{"id":200314,"date":"2023-06-13T07:30:00","date_gmt":"2023-06-13T07:30:00","guid":{"rendered":"https:\/\/datascientest.com\/?p=200314"},"modified":"2023-11-09T13:52:06","modified_gmt":"2023-11-09T13:52:06","slug":"cle-primaire-tout-savoir","status":"publish","type":"post","link":"https:\/\/datascientest.com\/cle-primaire-tout-savoir","title":{"rendered":"Cl\u00e9 primaire : D\u00e9finition, avantages et particularit\u00e9s"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"200314\" class=\"elementor elementor-200314\" data-elementor-post-type=\"post\">\n\t\t\t\t\t\t\t<div class=\"elementor-element elementor-element-44d0026 e-flex e-con-boxed e-con\" data-id=\"44d0026\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-72b28cf elementor-widget elementor-widget-heading\" data-id=\"72b28cf\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<style>\/*! elementor - v3.15.0 - 02-08-2023 *\/\n.elementor-heading-title{padding:0;margin:0;line-height:1}.elementor-widget-heading .elementor-heading-title[class*=elementor-size-]>a{color:inherit;font-size:inherit;line-height:inherit}.elementor-widget-heading .elementor-heading-title.elementor-size-small{font-size:15px}.elementor-widget-heading .elementor-heading-title.elementor-size-medium{font-size:19px}.elementor-widget-heading .elementor-heading-title.elementor-size-large{font-size:29px}.elementor-widget-heading .elementor-heading-title.elementor-size-xl{font-size:39px}.elementor-widget-heading .elementor-heading-title.elementor-size-xxl{font-size:59px}<\/style><h2 class=\"elementor-heading-title elementor-size-default\">Les bases de donn\u00e9es relationnelles contiennent des milliers et des milliers de lignes. Pour en simplifier le traitement, il est primordial d\u2019identifier de mani\u00e8re claire et efficace les diff\u00e9rents enregistrements d\u2019une table. C\u2019est \u00e0 cet instant qu\u2019interviennent les cl\u00e9s primaires. <\/h2>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-aa17ed2 e-flex e-con-boxed e-con\" data-id=\"aa17ed2\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-0e99b77 elementor-widget elementor-widget-heading\" data-id=\"0e99b77\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Les cl\u00e9s primaires, des champs uniques sur votre table de donn\u00e9es<\/h3>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-f2c862e elementor-widget elementor-widget-text-editor\" data-id=\"f2c862e\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<style>\/*! elementor - v3.15.0 - 02-08-2023 *\/\n.elementor-widget-text-editor.elementor-drop-cap-view-stacked .elementor-drop-cap{background-color:#69727d;color:#fff}.elementor-widget-text-editor.elementor-drop-cap-view-framed .elementor-drop-cap{color:#69727d;border:3px solid;background-color:transparent}.elementor-widget-text-editor:not(.elementor-drop-cap-view-default) .elementor-drop-cap{margin-top:8px}.elementor-widget-text-editor:not(.elementor-drop-cap-view-default) .elementor-drop-cap-letter{width:1em;height:1em}.elementor-widget-text-editor .elementor-drop-cap{float:left;text-align:center;line-height:1;font-size:50px}.elementor-widget-text-editor .elementor-drop-cap-letter{display:inline-block}<\/style>\t\t\t\t<p><span style=\"font-weight: 400;\">La cl\u00e9 primaire renvoie \u00e0 un (ou plusieurs) attribut(s) qui permet(tent) d\u2019en diff\u00e9rencier totalement les enregistrements. Concr\u00e8tement, il s\u2019agit d\u2019un <\/span><b>champ unique pour tous les enregistrements dans une table.<\/b><\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-c6c849b elementor-widget elementor-widget-heading\" data-id=\"c6c849b\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<h4 class=\"elementor-heading-title elementor-size-default\">Les avantages d\u2019une cl\u00e9 primaire<\/h4>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-396260c elementor-widget elementor-widget-text-editor\" data-id=\"396260c\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">L\u2019objectif des cl\u00e9s primaires est de structurer la base de donn\u00e9es pour identifier plus facilement les lignes du tableau. Ce faisant, les primary keys permettent de :\u00a0<\/span><\/p><ul><li style=\"font-weight: 400;\" aria-level=\"1\"><b>Garantir l&rsquo;int\u00e9grit\u00e9 et l&rsquo;exactitude des donn\u00e9es :<\/b><span style=\"font-weight: 400;\"> chaque ligne n&rsquo;est enregistr\u00e9e qu&rsquo;une seule fois et aucune information importante n&rsquo;est perdue.<\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><b>Simplifier le processus de mise \u00e0 jour <\/b><span style=\"font-weight: 400;\">: il suffit de s\u00e9lectionner les diff\u00e9rentes cl\u00e9s primaires pour modifier ou supprimer des lignes.<\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><b>Acc\u00e9der plus rapidement aux donn\u00e9es<\/b><span> : si vous connaissez la cl\u00e9 primaire de la table, vous pouvez plus facilement acc\u00e9der aux<\/span> <a href=\"https:\/\/datascientest.com\/la-data-le-nouvel-or-du-21eme-siecle\">donn\u00e9es<\/a><span>qui vous int\u00e9ressent.<\/span><\/li><\/ul>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-9dceed1 elementor-align-center button-principale elementor-widget elementor-widget-button\" data-id=\"9dceed1\" data-element_type=\"widget\" data-widget_type=\"button.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<div class=\"elementor-button-wrapper\">\n\t\t\t<a class=\"elementor-button elementor-button-link elementor-size-sm elementor-animation-grow\" href=\"https:\/\/datascientest.com\/formation-sql\">\n\t\t\t\t\t\t<span class=\"elementor-button-content-wrapper\">\n\t\t\t\t\t\t<span class=\"elementor-button-text\">Apprendre \u00e0 utiliser les cl\u00e9s primaires<\/span>\n\t\t<\/span>\n\t\t\t\t\t<\/a>\n\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-8abdac2 elementor-widget elementor-widget-heading\" data-id=\"8abdac2\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<h4 class=\"elementor-heading-title elementor-size-default\">Exemple de primary key<\/h4>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-88568b0 elementor-widget elementor-widget-text-editor\" data-id=\"88568b0\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">Pour vous aider \u00e0 mieux comprendre les cl\u00e9s primaires, voici un exemple : <\/span><\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-318313d elementor-widget elementor-widget-html\" data-id=\"318313d\" data-element_type=\"widget\" data-widget_type=\"html.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<style type=\"text\/css\">\r\n.tg  {border-collapse:collapse;border-spacing:0;}\r\n.tg td{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px;\r\n  overflow:hidden;padding:10px 5px;word-break:normal;}\r\n.tg th{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px;\r\n  font-weight:normal;overflow:hidden;padding:10px 5px;word-break:normal;}\r\n.tg .tg-z2m2{background-color:#6434fc;color:#efefef;font-family:\"Trebuchet MS\", Helvetica, sans-serif !important;font-size:20px;\r\n  font-weight:bold;text-align:center;vertical-align:top}\r\n.tg .tg-4lje{font-family:\"Trebuchet MS\", Helvetica, sans-serif !important;text-align:center;vertical-align:top}\r\n<\/style>\r\n<table class=\"tg\" style=\"undefined;table-layout: fixed; width: 250px\">\r\n<colgroup>\r\n<col style=\"width: 100px\">\r\n<col style=\"width: 100px\">\r\n<col style=\"width: 50px\">\r\n<\/colgroup>\r\n<thead>\r\n  <tr>\r\n    <th class=\"tg-z2m2\">Nom<\/th>\r\n    <th class=\"tg-z2m2\">Pr\u00e9nom<\/th>\r\n    <th class=\"tg-z2m2\">\u00c2ge<\/th>\r\n  <\/tr>\r\n<\/thead>\r\n<tbody>\r\n  <tr>\r\n    <td class=\"tg-4lje\">Dupont<\/td>\r\n    <td class=\"tg-4lje\">Jeanne<\/td>\r\n    <td class=\"tg-4lje\">25<\/td>\r\n  <\/tr>\r\n  <tr>\r\n    <td class=\"tg-4lje\">Leroy<\/td>\r\n    <td class=\"tg-4lje\">Marie<\/td>\r\n    <td class=\"tg-4lje\">21<\/td>\r\n  <\/tr>\r\n  <tr>\r\n    <td class=\"tg-4lje\">Dupont <\/td>\r\n    <td class=\"tg-4lje\">Pierre<\/td>\r\n    <td class=\"tg-4lje\">21<\/td>\r\n  <\/tr>\r\n<\/tbody>\r\n<\/table>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-78d165f elementor-widget elementor-widget-text-editor\" data-id=\"78d165f\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">Dans cet exemple, seul l\u2019attribut \u00ab\u00a0Pr\u00e9nom\u00a0\u00bb permet de diff\u00e9rencier les lignes de la table. Et pour cause, dans le nom, \u00ab\u00a0Dupont\u00a0\u00bb se retrouve \u00e0 2 reprises. Idem pour l&rsquo;\u00e2ge 21. L\u2019attribut pr\u00e9nom est donc une cl\u00e9 primaire.\u00a0<\/span><\/p><p><span style=\"font-weight: 400;\">En revanche, ce n\u2019est plus le cas avec le tableau suivant :<\/span><\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-745b755 elementor-widget elementor-widget-html\" data-id=\"745b755\" data-element_type=\"widget\" data-widget_type=\"html.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<style type=\"text\/css\">\r\n.tg  {border-collapse:collapse;border-spacing:0;}\r\n.tg td{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px;\r\n  overflow:hidden;padding:10px 5px;word-break:normal;}\r\n.tg th{border-color:black;border-style:solid;border-width:1px;font-family:Arial, sans-serif;font-size:14px;\r\n  font-weight:normal;overflow:hidden;padding:10px 5px;word-break:normal;}\r\n.tg .tg-z2m2{background-color:#6434fc;color:#efefef;font-family:\"Trebuchet MS\", Helvetica, sans-serif !important;font-size:20px;\r\n  font-weight:bold;text-align:center;vertical-align:top}\r\n.tg .tg-4lje{font-family:\"Trebuchet MS\", Helvetica, sans-serif !important;text-align:center;vertical-align:top}\r\n<\/style>\r\n<table class=\"tg\" style=\"undefined;table-layout: fixed; width: 250px\">\r\n<colgroup>\r\n<col style=\"width: 100px\">\r\n<col style=\"width: 100px\">\r\n<col style=\"width: 50px\">\r\n<\/colgroup>\r\n<thead>\r\n  <tr>\r\n    <th class=\"tg-z2m2\">Nom<\/th>\r\n    <th class=\"tg-z2m2\">Pr\u00e9nom<\/th>\r\n    <th class=\"tg-z2m2\">\u00c2ge<\/th>\r\n  <\/tr>\r\n<\/thead>\r\n<tbody>\r\n  <tr>\r\n    <td class=\"tg-4lje\">Dupont<\/td>\r\n    <td class=\"tg-4lje\">Jeanne<\/td>\r\n    <td class=\"tg-4lje\">25<\/td>\r\n  <\/tr>\r\n  <tr>\r\n    <td class=\"tg-4lje\">Leroy<\/td>\r\n    <td class=\"tg-4lje\">Jeanne<\/td>\r\n    <td class=\"tg-4lje\">21<\/td>\r\n  <\/tr>\r\n  <tr>\r\n    <td class=\"tg-4lje\">Dupont <\/td>\r\n    <td class=\"tg-4lje\">Pierre<\/td>\r\n    <td class=\"tg-4lje\">21<\/td>\r\n  <\/tr>\r\n<\/tbody>\r\n<\/table>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-38ec34e elementor-widget elementor-widget-text-editor\" data-id=\"38ec34e\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">Dans ce cas, aucun attribut ne permet \u00e0 lui seul de diff\u00e9rencier les enregistrements. Il convient donc de s\u00e9lectionner plusieurs attributs, comme nom + pr\u00e9nom. En combinant les deux, on voit bien qu\u2019il n\u2019y a jamais deux fois la m\u00eame ligne. Ici, les attributs nom + pr\u00e9nom constituent une cl\u00e9 primaire.<\/span><\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-2b99edf elementor-widget elementor-widget-text-editor\" data-id=\"2b99edf\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p><span style=\"text-decoration: underline;\"><strong>Bon \u00e0 savoir <\/strong><\/span><span style=\"font-weight: 400;\"><span style=\"text-decoration: underline;\"><strong>:<\/strong><\/span> bien souvent, les bases de donn\u00e9es contiennent <\/span><b>un attribut ID qui sert de cl\u00e9 primaire<\/b><span style=\"font-weight: 400;\">. Il s\u2019agit d\u2019attribuer un num\u00e9ro distinct pour chaque ligne (1,2,3,4&#8230;). Cette cl\u00e9 primaire se cr\u00e9e automatiquement au tout d\u00e9but de la table (colonne A) afin de diff\u00e9rencier chaque enregistrement.\u00a0<\/span><\/p><p><span style=\"font-weight: 400;\">C\u2019est pour cette raison que le terme <\/span><b>cl\u00e9 primaire<\/b><span style=\"font-weight: 400;\"> est tr\u00e8s souvent confondu avec l\u2019identifiant. Alors si les deux sont souvent identiques, ce n\u2019est pas automatique.<\/span><\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-38aa63f e-flex e-con-boxed e-con\" data-id=\"38aa63f\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-2f38159 elementor-widget elementor-widget-heading\" data-id=\"2f38159\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Les diff\u00e9rents types de cl\u00e9s primaires<\/h3>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-a070e37 elementor-widget elementor-widget-text-editor\" data-id=\"a070e37\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">Il existe diff\u00e9rents types de cl\u00e9s primaires. Les plus courants sont :\u00a0<\/span><\/p><ul><li style=\"font-weight: 400;\" aria-level=\"1\"><b>Les cl\u00e9s naturelles <\/b><span style=\"font-weight: 400;\">: ce sont les attributs qui contiennent des informations significatives (sans lesquelles il n\u2019est pas possible de se tromper). C\u2019est par exemple le cas d\u2019un num\u00e9ro de s\u00e9curit\u00e9 sociale.\u00a0<\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><b>Les cl\u00e9s de substitution<\/b><span style=\"font-weight: 400;\"> : il s\u2019agit d\u2019une cl\u00e9 artificielle, comme un num\u00e9ro g\u00e9n\u00e9r\u00e9 automatiquement.<\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><b>Les cl\u00e9s composites<\/b><span> : c\u2019est la combinaison de plusieurs attributs, comme le nom et le pr\u00e9nom des clients.<\/span><\/li><\/ul>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-f06ef4e e-flex e-con-boxed e-con\" data-id=\"f06ef4e\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-019c835 elementor-widget elementor-widget-heading\" data-id=\"019c835\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Les cl\u00e9s primaires et les cl\u00e9s \u00e9trang\u00e8res<\/h3>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-9869988 elementor-widget elementor-widget-text-editor\" data-id=\"9869988\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">L\u2019objectif final de la cl\u00e9 primaire est de<\/span><b> relier les enregistrements li\u00e9s dans d&rsquo;autres tables<\/b><span style=\"font-weight: 400;\">. Par exemple, l\u2019identifiant ID des clients peut \u00eatre utilis\u00e9 dans une table regroupant l\u2019ensemble des clients de l\u2019entreprise et une autre table regroupant les clients par commerciaux.\u00a0<\/span><\/p><p><span style=\"font-weight: 400;\">C\u2019est l\u00e0 qu\u2019interviennent les <\/span><b>cl\u00e9s \u00e9trang\u00e8res<\/b><span style=\"font-weight: 400;\">. Il s\u2019agit d\u2019un ou plusieurs attributs qui sont cl\u00e9 primaire dans une table A et qui servent \u00e0 caract\u00e9riser les \u00e9l\u00e9ments dans une table B. Dans cette hypoth\u00e8se, c\u2019est g\u00e9n\u00e9ralement l\u2019ID (d\u2019un client, d\u2019un produit, d\u2019un collaborateur\u2026) qui est utilis\u00e9 dans plusieurs tables diff\u00e9rentes.\u00a0<\/span><\/p><p><span style=\"font-weight: 400;\">Vous souhaitez en savoir plus sur la gestion des donn\u00e9es, <strong>inscrivez-vous \u00e0 l&rsquo;une de nos formations<\/strong>.\u00a0<\/span><\/p>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d308784 elementor-widget__width-initial elementor-widget elementor-widget-video\" data-id=\"d308784\" data-element_type=\"widget\" data-settings=\"{&quot;youtube_url&quot;:&quot;https:\\\/\\\/youtu.be\\\/iCFPnkBwmNk&quot;,&quot;video_type&quot;:&quot;youtube&quot;,&quot;controls&quot;:&quot;yes&quot;}\" data-widget_type=\"video.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<style>\/*! elementor - v3.15.0 - 02-08-2023 *\/\n.elementor-widget-video .elementor-widget-container{overflow:hidden;transform:translateZ(0)}.elementor-widget-video .elementor-wrapper{aspect-ratio:var(--video-aspect-ratio)}.elementor-widget-video .elementor-wrapper iframe,.elementor-widget-video .elementor-wrapper video{height:100%;width:100%;display:flex;border:none;background-color:#000}@supports not (aspect-ratio:1\/1){.elementor-widget-video .elementor-wrapper{position:relative;overflow:hidden;height:0;padding-bottom:calc(100% \/ var(--video-aspect-ratio))}.elementor-widget-video .elementor-wrapper iframe,.elementor-widget-video .elementor-wrapper video{position:absolute;top:0;right:0;bottom:0;left:0}}.elementor-widget-video .elementor-open-inline .elementor-custom-embed-image-overlay{position:absolute;top:0;right:0;bottom:0;left:0;background-size:cover;background-position:50%}.elementor-widget-video .elementor-custom-embed-image-overlay{cursor:pointer;text-align:center}.elementor-widget-video .elementor-custom-embed-image-overlay:hover .elementor-custom-embed-play i{opacity:1}.elementor-widget-video .elementor-custom-embed-image-overlay img{display:block;width:100%;aspect-ratio:var(--video-aspect-ratio);-o-object-fit:cover;object-fit:cover;-o-object-position:center center;object-position:center center}@supports not (aspect-ratio:1\/1){.elementor-widget-video .elementor-custom-embed-image-overlay{position:relative;overflow:hidden;height:0;padding-bottom:calc(100% \/ var(--video-aspect-ratio))}.elementor-widget-video .elementor-custom-embed-image-overlay img{position:absolute;top:0;right:0;bottom:0;left:0}}.elementor-widget-video .e-hosted-video .elementor-video{-o-object-fit:cover;object-fit:cover}.e-con-inner>.elementor-widget-video,.e-con>.elementor-widget-video{width:var(--container-widget-width);--flex-grow:var(--container-widget-flex-grow)}<\/style>\t\t<div class=\"elementor-wrapper elementor-open-inline\">\n\t\t\t<div class=\"elementor-video\"><\/div>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-4a06b2a elementor-align-center button-principale elementor-widget elementor-widget-button\" data-id=\"4a06b2a\" data-element_type=\"widget\" data-widget_type=\"button.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t<div class=\"elementor-button-wrapper\">\n\t\t\t<a class=\"elementor-button elementor-button-link elementor-size-sm elementor-animation-grow\" href=\"https:\/\/datascientest.com\/formation-sql\">\n\t\t\t\t\t\t<span class=\"elementor-button-content-wrapper\">\n\t\t\t\t\t\t<span class=\"elementor-button-text\">Rejoindre les formations de DataScientest<\/span>\n\t\t<\/span>\n\t\t\t\t\t<\/a>\n\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-0f35d46 e-flex e-con-boxed e-con\" data-id=\"0f35d46\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-e8faaeb elementor-widget elementor-widget-heading\" data-id=\"e8faaeb\" data-element_type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Ce qu\u2019il faut retenir :<\/h3>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-194616c elementor-widget elementor-widget-text-editor\" data-id=\"194616c\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t<ul><li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Les cl\u00e9s primaires repr\u00e9sentent des champs uniques permettant de diff\u00e9rencier les lignes d\u2019une base de donn\u00e9es.\u00a0<\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">La plupart du temps, les cl\u00e9s primaires sont les ID (ou identifiants). Mais ce n\u2019est pas syst\u00e9matique.\u00a0<\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Pour relier les donn\u00e9es entre diff\u00e9rentes tables, les cl\u00e9s \u00e9trang\u00e8res sont utilis\u00e9es. <\/span><\/li><\/ul>\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-52f94b3 e-flex e-con-boxed e-con\" data-id=\"52f94b3\" data-element_type=\"container\" data-settings=\"{&quot;content_width&quot;:&quot;boxed&quot;}\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-2a968f0 elementor-widget elementor-widget-html\" data-id=\"2a968f0\" data-element_type=\"widget\" data-widget_type=\"html.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t<script type=\"application\/ld+json\">\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@type\": \"FAQPage\",\n  \"mainEntity\": [{\n    \"@type\": \"Question\",\n    \"name\": \"Les cl\u00e9s primaires, des champs uniques sur votre table de donn\u00e9es\",\n    \"acceptedAnswer\": {\n      \"@type\": \"Answer\",\n      \"text\": \"La cl\u00e9 primaire renvoie \u00e0 un (ou plusieurs) attribut(s) qui permet(tent) d\u2019en diff\u00e9rencier totalement les enregistrements. Concr\u00e8tement, il s\u2019agit d\u2019un champ unique pour tous les enregistrements dans une table.\"\n    }\n  },{\n    \"@type\": \"Question\",\n    \"name\": \"Les cl\u00e9s primaires et les cl\u00e9s \u00e9trang\u00e8res\",\n    \"acceptedAnswer\": {\n      \"@type\": \"Answer\",\n      \"text\": \"L\u2019objectif final de la cl\u00e9 primaire est de relier les enregistrements li\u00e9s dans d'autres tables. Par exemple, l\u2019identifiant ID des clients peut \u00eatre utilis\u00e9 dans une table regroupant l\u2019ensemble des clients de l\u2019entreprise et une autre table regroupant les clients par commerciaux.\"\n    }\n  }]\n}\n<\/script>\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>Les bases de donn\u00e9es relationnelles contiennent des milliers et des milliers de lignes. Pour en simplifier le traitement, il est primordial d\u2019identifier de mani\u00e8re claire et efficace les diff\u00e9rents enregistrements d\u2019une table. C\u2019est \u00e0 cet instant qu\u2019interviennent les cl\u00e9s primaires. Les cl\u00e9s primaires, des champs uniques sur votre table de donn\u00e9es La cl\u00e9 primaire renvoie [&hellip;]<\/p>\n","protected":false},"author":77,"featured_media":200316,"comment_status":"open","ping_status":"open","sticky":false,"template":"elementor_theme","format":"standard","meta":{"content-type":"","inline_featured_image":false},"categories":[2497],"tags":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v21.7 (Yoast SEO v21.7) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Cl\u00e9 primaire : D\u00e9finition, avantages et particularit\u00e9s<\/title>\n<meta name=\"description\" content=\"Afin d\u2019identifier, sans \u00e9quivoque, les diff\u00e9rents enregistrements d\u2019une table, il y a les cl\u00e9s primaires. Focus.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/datascientest.com\/cle-primaire-tout-savoir\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Cl\u00e9 primaire : D\u00e9finition, avantages et particularit\u00e9s\" \/>\n<meta property=\"og:url\" content=\"https:\/\/datascientest.com\/cle-primaire-tout-savoir\" \/>\n<meta property=\"og:site_name\" content=\"Formation Data Science | DataScientest.com\" \/>\n<meta property=\"article:published_time\" content=\"2023-06-13T07:30:00+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2023-11-09T13:52:06+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/datascientest.com\/wp-content\/uploads\/2023\/05\/primary-keys.png\" \/>\n\t<meta property=\"og:image:width\" content=\"1200\" \/>\n\t<meta property=\"og:image:height\" content=\"600\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"author\" content=\"Raphael Kassel\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"\u00c9crit par\" \/>\n\t<meta name=\"twitter:data1\" content=\"Raphael Kassel\" \/>\n\t<meta name=\"twitter:label2\" content=\"Dur\u00e9e de lecture estim\u00e9e\" \/>\n\t<meta name=\"twitter:data2\" content=\"4 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/datascientest.com\/cle-primaire-tout-savoir\",\"url\":\"https:\/\/datascientest.com\/cle-primaire-tout-savoir\",\"name\":\"Cl\u00e9 primaire : D\u00e9finition, avantages et particularit\u00e9s\",\"isPartOf\":{\"@id\":\"https:\/\/datascientest.com\/#website\"},\"datePublished\":\"2023-06-13T07:30:00+00:00\",\"dateModified\":\"2023-11-09T13:52:06+00:00\",\"author\":{\"@id\":\"https:\/\/datascientest.com\/#\/schema\/person\/6eca16f63daaafcbc96e15549b9d4ee1\"},\"description\":\"Afin d\u2019identifier, sans \u00e9quivoque, les diff\u00e9rents enregistrements d\u2019une table, il y a les cl\u00e9s primaires. 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