{"id":15,"date":"2018-02-06T09:46:59","date_gmt":"2018-02-06T09:46:59","guid":{"rendered":"http:\/\/mein-it-wissen.net\/?p=15"},"modified":"2018-02-06T09:46:59","modified_gmt":"2018-02-06T09:46:59","slug":"differenzen-bei-inner-join-vs-where-exists","status":"publish","type":"post","link":"https:\/\/mein-it-wissen.net\/?p=15","title":{"rendered":"Differenzen bei INNER JOIN vs. WHERE EXISTS"},"content":{"rendered":"<p>Normalerweise kann man davon ausgehen, dass ein WHERE EXISTS in einer SQL-Abfrage die gleiche Datenmenge zur\u00fcckliefert<\/p>\n<p>wie der entsprechende JOIN.<\/p>\n<p>Das funktioniert allerdings nur dann, wenn man f\u00fcr beide Varianten einen Schl\u00fcssel verwendet, der eindeutig ist.<\/p>\n<p>Ansonsten liefern beide unterschiedliche Anzahlen, welche unterschiedliche Duplikate enthalten k\u00f6nnen.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Normalerweise kann man davon ausgehen, dass ein WHERE EXISTS in einer SQL-Abfrage die gleiche Datenmenge zur\u00fcckliefert wie der entsprechende JOIN. Das funktioniert allerdings nur dann, wenn man f\u00fcr beide Varianten einen Schl\u00fcssel verwendet, der eindeutig &hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7,3],"tags":[],"class_list":["post-15","post","type-post","status-publish","format-standard","hentry","category-heute-gelernt","category-sql"],"_links":{"self":[{"href":"https:\/\/mein-it-wissen.net\/index.php?rest_route=\/wp\/v2\/posts\/15","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mein-it-wissen.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mein-it-wissen.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mein-it-wissen.net\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mein-it-wissen.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=15"}],"version-history":[{"count":1,"href":"https:\/\/mein-it-wissen.net\/index.php?rest_route=\/wp\/v2\/posts\/15\/revisions"}],"predecessor-version":[{"id":16,"href":"https:\/\/mein-it-wissen.net\/index.php?rest_route=\/wp\/v2\/posts\/15\/revisions\/16"}],"wp:attachment":[{"href":"https:\/\/mein-it-wissen.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=15"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mein-it-wissen.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=15"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mein-it-wissen.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=15"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}