{"id":126,"date":"2019-03-20T21:01:03","date_gmt":"2019-03-20T21:01:03","guid":{"rendered":"https:\/\/math-brownies.de\/?p=126"},"modified":"2019-03-20T21:01:48","modified_gmt":"2019-03-20T21:01:48","slug":"mysql-datenbanken-auslesen","status":"publish","type":"post","link":"https:\/\/math-brownies.de\/index.php\/2019\/03\/20\/mysql-datenbanken-auslesen\/","title":{"rendered":"MYSQL Datenbanken auslesen"},"content":{"rendered":"\n<p>F\u00fcr das Projekt eines Sch\u00fclers standen wir heute vor dem Problem, Daten aus der Mysql-Datenbank auslesen zu wollen, die \u00fcber eine Realtionstabelle verkn\u00fcpft waren. Konkret war das ERM so:<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"684\" height=\"181\" src=\"https:\/\/math-brownies.de\/wp-content\/uploads\/2019\/03\/erm-einkaufsliste.png\" alt=\"\" class=\"wp-image-127\" srcset=\"https:\/\/math-brownies.de\/wp-content\/uploads\/2019\/03\/erm-einkaufsliste.png 684w, https:\/\/math-brownies.de\/wp-content\/uploads\/2019\/03\/erm-einkaufsliste-300x79.png 300w\" sizes=\"auto, (max-width: 684px) 100vw, 684px\" \/><\/figure>\n\n\n\n<p>Nun wollten wir alle Artikel einer Liste eines Users auslesen. Also alle Artikel, die in der Realtionstabelle zu einer festgelegten Listenid genannt werden. \u00dcbereinstimmen muss als die Listenid (in unserem Beispiel die Liste mit der id 1) und die Artikelid (in der Relationstabelle und in der Artikeltabelle).<\/p>\n\n\n\n<p>Es gibt zwei Arten, dies zu realisieren. Die \u00fcbliche Art w\u00e4re der Befehl &#8222;join&#8220;:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\"><p>SELECT artikel.name, artikel. preis FROM artikel LEFT JOIN rel ON  rel.ida=artikel.ida WHERE rel.idl=1<\/p><p><\/p><\/blockquote>\n\n\n\n<p>Heute abend habe ich gelernt, das es aber auch nur mit den Befehlen SELECT, FROM und WHERE ginge, wenn man logische Verkn\u00fcpfungen nutzt:<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\"><p> <code><a href=\"https:\/\/phpmyadmin.gitola.de\/url.php?url=http:\/\/dev.mysql.com\/doc\/refman\/5.5\/en\/select.html\">SELECT<\/a> artikel.name, artikel.preis FROM artikel, liste, relationstabelle WHERE   liste.ID_l=1 <a href=\"https:\/\/phpmyadmin.gitola.de\/url.php?url=http:\/\/dev.mysql.com\/doc\/refman\/5.5\/en\/logical-operators.html#operator_and\">AND<\/a> relationstabelle.ID_a=artikel.ID_a <\/code><\/p><\/blockquote>\n\n\n\n<p>Das geht sogar auch denn, wenn man noch mehr Bedingungen und Tabellen hinzuf\u00fcgt &#8211; erg\u00e4nzt man zum Beispiel die Tabelle Benutzer und listet die Bedingungen &#8222;<code>WHERE  liste.ID_b=1 <a href=\"https:\/\/phpmyadmin.gitola.de\/url.php?url=http:\/\/dev.mysql.com\/doc\/refman\/5.5\/en\/logical-operators.html#operator_and\">AND<\/a> liste.ID_l=relationstabelle.ID_l <a href=\"https:\/\/phpmyadmin.gitola.de\/url.php?url=http:\/\/dev.mysql.com\/doc\/refman\/5.5\/en\/logical-operators.html#operator_and\">AND<\/a> relationstabelle.ID_a=artikel.ID_a\",<\/code>so bekommt man alle Artikel eines Users &#8211; sie werden doppelt gelistet, wenn sie auf verschiedenen Listen doppelt stehen. <\/p>\n","protected":false},"excerpt":{"rendered":"<p>F\u00fcr das Projekt eines Sch\u00fclers standen wir heute vor dem Problem, Daten aus der Mysql-Datenbank auslesen zu wollen, die \u00fcber eine Realtionstabelle verkn\u00fcpft waren. Konkret war das ERM so: Nun wollten wir alle Artikel einer Liste eines Users auslesen. Also alle Artikel, die in der Realtionstabelle zu einer festgelegten Listenid genannt werden. \u00dcbereinstimmen muss als [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"default","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"default","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[4,3],"tags":[29,27,28],"class_list":["post-126","post","type-post","status-publish","format-standard","hentry","category-datenbanken","category-informatik","tag-datenbanken","tag-join","tag-verknuepfungen"],"_links":{"self":[{"href":"https:\/\/math-brownies.de\/index.php\/wp-json\/wp\/v2\/posts\/126","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/math-brownies.de\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/math-brownies.de\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/math-brownies.de\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/math-brownies.de\/index.php\/wp-json\/wp\/v2\/comments?post=126"}],"version-history":[{"count":1,"href":"https:\/\/math-brownies.de\/index.php\/wp-json\/wp\/v2\/posts\/126\/revisions"}],"predecessor-version":[{"id":128,"href":"https:\/\/math-brownies.de\/index.php\/wp-json\/wp\/v2\/posts\/126\/revisions\/128"}],"wp:attachment":[{"href":"https:\/\/math-brownies.de\/index.php\/wp-json\/wp\/v2\/media?parent=126"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/math-brownies.de\/index.php\/wp-json\/wp\/v2\/categories?post=126"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/math-brownies.de\/index.php\/wp-json\/wp\/v2\/tags?post=126"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}