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vector-toc-pinnable-header vector-pinnable-header-pinned" data-feature-name="toc-pinned" data-pinnable-element-id="vector-toc" > <h2 class="vector-pinnable-header-label">Indice</h2> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-toc.pin">sposta nella barra laterale</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-toc.unpin">nascondi</button> </div> <ul class="vector-toc-contents" id="mw-panel-toc-list"> <li id="toc-mw-content-text" class="vector-toc-list-item vector-toc-level-1"> <a href="#" class="vector-toc-link"> <div class="vector-toc-text">Inizio</div> </a> </li> <li id="toc-Tabelle_di_esempio" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Tabelle_di_esempio"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>Tabelle di esempio</span> </div> </a> <ul id="toc-Tabelle_di_esempio-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Inner_join" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Inner_join"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Inner join</span> </div> </a> <button aria-controls="toc-Inner_join-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Attiva/disattiva la sottosezione Inner join</span> </button> <ul id="toc-Inner_join-sublist" class="vector-toc-list"> <li id="toc-Equi-join" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Equi-join"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>Equi-join</span> </div> </a> <ul id="toc-Equi-join-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Natural_join" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Natural_join"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.2</span> <span>Natural join</span> </div> </a> <ul id="toc-Natural_join-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Cross_join" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Cross_join"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.3</span> <span>Cross join</span> </div> </a> <ul id="toc-Cross_join-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Outer_join" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Outer_join"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Outer join</span> </div> </a> <button aria-controls="toc-Outer_join-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Attiva/disattiva la sottosezione Outer join</span> </button> <ul id="toc-Outer_join-sublist" class="vector-toc-list"> <li id="toc-Nota_sulle_clausole_WHERE_e_ON" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Nota_sulle_clausole_WHERE_e_ON"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Nota sulle clausole WHERE e ON</span> </div> </a> <ul id="toc-Nota_sulle_clausole_WHERE_e_ON-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Left_outer_join" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Left_outer_join"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Left outer join</span> </div> </a> <ul id="toc-Left_outer_join-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Right_outer_join" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Right_outer_join"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.3</span> <span>Right outer join</span> </div> </a> <ul id="toc-Right_outer_join-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Full_outer_join" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Full_outer_join"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.4</span> <span>Full outer join</span> </div> </a> <ul id="toc-Full_outer_join-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Self-join" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Self-join"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Self-join</span> </div> </a> <ul id="toc-Self-join-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Voci_correlate" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Voci_correlate"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Voci correlate</span> </div> </a> <ul id="toc-Voci_correlate-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Altri_progetti" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Altri_progetti"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Altri progetti</span> </div> </a> <ul id="toc-Altri_progetti-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Collegamenti_esterni" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Collegamenti_esterni"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>Collegamenti esterni</span> </div> </a> <ul id="toc-Collegamenti_esterni-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Indice" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Indice" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Mostra/Nascondi l'indice" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-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-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Mostra/Nascondi l'indice</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Join (SQL)</span></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="Vai a una voce in un'altra lingua. Disponibile in 21 lingue" > <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-21" 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">21 lingue</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/Daxili_birl%C9%99%C5%9Fdirm%C9%99" title="Daxili birləşdirmə - azerbaigiano" lang="az" hreflang="az" data-title="Daxili birləşdirmə" data-language-autonym="Azərbaycanca" data-language-local-name="azerbaigiano" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - catalano" lang="ca" hreflang="ca" data-title="Join (SQL)" data-language-autonym="Català" data-language-local-name="catalano" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/JOIN" title="JOIN - ceco" lang="cs" hreflang="cs" data-title="JOIN" data-language-autonym="Čeština" data-language-local-name="ceco" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - danese" lang="da" hreflang="da" data-title="Join (SQL)" data-language-autonym="Dansk" data-language-local-name="danese" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - tedesco" lang="de" hreflang="de" data-title="Join (SQL)" data-language-autonym="Deutsch" data-language-local-name="tedesco" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-en mw-list-item"><a href="https://en.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - inglese" lang="en" hreflang="en" data-title="Join (SQL)" data-language-autonym="English" data-language-local-name="inglese" class="interlanguage-link-target"><span>English</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Sentencia_JOIN_en_SQL" title="Sentencia JOIN en SQL - spagnolo" lang="es" hreflang="es" data-title="Sentencia JOIN en SQL" data-language-autonym="Español" data-language-local-name="spagnolo" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Jointure_(informatique)" title="Jointure (informatique) - francese" lang="fr" hreflang="fr" data-title="Jointure (informatique)" data-language-autonym="Français" data-language-local-name="francese" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - ebraico" lang="he" hreflang="he" data-title="Join (SQL)" data-language-autonym="עברית" data-language-local-name="ebraico" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - armeno" lang="hy" hreflang="hy" data-title="Join (SQL)" data-language-autonym="Հայերեն" data-language-local-name="armeno" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - coreano" lang="ko" hreflang="ko" data-title="Join (SQL)" data-language-autonym="한국어" data-language-local-name="coreano" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - olandese" lang="nl" hreflang="nl" data-title="Join (SQL)" data-language-autonym="Nederlands" data-language-local-name="olandese" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - norvegese bokmål" lang="nb" hreflang="nb" data-title="Join (SQL)" data-language-autonym="Norsk bokmål" data-language-local-name="norvegese bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - polacco" lang="pl" hreflang="pl" data-title="Join (SQL)" data-language-autonym="Polski" data-language-local-name="polacco" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - portoghese" lang="pt" hreflang="pt" data-title="Join (SQL)" data-language-autonym="Português" data-language-local-name="portoghese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - russo" lang="ru" hreflang="ru" data-title="Join (SQL)" data-language-autonym="Русский" data-language-local-name="russo" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - Simple English" lang="en-simple" hreflang="en-simple" data-title="Join (SQL)" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - serbo" lang="sr" hreflang="sr" data-title="Join (SQL)" data-language-autonym="Српски / srpski" data-language-local-name="serbo" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - ucraino" lang="uk" hreflang="uk" data-title="Join (SQL)" data-language-autonym="Українська" data-language-local-name="ucraino" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Join_(SQL)" title="Join (SQL) - vietnamita" lang="vi" hreflang="vi" data-title="Join (SQL)" data-language-autonym="Tiếng Việt" data-language-local-name="vietnamita" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E8%BF%9E%E6%8E%A5" title="连接 - cinese" lang="zh" hreflang="zh" data-title="连接" data-language-autonym="中文" data-language-local-name="cinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q2003535#sitelinks-wikipedia" title="Modifica collegamenti interlinguistici" class="wbc-editpage">Modifica collegamenti</a></span></div> </div> </div> </div> </header> <div class="vector-page-toolbar"> <div class="vector-page-toolbar-container"> <div id="left-navigation"> <nav aria-label="Namespace"> <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/Join_(SQL)" title="Vedi la voce [c]" accesskey="c"><span>Voce</span></a></li><li id="ca-talk" class="vector-tab-noicon mw-list-item"><a href="/wiki/Discussione:Join_(SQL)" rel="discussion" title="Vedi le discussioni relative a questa pagina [t]" accesskey="t"><span>Discussione</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="Cambia versione linguistica" > <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">italiano</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="Visite"> <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="selected vector-tab-noicon mw-list-item"><a href="/wiki/Join_(SQL)"><span>Leggi</span></a></li><li id="ca-ve-edit" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Join_(SQL)&veaction=edit" title="Modifica questa pagina [v]" accesskey="v"><span>Modifica</span></a></li><li id="ca-edit" class="collapsible vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Join_(SQL)&action=edit" title="Modifica il wikitesto di questa pagina [e]" accesskey="e"><span>Modifica wikitesto</span></a></li><li id="ca-history" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Join_(SQL)&action=history" title="Versioni precedenti di questa pagina [h]" accesskey="h"><span>Cronologia</span></a></li> </ul> </div> </div> </nav> <nav class="vector-page-tools-landmark" aria-label="Strumenti pagine"> <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="Strumenti" > <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">Strumenti</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">Strumenti</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-page-tools.pin">sposta nella barra laterale</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-page-tools.unpin">nascondi</button> </div> <div id="p-cactions" class="vector-menu mw-portlet mw-portlet-cactions emptyPortlet vector-has-collapsible-items" title="Altre opzioni" > <div class="vector-menu-heading"> Azioni </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-more-view" class="selected vector-more-collapsible-item mw-list-item"><a href="/wiki/Join_(SQL)"><span>Leggi</span></a></li><li id="ca-more-ve-edit" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Join_(SQL)&veaction=edit" title="Modifica questa pagina [v]" accesskey="v"><span>Modifica</span></a></li><li id="ca-more-edit" class="collapsible vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Join_(SQL)&action=edit" title="Modifica il wikitesto di questa pagina [e]" accesskey="e"><span>Modifica wikitesto</span></a></li><li id="ca-more-history" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Join_(SQL)&action=history"><span>Cronologia</span></a></li> </ul> </div> </div> <div id="p-tb" class="vector-menu mw-portlet mw-portlet-tb" > <div class="vector-menu-heading"> Generale </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-whatlinkshere" class="mw-list-item"><a href="/wiki/Speciale:PuntanoQui/Join_(SQL)" title="Elenco di tutte le pagine che sono collegate a questa [j]" accesskey="j"><span>Puntano qui</span></a></li><li id="t-recentchangeslinked" class="mw-list-item"><a href="/wiki/Speciale:ModificheCorrelate/Join_(SQL)" rel="nofollow" title="Elenco delle ultime modifiche alle pagine collegate a questa [k]" accesskey="k"><span>Modifiche correlate</span></a></li><li id="t-permalink" class="mw-list-item"><a href="/w/index.php?title=Join_(SQL)&oldid=143542491" title="Collegamento permanente a questa versione di questa pagina"><span>Link permanente</span></a></li><li id="t-info" class="mw-list-item"><a href="/w/index.php?title=Join_(SQL)&action=info" title="Ulteriori informazioni su questa pagina"><span>Informazioni pagina</span></a></li><li id="t-cite" class="mw-list-item"><a href="/w/index.php?title=Speciale:Cita&page=Join_%28SQL%29&id=143542491&wpFormIdentifier=titleform" title="Informazioni su come citare questa pagina"><span>Cita questa voce</span></a></li><li id="t-urlshortener" class="mw-list-item"><a href="/w/index.php?title=Speciale:UrlShortener&url=https%3A%2F%2Fit.wikipedia.org%2Fwiki%2FJoin_%28SQL%29"><span>Ottieni URL breve</span></a></li><li id="t-urlshortener-qrcode" class="mw-list-item"><a href="/w/index.php?title=Speciale:QrCode&url=https%3A%2F%2Fit.wikipedia.org%2Fwiki%2FJoin_%28SQL%29"><span>Scarica codice QR</span></a></li> </ul> </div> </div> <div id="p-coll-print_export" class="vector-menu mw-portlet mw-portlet-coll-print_export" > <div class="vector-menu-heading"> Stampa/esporta </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="coll-create_a_book" class="mw-list-item"><a href="/w/index.php?title=Speciale:Libro&bookcmd=book_creator&referer=Join+%28SQL%29"><span>Crea un libro</span></a></li><li id="coll-download-as-rl" class="mw-list-item"><a href="/w/index.php?title=Speciale:DownloadAsPdf&page=Join_%28SQL%29&action=show-download-screen"><span>Scarica come PDF</span></a></li><li id="t-print" class="mw-list-item"><a href="/w/index.php?title=Join_(SQL)&printable=yes" title="Versione stampabile di questa pagina [p]" accesskey="p"><span>Versione stampabile</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 altri progetti </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="wb-otherproject-link wb-otherproject-commons mw-list-item"><a href="https://commons.wikimedia.org/wiki/Category:SQL_Joins" hreflang="en"><span>Wikimedia Commons</span></a></li><li id="t-wikibase" class="wb-otherproject-link wb-otherproject-wikibase-dataitem mw-list-item"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q2003535" title="Collegamento all'elemento connesso dell'archivio dati [g]" accesskey="g"><span>Elemento Wikidata</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="Strumenti pagine"> <div id="vector-page-tools-pinned-container" class="vector-pinned-container"> </div> </nav> <nav class="vector-appearance-landmark" aria-label="Aspetto"> <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">Aspetto</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">sposta nella barra laterale</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">nascondi</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 id="siteSub" class="noprint">Da Wikipedia, l'enciclopedia libera.</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="it" dir="ltr"><style data-mw-deduplicate="TemplateStyles:r133964453">.mw-parser-output .avviso .mbox-text-div>div,.mw-parser-output .avviso .mbox-text-full-div>div{font-size:90%}.mw-parser-output .avviso .mbox-image{flex-basis:52px;flex-grow:0;flex-shrink:0}.mw-parser-output .avviso .mbox-text-full-div .hide-when-compact{display:block}</style><div style="" class="ambox metadata plainlinks avviso avviso-contenuto"> <div class="avviso-immagine mbox-image noprint"><span typeof="mw:File"><a href="/wiki/File:Question_book-4.svg" class="mw-file-description" title="Niente fonti!"><img alt="Niente fonti!" src="//upload.wikimedia.org/wikipedia/commons/thumb/6/64/Question_book-4.svg/45px-Question_book-4.svg.png" decoding="async" width="45" height="35" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/64/Question_book-4.svg/68px-Question_book-4.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/64/Question_book-4.svg/90px-Question_book-4.svg.png 2x" data-file-width="262" data-file-height="204" /></a></span></div> <div class="avviso-testo mbox-text"> <div class="mbox-text-div"><b>Questa voce o sezione  sull'argomento programmazione <a href="/wiki/Wikipedia:Uso_delle_fonti" title="Wikipedia:Uso delle fonti">non cita le fonti necessarie</a> o quelle presenti sono insufficienti</b>. <div class="hide-when-compact"> <div class="noprint"><hr />Puoi <a class="external text" href="https://it.wikipedia.org/w/index.php?title=Join_(SQL)&action=edit">migliorare questa voce</a> aggiungendo citazioni da <a href="/wiki/Wikipedia:Fonti_attendibili" title="Wikipedia:Fonti attendibili">fonti attendibili</a> secondo le <a href="/wiki/Wikipedia:Uso_delle_fonti" title="Wikipedia:Uso delle fonti">linee guida sull'uso delle fonti</a>. </div> </div> </div> </div> </div> <p>La <b>JOIN</b> è una clausola del linguaggio <a href="/wiki/SQL" class="mw-redirect" title="SQL">SQL</a> che serve a combinare le <a href="/wiki/Tuple" class="mw-redirect" title="Tuple">tuple</a> di due o più <a href="/wiki/Modello_relazionale" title="Modello relazionale">relazioni</a> di una <a href="/wiki/Base_di_dati" title="Base di dati">base di dati</a>. Lo standard <a href="/wiki/ANSI" class="mw-redirect" title="ANSI">ANSI</a> definisce alcune specifiche per il linguaggio SQL sul tipo di JOIN da effettuare: <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">INNER</span><span class="w"> </span><span class="k">JOIN</span></code>, <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">FULL</span><span class="w"> </span><span class="k">JOIN</span></code>, <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">LEFT</span><span class="w"> </span><span class="k">JOIN</span></code> e <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">RIGHT</span><span class="w"> </span><span class="k">JOIN</span></code>, alle quali diversi <a href="/wiki/DBMS" class="mw-redirect" title="DBMS">DBMS</a> aggiungono <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">CROSS</span><span class="w"> </span><span class="k">JOIN</span></code>. In alcuni casi è possibile che una tabella possa essere combinata con se stessa, in questo caso si parlerà di <i>self-join</i>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Tabelle_di_esempio">Tabelle di esempio</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Join_(SQL)&veaction=edit&section=1" title="Modifica la sezione Tabelle di esempio" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Join_(SQL)&action=edit&section=1" title="Edit section's source code: Tabelle di esempio"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Tutti gli esempi che verranno riportati di seguito faranno uso delle seguenti due tabelle: </p> <table class="wikitable" style="text-align:center; float:left; margin-right:5px"> <caption>Tabella Impiegati </caption> <tbody><tr> <th>Cognome</th> <th>ID_dipartimento </th></tr> <tr> <td>Rossi</td> <td>31 </td></tr> <tr> <td>Bianchi</td> <td>33 </td></tr> <tr> <td>Mancini</td> <td>33 </td></tr> <tr> <td>Santoro</td> <td>34 </td></tr> <tr> <td>Monti</td> <td>34 </td></tr> <tr> <td>Grassi</td> <td><code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code> </td></tr></tbody></table> <table class="wikitable" style="text-align:center; float:left; margin-left:5px"> <caption>Tabella Dipartimenti </caption> <tbody><tr> <th>ID_dipartimento</th> <th>Nome_dipartimento </th></tr> <tr> <td>31</td> <td>Vendite </td></tr> <tr> <td>33</td> <td>Tecnico </td></tr> <tr> <td>34</td> <td>Risorse umane </td></tr> <tr> <td>35</td> <td>Promozione </td></tr></tbody></table> <div style="clear:both;"></div> <p><code>Dipartimenti.ID_dipartimento</code> è la <a href="/wiki/Chiave_primaria" title="Chiave primaria">chiave primaria</a> che ha una <a href="/wiki/Cardinalit%C3%A0" title="Cardinalità">cardinalità</a> 0:n nei confronti del campo <code>Impiegati.ID_dipartimento</code>. </p><p>Nota: Il dipartimento <code>Promozione</code> della tabella <code>Dipartimenti</code> non ha alcuna corrispondenza nella tabella <code>Impiegati</code>. Mentre l'impiegato <code>Grassi</code> non è stato assegnato ad alcun dipartimento (<a href="/wiki/NULL" title="NULL">NULL</a>). </p> <div class="mw-heading mw-heading2"><h2 id="Inner_join">Inner join</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Join_(SQL)&veaction=edit&section=2" title="Modifica la sezione Inner join" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Join_(SQL)&action=edit&section=2" title="Edit section's source code: Inner join"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:SQL_Join_-_07_A_Inner_Join_B.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/18/SQL_Join_-_07_A_Inner_Join_B.svg/220px-SQL_Join_-_07_A_Inner_Join_B.svg.png" decoding="async" width="220" height="149" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/18/SQL_Join_-_07_A_Inner_Join_B.svg/330px-SQL_Join_-_07_A_Inner_Join_B.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/18/SQL_Join_-_07_A_Inner_Join_B.svg/440px-SQL_Join_-_07_A_Inner_Join_B.svg.png 2x" data-file-width="234" data-file-height="158" /></a><figcaption><a href="/wiki/Diagramma_di_Venn" title="Diagramma di Venn">Diagramma di Venn</a> che rappresenta la <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">INNER</span><span class="w"> </span><span class="k">JOIN</span></code> di due tabelle</figcaption></figure> <p>Una <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">INNER</span><span class="w"> </span><span class="k">JOIN</span></code> crea una nuova tabella combinando i valori delle due tabelle di partenza (<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span> e <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span>) basandosi su una certa regola di confronto. La query compara ogni riga della tabella <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span> con ciascuna riga della tabella <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span> cercando di soddisfare la regola di confronto definita. Quando la regola di join viene soddisfatta, i valori di tutte le colonne delle tabelle <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span> e <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span> vengono combinate in un'unica riga nella costruzione della tabella risultante. La <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">INNER</span><span class="w"> </span><span class="k">JOIN</span></code> è la forma di join usata più di frequente nelle applicazioni e rappresenta la modalità predefinita. </p><p>Per esempio, la seguente query unirà le due tabelle <code>Impiegati</code> e <code>Dipartimenti</code> usando la chiave primaria <code>ID_dipartimento</code> che è la colonna presente in entrambe le tabelle. Quando <code>ID_dipartimento</code> corrisponde in entrambe le tabelle (ovvero la regola è soddisfatta), la query combinerà le colonne <code>Cognome</code>, <code>ID_dipartimento</code> e <code>Nome_dipartimento</code> in un'unica riga per la tabella risultante. </p><p>Esempio di <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">INNER</span><span class="w"> </span><span class="k">JOIN</span></code> in forma esplicita: </p> <div class="mw-highlight mw-highlight-lang-sql mw-content-ltr mw-highlight-lines" dir="ltr"><pre><span></span><span class="linenos" data-line="1"></span><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span> <span class="linenos" data-line="2"></span><span class="k">FROM</span><span class="w"> </span><span class="n">Impiegati</span><span class="w"> </span> <span class="linenos" data-line="3"></span><span class="w"> </span><span class="k">INNER</span><span class="w"> </span><span class="k">JOIN</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="w"> </span> <span class="linenos" data-line="4"></span><span class="w"> </span><span class="k">ON</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">.</span><span class="n">ID_dipartimento</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="p">.</span><span class="n">ID_dipartimento</span> </pre></div> <p>che equivale a: </p> <div class="mw-highlight mw-highlight-lang-sql mw-content-ltr mw-highlight-lines" dir="ltr"><pre><span></span><span class="linenos" data-line="1"></span><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span><span class="w"> </span> <span class="linenos" data-line="2"></span><span class="k">FROM</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">,</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="w"> </span> <span class="linenos" data-line="3"></span><span class="k">WHERE</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">.</span><span class="n">ID_dipartimento</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="p">.</span><span class="n">ID_dipartimento</span> </pre></div> <p>Risultato della query di <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">INNER</span><span class="w"> </span><span class="k">JOIN</span></code>: </p> <table class="wikitable" style="text-align:center"> <tbody><tr> <th>Impiegati.Cognome</th> <th>Impiegati.ID_dipartimento</th> <th>Dipartimenti.Nome_dipartimento</th> <th>Dipartimenti.ID_dipartimento </th></tr> <tr> <td>Santoro</td> <td>34</td> <td>Risorse umane</td> <td>34 </td></tr> <tr> <td>Bianchi</td> <td>33</td> <td>Tecnico</td> <td>33 </td></tr> <tr> <td>Monti</td> <td>34</td> <td>Risorse umane</td> <td>34 </td></tr> <tr> <td>Mancini</td> <td>33</td> <td>Tecnico</td> <td>33 </td></tr> <tr> <td>Rossi</td> <td>31</td> <td>Vendite</td> <td>31 </td></tr></tbody></table> <p>Nota: l'impiegato <code>Grassi</code> e il dipartimento <code>Promozione</code> non sono presenti in quanto l'impiegato <code>Grassi</code> ha un <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code> mentre <code>Promozione</code> non compare in nessun impiegato. A volte come risultato finale si desidera avere anche i record che non hanno corrispondenza: in tal caso è possibile usare la query di tipo <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code>. </p> <div class="mw-heading mw-heading3"><h3 id="Equi-join">Equi-join</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Join_(SQL)&veaction=edit&section=3" title="Modifica la sezione Equi-join" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Join_(SQL)&action=edit&section=3" title="Edit section's source code: Equi-join"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>La <i>equi-join</i>, noto come "l'unica operazione ammissibile", ha un particolare tipo di comparatore, detto <i>theta join</i>, che utilizza come metodo di verifica, solamente l'uguaglianza matematica come regola di confronto. Usare altri operatori di confronto (come ad esempio <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="o"><</span></code>) squalifica la <i>join</i> come <i>equi-join</i>. La query riportata di seguito utilizza una <i>equi-join</i>: </p> <div class="mw-highlight mw-highlight-lang-sql mw-content-ltr mw-highlight-lines" dir="ltr"><pre><span></span><span class="linenos" data-line="1"></span><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span> <span class="linenos" data-line="2"></span><span class="k">FROM</span><span class="w"> </span><span class="n">Impiegati</span><span class="w"> </span> <span class="linenos" data-line="3"></span><span class="w"> </span><span class="k">INNER</span><span class="w"> </span><span class="k">JOIN</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="w"> </span> <span class="linenos" data-line="4"></span><span class="w"> </span><span class="k">ON</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">.</span><span class="n">ID_dipartimento</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="p">.</span><span class="n">ID_dipartimento</span> </pre></div> <p>SQL fornisce una scorciatoia per definire le equi-joins, attraverso la <a href="/wiki/Parola_riservata" title="Parola riservata">parola riservata</a> <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">USING</span></code> </p> <div class="mw-highlight mw-highlight-lang-sql mw-content-ltr mw-highlight-lines" dir="ltr"><pre><span></span><span class="linenos" data-line="1"></span><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span> <span class="linenos" data-line="2"></span><span class="k">FROM</span><span class="w"> </span><span class="n">Impiegati</span><span class="w"> </span> <span class="linenos" data-line="3"></span><span class="w"> </span><span class="k">INNER</span><span class="w"> </span><span class="k">JOIN</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="w"> </span> <span class="linenos" data-line="4"></span><span class="w"> </span><span class="k">USING</span><span class="w"> </span><span class="p">(</span><span class="n">ID_dipartimento</span><span class="p">)</span> </pre></div> <p>La <i>keyword</i> <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">USING</span></code> è supportata da <a href="/w/index.php?title=Microsoft_SQL_Server_Management_Studio&action=edit&redlink=1" class="new" title="Microsoft SQL Server Management Studio (la pagina non esiste)">Microsoft SQL Server Management Studio</a>, <a href="/wiki/MySQL" title="MySQL">MySQL</a>, <a href="/wiki/Oracle_Database" title="Oracle Database">Oracle</a>, <a href="/wiki/PostgreSQL" title="PostgreSQL">PostgreSQL</a>, <a href="/wiki/SQLite" title="SQLite">SQLite</a>, e <a href="/wiki/IBM_DB2" title="IBM DB2">DB2/400</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Natural_join">Natural join</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Join_(SQL)&veaction=edit&section=4" title="Modifica la sezione Natural join" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Join_(SQL)&action=edit&section=4" title="Edit section's source code: Natural join"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Una <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NATURAL</span><span class="w"> </span><span class="k">JOIN</span></code> offre ulteriori specializzazioni di <i>equi-join</i>. Solitamente la <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">JOIN</span></code> confronta colonne di tabelle diverse che hanno lo stesso nome. La <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NATURAL</span><span class="w"> </span><span class="k">JOIN</span></code> fa proprio questo. </p><p>Nell'esempio che segue viene riportata la notazione <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NATURAL</span><span class="w"> </span><span class="k">JOIN</span></code> equivalente alla prima <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">INNER</span><span class="w"> </span><span class="k">JOIN</span></code> definita: </p> <div class="mw-highlight mw-highlight-lang-sql mw-content-ltr mw-highlight-lines" dir="ltr"><pre><span></span><span class="linenos" data-line="1"></span><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span> <span class="linenos" data-line="2"></span><span class="k">FROM</span><span class="w"> </span><span class="n">Impiegati</span><span class="w"> </span> <span class="linenos" data-line="3"></span><span class="w"> </span><span class="k">NATURAL</span><span class="w"> </span><span class="k">JOIN</span><span class="w"> </span><span class="n">Dipartimenti</span> </pre></div> <table class="wikitable" style="text-align:center"> <tbody><tr> <th>ID_dipartimento</th> <th>Impiegati.Cognome</th> <th>Dipartimenti.Nome_dipartimento </th></tr> <tr> <td>34</td> <td>Monti</td> <td>Risorse umane </td></tr> <tr> <td>33</td> <td>Bianchi</td> <td>Tecnico </td></tr> <tr> <td>34</td> <td>Santoro</td> <td>Risorse umane </td></tr> <tr> <td>33</td> <td>Mancini</td> <td>Tecnico </td></tr> <tr> <td>31</td> <td>Rossi</td> <td>Vendite </td></tr></tbody></table> <div class="mw-heading mw-heading3"><h3 id="Cross_join">Cross join</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Join_(SQL)&veaction=edit&section=5" title="Modifica la sezione Cross join" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Join_(SQL)&action=edit&section=5" title="Edit section's source code: Cross join"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:SQL_Join_-_08_A_Cross_Join_B.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/82/SQL_Join_-_08_A_Cross_Join_B.svg/220px-SQL_Join_-_08_A_Cross_Join_B.svg.png" decoding="async" width="220" height="145" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/82/SQL_Join_-_08_A_Cross_Join_B.svg/330px-SQL_Join_-_08_A_Cross_Join_B.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/82/SQL_Join_-_08_A_Cross_Join_B.svg/440px-SQL_Join_-_08_A_Cross_Join_B.svg.png 2x" data-file-width="301" data-file-height="198" /></a><figcaption>Immagine che rappresenta la <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">CROSS</span><span class="w"> </span><span class="k">JOIN</span></code> di due tabelle</figcaption></figure> <p>Una <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">CROSS</span><span class="w"> </span><span class="k">JOIN</span></code>, <i>cartesian join</i> o <i>product</i> fornisce le basi (le infrastrutture informatiche) attraverso cui tutti i tipi di <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">INNER</span><span class="w"> </span><span class="k">JOIN</span></code> operano. Il risultato di una <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">CROSS</span><span class="w"> </span><span class="k">JOIN</span></code> è il <a href="/wiki/Prodotto_cartesiano" title="Prodotto cartesiano">prodotto cartesiano</a> di tutte le righe delle tabelle che concorrono alla query di <i>join</i>. È come dire che stiamo facendo una <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">INNER</span><span class="w"> </span><span class="k">JOIN</span></code> senza impostare la regola di confronto o in cui la regola di confronto ritorna sempre vero. </p><p>Date le due tabelle di partenza <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span> e <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span>, la cross join si scrive <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span> × <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span>. </p><p>Esempio di <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">CROSS</span><span class="w"> </span><span class="k">JOIN</span></code> esplicito: </p> <div class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span> <span class="k">FROM</span><span class="w"> </span><span class="n">Impiegati</span><span class="w"> </span><span class="k">CROSS</span><span class="w"> </span><span class="k">JOIN</span><span class="w"> </span><span class="n">Dipartimenti</span> </pre></div> <p>Altro esempio implicito di <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">CROSS</span><span class="w"> </span><span class="k">JOIN</span></code>: </p> <div class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span> <span class="k">FROM</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">,</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="p">;</span> </pre></div> <table class="wikitable" style="text-align:center"> <tbody><tr> <th>Impiegati.Cognome</th> <th>Impiegati.ID_dipartimento</th> <th>Dipartimenti.Nome_dipartimento</th> <th>Dipartimenti.ID_dipartimento </th></tr> <tr> <td>Rossi</td> <td>31</td> <td>Vendite</td> <td>31 </td></tr> <tr> <td>Bianchi</td> <td>33</td> <td>Vendite</td> <td>31 </td></tr> <tr> <td>Mancini</td> <td>33</td> <td>Vendite</td> <td>31 </td></tr> <tr> <td>Monti</td> <td>34</td> <td>Vendite</td> <td>31 </td></tr> <tr> <td>Santoro</td> <td>34</td> <td>Vendite</td> <td>31 </td></tr> <tr> <td>Grassi</td> <td><code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code></td> <td>Vendite</td> <td>31 </td></tr> <tr> <td>Rossi</td> <td>31</td> <td>Tecnico</td> <td>33 </td></tr> <tr> <td>Bianchi</td> <td>33</td> <td>Tecnico</td> <td>33 </td></tr> <tr> <td>Mancini</td> <td>33</td> <td>Tecnico</td> <td>33 </td></tr> <tr> <td>Monti</td> <td>34</td> <td>Tecnico</td> <td>33 </td></tr> <tr> <td>Santoro</td> <td>34</td> <td>Tecnico</td> <td>33 </td></tr> <tr> <td>Grassi</td> <td><code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code></td> <td>Tecnico</td> <td>33 </td></tr> <tr> <td>Rossi</td> <td>31</td> <td>Risorse umane</td> <td>34 </td></tr> <tr> <td>Bianchi</td> <td>33</td> <td>Risorse umane</td> <td>34 </td></tr> <tr> <td>Mancini</td> <td>33</td> <td>Risorse umane</td> <td>34 </td></tr> <tr> <td>Monti</td> <td>34</td> <td>Risorse umane</td> <td>34 </td></tr> <tr> <td>Santoro</td> <td>34</td> <td>Risorse umane</td> <td>34 </td></tr> <tr> <td>Grassi</td> <td><code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code></td> <td>Risorse umane</td> <td>34 </td></tr> <tr> <td>Rossi</td> <td>31</td> <td>Promozione</td> <td>35 </td></tr> <tr> <td>Bianchi</td> <td>33</td> <td>Promozione</td> <td>35 </td></tr> <tr> <td>Mancini</td> <td>33</td> <td>Promozione</td> <td>35 </td></tr> <tr> <td>Monti</td> <td>34</td> <td>Promozione</td> <td>35 </td></tr> <tr> <td>Santoro</td> <td>34</td> <td>Promozione</td> <td>35 </td></tr> <tr> <td>Grassi</td> <td><code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code></td> <td>Promozione</td> <td>35 </td></tr></tbody></table> <div class="mw-heading mw-heading2"><h2 id="Outer_join">Outer join</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Join_(SQL)&veaction=edit&section=6" title="Modifica la sezione Outer join" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Join_(SQL)&action=edit&section=6" title="Edit section's source code: Outer join"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Una <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> non richiede che ci sia corrispondenza esatta tra le righe di due tabelle. La tabella risultante da una outer join trattiene tutti quei record che non hanno alcuna corrispondenza tra le tabelle. Le <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> si suddividono in <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">LEFT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code>, <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">RIGHT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code>, e <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">FULL</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code>, in base a quale sia la tabella di cui intendiamo trattenere i valori in caso di mancata corrispondenza della regola di confronto da (sinistra, destra, o entrambi). In questo caso <i>left</i> (sinistra) e <i>right</i> (destra) si riferiscono ai due lati della <i>keyword</i> <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">JOIN</span></code>. </p> <div class="mw-heading mw-heading3"><h3 id="Nota_sulle_clausole_WHERE_e_ON">Nota sulle clausole WHERE e ON</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Join_(SQL)&veaction=edit&section=7" title="Modifica la sezione Nota sulle clausole WHERE e ON" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Join_(SQL)&action=edit&section=7" title="Edit section's source code: Nota sulle clausole WHERE e ON"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Si sottolinea come esista un ordine di esecuzione tra le condizioni specificate nella <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">WHERE</span></code> e quelle presenti nella <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">ON</span></code>. </p><p>Specificatamente le clausole presenti nella <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">ON</span></code> sono valutate anteriormente all'esecuzione della <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">JOIN</span></code> mentre le clausole nella where sono valutate successivamente all'esecuzione della <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">JOIN</span></code>. </p> <div class="mw-heading mw-heading3"><h3 id="Left_outer_join">Left outer join</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Join_(SQL)&veaction=edit&section=8" title="Modifica la sezione Left outer join" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Join_(SQL)&action=edit&section=8" title="Edit section's source code: Left outer join"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:SQL_Join_-_01b_A_Left_Join_B.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/dc/SQL_Join_-_01b_A_Left_Join_B.svg/220px-SQL_Join_-_01b_A_Left_Join_B.svg.png" decoding="async" width="220" height="149" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/dc/SQL_Join_-_01b_A_Left_Join_B.svg/330px-SQL_Join_-_01b_A_Left_Join_B.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/dc/SQL_Join_-_01b_A_Left_Join_B.svg/440px-SQL_Join_-_01b_A_Left_Join_B.svg.png 2x" data-file-width="234" data-file-height="158" /></a><figcaption><a href="/wiki/Diagramma_di_Venn" title="Diagramma di Venn">Diagramma di Venn</a> che rappresenta la <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">LEFT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> di due tabelle</figcaption></figure> <p>Il risultato di una query <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">LEFT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> (o semplicemente <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">LEFT</span><span class="w"> </span><span class="k">JOIN</span></code>) per le tabelle <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span> e <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span> contiene sempre tutti i record della tabella di sinistra (<i>left</i>) <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span>, mentre vengono estratti dalla tabella di destra (<i>right</i>) <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span> solamente le righe che trovano corrispondenza nella regola di confronto della join. Questo significa che se la clausola <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">ON</span></code> trova zero righe in <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span>, la <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">JOIN</span></code> mostrerà una riga risultante con valore <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code> in tutte le colonne corrispondenti al risultato per le colonne di <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span>. </p><p>Esempio di una left outer join: </p> <div class="mw-highlight mw-highlight-lang-sql mw-content-ltr mw-highlight-lines" dir="ltr"><pre><span></span><span class="linenos" data-line="1"></span><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span><span class="w"> </span> <span class="linenos" data-line="2"></span><span class="k">FROM</span><span class="w"> </span><span class="n">Impiegati</span><span class="w"> </span><span class="k">LEFT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="w"> </span> <span class="linenos" data-line="3"></span><span class="w"> </span><span class="k">ON</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">.</span><span class="n">ID_dipartimento</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="p">.</span><span class="n">ID_dipartimento</span> </pre></div> <table class="wikitable" style="text-align:center"> <tbody><tr> <th>Impiegati.Cognome</th> <th>Impiegati.ID_dipartimento</th> <th>Dipartimenti.Nome_dipartimento</th> <th>Dipartimenti.ID_dipartimento </th></tr> <tr> <td>Bianchi</td> <td>33</td> <td>Tecnico</td> <td>33 </td></tr> <tr> <td>Rossi</td> <td>31</td> <td>Vendite</td> <td>31 </td></tr> <tr> <td>Santoro</td> <td>34</td> <td>Risorse umane</td> <td>34 </td></tr> <tr> <td>Monti</td> <td>34</td> <td>Risorse umane</td> <td>34 </td></tr> <tr> <td>Grassi</td> <td><code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code></td> <td><code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code></td> <td><code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code> </td></tr> <tr> <td>Mancini</td> <td>33</td> <td>Tecnico</td> <td>33 </td></tr></tbody></table> <div class="mw-heading mw-heading3"><h3 id="Right_outer_join">Right outer join</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Join_(SQL)&veaction=edit&section=9" title="Modifica la sezione Right outer join" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Join_(SQL)&action=edit&section=9" title="Edit section's source code: Right outer join"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:SQL_Join_-_03b_A_Right_Join_B.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/89/SQL_Join_-_03b_A_Right_Join_B.svg/220px-SQL_Join_-_03b_A_Right_Join_B.svg.png" decoding="async" width="220" height="149" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/89/SQL_Join_-_03b_A_Right_Join_B.svg/330px-SQL_Join_-_03b_A_Right_Join_B.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/89/SQL_Join_-_03b_A_Right_Join_B.svg/440px-SQL_Join_-_03b_A_Right_Join_B.svg.png 2x" data-file-width="234" data-file-height="158" /></a><figcaption><a href="/wiki/Diagramma_di_Venn" title="Diagramma di Venn">Diagramma di Venn</a> che rappresenta la <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">RIGHT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> di due tabelle</figcaption></figure> <p>Una <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">RIGHT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> (o <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">RIGHT</span><span class="w"> </span><span class="k">JOIN</span></code>) semplicemente ricalca il funzionamento della <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">LEFT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code>, ma invertendo l'ordine delle tabelle interessate. </p><p>Il risultato di una query <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">RIGHT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> per le tabelle <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span> e <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span> contiene sempre tutti i record della tabella di destra (<i>right</i>) <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span>, mentre vengono estratti dalla tabella di sinistra (<i>left</i>) <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span> solamente le righe che trovano corrispondenza nella regola di confronto della <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">JOIN</span></code>. Questo significa che se la clausola <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">ON</span></code> trova zero righe in <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span>, la <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">JOIN</span></code> mostrerà una riga risultante con valore <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code> in tutte le colonne corrispondenti al risultato per le colonne di <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span>. </p><p>Esempio di una <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">RIGHT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code>: </p> <div class="mw-highlight mw-highlight-lang-sql mw-content-ltr mw-highlight-lines" dir="ltr"><pre><span></span><span class="linenos" data-line="1"></span><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span><span class="w"> </span> <span class="linenos" data-line="2"></span><span class="k">FROM</span><span class="w"> </span><span class="n">Impiegati</span><span class="w"> </span><span class="k">RIGHT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="w"> </span> <span class="linenos" data-line="3"></span><span class="w"> </span><span class="k">ON</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">.</span><span class="n">ID_dipartimento</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="p">.</span><span class="n">ID_dipartimento</span> </pre></div> <table class="wikitable" style="text-align:center"> <tbody><tr> <th>Impiegati.Cognome</th> <th>Impiegati.ID_dipartimento</th> <th>Dipartimenti.Nome_dipartimento</th> <th>Dipartimenti.ID_dipartimento </th></tr> <tr> <td>Monti</td> <td>34</td> <td>Risorse umane</td> <td>34 </td></tr> <tr> <td>Bianchi</td> <td>33</td> <td>Tecnico</td> <td>33 </td></tr> <tr> <td>Santoro</td> <td>34</td> <td>Risorse umane</td> <td>34 </td></tr> <tr> <td>Mancini</td> <td>33</td> <td>Tecnico</td> <td>33 </td></tr> <tr> <td>Rossi</td> <td>31</td> <td>Vendite</td> <td>31 </td></tr> <tr> <td><code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code></td> <td><code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code></td> <td>Promozione</td> <td>35 </td></tr></tbody></table> <p>In pratica sono utilizzate maggiormente le query di <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">LEFT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> rispetto a quelle di <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">RIGHT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code>, ma possono verificarsi rari casi in cui in query molto complesse ci sia la necessità di utilizzare contemporaneamente il criterio di <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">LEFT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> e di <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">RIGHT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code>. </p><p>Lo stesso risultato della precedente <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">RIGHT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> si può ripetere usando il tipo <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">LEFT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code>: </p> <div class="mw-highlight mw-highlight-lang-sql mw-content-ltr mw-highlight-lines" dir="ltr"><pre><span></span><span class="linenos" data-line="1"></span><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span><span class="w"> </span> <span class="linenos" data-line="2"></span><span class="k">FROM</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="w"> </span><span class="k">LEFT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span><span class="w"> </span><span class="n">Impiegati</span> <span class="linenos" data-line="3"></span><span class="w"> </span><span class="k">ON</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">.</span><span class="n">ID_dipartimento</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="p">.</span><span class="n">ID_dipartimento</span> </pre></div> <div class="mw-heading mw-heading3"><h3 id="Full_outer_join">Full outer join</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Join_(SQL)&veaction=edit&section=10" title="Modifica la sezione Full outer join" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Join_(SQL)&action=edit&section=10" title="Edit section's source code: Full outer join"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:SQL_Join_-_05b_A_Full_Join_B.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/3d/SQL_Join_-_05b_A_Full_Join_B.svg/220px-SQL_Join_-_05b_A_Full_Join_B.svg.png" decoding="async" width="220" height="149" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/3d/SQL_Join_-_05b_A_Full_Join_B.svg/330px-SQL_Join_-_05b_A_Full_Join_B.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/3d/SQL_Join_-_05b_A_Full_Join_B.svg/440px-SQL_Join_-_05b_A_Full_Join_B.svg.png 2x" data-file-width="234" data-file-height="158" /></a><figcaption><a href="/wiki/Diagramma_di_Venn" title="Diagramma di Venn">Diagramma di Venn</a> che rappresenta la <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">FULL</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> di due tabelle</figcaption></figure> <p>Una <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">FULL</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> combina i risultati delle due tabelle <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span> e <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span> tenendo conto di tutte le righe delle tabelle, anche di quelle che non hanno corrispondenza tra di loro. </p><p>Il risultato di una query <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">FULL</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> per le tabelle <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span> e <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span> contiene sempre tutti i record della tabella di sinistra (<i>left</i>) <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span>, estraendo dalla tabella di destra (<i>right</i>) <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span> solamente le righe che trovano corrispondenza nella regola di confronto della join; inoltre verranno estratti tutti i record della tabella di sinistra (<i>left</i>) <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span> che non trovano corrispondenza nella tabella di destra (<i>right</i>) <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span> impostando a <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code> i valori di tutte le colonne della tabella <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span> e tutti i record della tabella di destra (<i>right</i>) <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle B}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>B</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle B}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/47136aad860d145f75f3eed3022df827cee94d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle B}" /></span> che non trovano corrispondenza nella tabella di sinistra (<i>left</i>) <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span> impostando a <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code> i valori di tutte le colonne della tabella <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle A}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>A</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle A}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7daff47fa58cdfd29dc333def748ff5fa4c923e3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle A}" /></span>. </p><p>Esempio di una <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">FULL</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code>: </p> <div class="mw-highlight mw-highlight-lang-sql mw-content-ltr mw-highlight-lines" dir="ltr"><pre><span></span><span class="linenos" data-line="1"></span><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span><span class="w"> </span> <span class="linenos" data-line="2"></span><span class="k">FROM</span><span class="w"> </span><span class="n">Impiegati</span><span class="w"> </span> <span class="linenos" data-line="3"></span><span class="w"> </span><span class="k">FULL</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="w"> </span> <span class="linenos" data-line="4"></span><span class="w"> </span><span class="k">ON</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">.</span><span class="n">ID_dipartimento</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="p">.</span><span class="n">ID_dipartimento</span> </pre></div> <table class="wikitable" style="text-align:center"> <tbody><tr> <th>Impiegati.Cognome</th> <th>Impiegati.ID_dipartimento</th> <th>Dipartimenti.Nome_dipartimento</th> <th>Dipartimenti.ID_dipartimento </th></tr> <tr> <td>Monti</td> <td>34</td> <td>Risorse umane</td> <td>34 </td></tr> <tr> <td>Bianchi</td> <td>33</td> <td>Tecnico</td> <td>33 </td></tr> <tr> <td>Santoro</td> <td>34</td> <td>Risorse umane</td> <td>34 </td></tr> <tr> <td><i>Grassi</i></td> <td><code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code></td> <td><code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code></td> <td><code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code> </td></tr> <tr> <td>Mancini</td> <td>33</td> <td>Tecnico</td> <td>33 </td></tr> <tr> <td>Rossi</td> <td>31</td> <td>Vendite</td> <td>31 </td></tr> <tr> <td><code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code></td> <td><code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">NULL</span></code></td> <td><i>Promozione</i></td> <td><i>35</i> </td></tr></tbody></table> <p>Alcuni database (come per esempio MySQL) non supportano direttamente questa funzionalità, ma la si può emulare attraverso la combinazione di <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">LEFT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> e <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">RIGHT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> per mezzo della parola riservata <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">UNION</span></code>. </p><p>La creazione di una query di <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">FULL</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code> si realizzerà come segue: </p> <div class="mw-highlight mw-highlight-lang-sql mw-content-ltr mw-highlight-lines" dir="ltr"><pre><span></span><span class="linenos" data-line="1"></span><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span> <span class="linenos" data-line="2"></span><span class="k">FROM</span><span class="w"> </span><span class="n">Impiegati</span><span class="w"> </span> <span class="linenos" data-line="3"></span><span class="w"> </span><span class="k">LEFT</span><span class="w"> </span><span class="k">JOIN</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="w"> </span> <span class="linenos" data-line="4"></span><span class="w"> </span><span class="k">ON</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">.</span><span class="n">ID_dipartimento</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="p">.</span><span class="n">ID_dipartimento</span> <span class="linenos" data-line="5"></span><span class="k">UNION</span> <span class="linenos" data-line="6"></span><span class="k">SELECT</span><span class="w"> </span><span class="o">*</span> <span class="linenos" data-line="7"></span><span class="k">FROM</span><span class="w"> </span><span class="n">Impiegati</span> <span class="linenos" data-line="8"></span><span class="w"> </span><span class="k">RIGHT</span><span class="w"> </span><span class="k">JOIN</span><span class="w"> </span><span class="n">Dipartimenti</span> <span class="linenos" data-line="9"></span><span class="w"> </span><span class="k">ON</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">.</span><span class="n">ID_dipartimento</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="p">.</span><span class="n">ID_dipartimento</span> <span class="linenos" data-line="10"></span><span class="k">WHERE</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">.</span><span class="n">ID_dipartimento</span><span class="w"> </span><span class="k">IS</span><span class="w"> </span><span class="k">NULL</span> </pre></div> <p>Allo stesso modo senza utilizzare nemmeno la query di <code class="mw-highlight mw-highlight-lang-sql mw-content-ltr" dir="ltr"><span class="k">RIGHT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span></code>: </p> <div class="mw-highlight mw-highlight-lang-sql mw-content-ltr mw-highlight-lines" dir="ltr"><pre><span></span><span class="linenos" data-line="1"></span><span class="k">SELECT</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">.</span><span class="o">*</span><span class="p">,</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="p">.</span><span class="o">*</span> <span class="linenos" data-line="2"></span><span class="k">FROM</span><span class="w"> </span><span class="n">Impiegati</span><span class="w"> </span> <span class="linenos" data-line="3"></span><span class="w"> </span><span class="k">LEFT</span><span class="w"> </span><span class="k">JOIN</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="w"> </span> <span class="linenos" data-line="4"></span><span class="w"> </span><span class="k">ON</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">.</span><span class="n">ID_dipartimento</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="p">.</span><span class="n">ID_dipartimento</span> <span class="linenos" data-line="5"></span><span class="k">UNION</span> <span class="linenos" data-line="6"></span><span class="k">SELECT</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">.</span><span class="o">*</span><span class="p">,</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="p">.</span><span class="o">*</span> <span class="linenos" data-line="7"></span><span class="k">FROM</span><span class="w"> </span><span class="n">Dipartimenti</span> <span class="linenos" data-line="8"></span><span class="w"> </span><span class="k">LEFT</span><span class="w"> </span><span class="k">JOIN</span><span class="w"> </span><span class="n">Impiegati</span> <span class="linenos" data-line="9"></span><span class="w"> </span><span class="k">ON</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">.</span><span class="n">ID_dipartimento</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Dipartimenti</span><span class="p">.</span><span class="n">ID_dipartimento</span> <span class="linenos" data-line="10"></span><span class="k">WHERE</span><span class="w"> </span><span class="n">Impiegati</span><span class="p">.</span><span class="n">ID_dipartimento</span><span class="w"> </span><span class="k">IS</span><span class="w"> </span><span class="k">NULL</span> </pre></div> <div class="mw-heading mw-heading2"><h2 id="Self-join">Self-join</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Join_(SQL)&veaction=edit&section=11" title="Modifica la sezione Self-join" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Join_(SQL)&action=edit&section=11" title="Edit section's source code: Self-join"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>La <i>self-join</i> serve a unire una tabella con se stessa. </p> <div class="mw-heading mw-heading2"><h2 id="Voci_correlate">Voci correlate</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Join_(SQL)&veaction=edit&section=12" title="Modifica la sezione Voci correlate" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Join_(SQL)&action=edit&section=12" title="Edit section's source code: Voci correlate"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Sort_merge_join" title="Sort merge join">Sort merge join</a></li> <li><a href="/wiki/SQL" class="mw-redirect" title="SQL">SQL</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Altri_progetti">Altri progetti</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Join_(SQL)&veaction=edit&section=13" title="Modifica la sezione Altri progetti" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Join_(SQL)&action=edit&section=13" title="Edit section's source code: Altri progetti"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <div id="interProject" class="toccolours" style="display: none; clear: both; margin-top: 2em"><p id="sisterProjects" style="background-color: #efefef; color: black; font-weight: bold; margin: 0"><span>Altri progetti</span></p><ul title="Collegamenti verso gli altri progetti Wikimedia"> <li class="" title=""><span class="plainlinks" title="commons:Category:SQL Joins"><a class="external text" href="https://commons.wikimedia.org/wiki/Category:SQL_Joins?uselang=it">Wikimedia Commons</a></span></li></ul></div> <ul><li><span typeof="mw:File"><a href="https://commons.wikimedia.org/wiki/?uselang=it" title="Collabora a Wikimedia Commons"><img alt="Collabora a Wikimedia Commons" src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Commons-logo.svg/18px-Commons-logo.svg.png" decoding="async" width="18" height="24" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Commons-logo.svg/27px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Commons-logo.svg/36px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /></a></span> <span class="plainlinks"><a class="external text" href="https://commons.wikimedia.org/wiki/?uselang=it">Wikimedia Commons</a></span> contiene immagini o altri file sulla <b><span class="plainlinks"><a class="external text" href="https://commons.wikimedia.org/wiki/Category:SQL_Joins?uselang=it">join</a></span></b></li></ul> <div class="mw-heading mw-heading2"><h2 id="Collegamenti_esterni">Collegamenti esterni</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Join_(SQL)&veaction=edit&section=14" title="Modifica la sezione Collegamenti esterni" class="mw-editsection-visualeditor"><span>modifica</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Join_(SQL)&action=edit&section=14" title="Edit section's source code: Collegamenti esterni"><span>modifica wikitesto</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><cite id="CITEREFFOLDOC" class="citation testo" style="font-style:normal">(<span style="font-weight:bolder; font-size:80%"><abbr title="inglese">EN</abbr></span>) Denis Howe, <span style="font-style:italic;"><a href="https://foldoc.org/Join" class="extiw" title="foldoc:Join">join</a></span>, in <span style="font-style:italic;"><a href="/wiki/Free_On-line_Dictionary_of_Computing" title="Free On-line Dictionary of Computing">Free On-line Dictionary of Computing</a></span>.</cite> Disponibile con licenza <a href="/wiki/GNU_Free_Documentation_License" title="GNU Free Documentation License">GFDL</a></li> <li><cite class="citation web" style="font-style:normal"> <a rel="nofollow" class="external text" href="https://archive.is/20121220173307/https://kb.askmonty.org/it/introduzione-alle-join/"><span style="font-style:italic;">Introduzione alle JOIN (nella knowledgebase di AskMonty)</span></a>, su <span style="font-style:italic;">kb.askmonty.org</span>. <small>URL consultato il 18 ottobre 2022</small> <small>(archiviato dall'<abbr title="https://kb.askmonty.org/it/introduzione-alle-join/">url originale</abbr> il 20 dicembre 2012)</small>.</cite></li></ul> <style data-mw-deduplicate="TemplateStyles:r141815314">.mw-parser-output .navbox{border:1px solid #aaa;clear:both;margin:auto;padding:2px;width:100%}.mw-parser-output .navbox th{padding-left:1em;padding-right:1em;text-align:center}.mw-parser-output .navbox>tbody>tr:first-child>th{background:#ccf;font-size:90%;width:100%;color:var(--color-base,black)}.mw-parser-output .navbox_navbar{float:left;margin:0;padding:0 10px 0 0;text-align:left;width:6em}.mw-parser-output .navbox_title{font-size:110%}.mw-parser-output .navbox_abovebelow{background:#ddf;font-size:90%;font-weight:normal}.mw-parser-output .navbox_group{background:#ddf;font-size:90%;padding:0 10px;white-space:nowrap}.mw-parser-output .navbox_list{font-size:90%;width:100%}.mw-parser-output .navbox_list a{white-space:nowrap}html:not(.vector-feature-night-mode-enabled) .mw-parser-output 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