1.047 1 Template:Hidden_end"," 2.19% 1.016 1 MediaWiki:Wikimedia-globalblocking-blockedtext-mistake-email-steward"]},"scribunto":{"limitreport-timeusage":{"value":"0.009","limit":"10.000"},"limitreport-memusage":{"value":1043326,"limit":52428800}},"cachereport":{"origin":"mw-web.codfw.main-5c59558b9d-6n87w","timestamp":"20241130232254","ttl":2592000,"transientcontent":false}}});});</script> </body> </html>