{"id":1147,"date":"2024-07-31T11:29:47","date_gmt":"2024-07-31T09:29:47","guid":{"rendered":"https:\/\/blog.sutilweb.eu\/?page_id=1147"},"modified":"2024-07-31T11:29:47","modified_gmt":"2024-07-31T09:29:47","slug":"31-subconsultas","status":"publish","type":"page","link":"https:\/\/sutilweb.eu\/index.php\/databases\/sql\/31-subconsultas\/","title":{"rendered":"31. Subconsultas"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">Una <strong>subconsulta<\/strong> es una consulta dentro de otra. Por ejm, una consulta interesante ser\u00eda saber de las bandas de nuestra <strong>base de datos<\/strong>, cuantas bandas pertenecen a un estilo en concreto, o a un a\u00f1o en concreto, entonces podr\u00edamos hacer una consulta que nos trajera el conteo de cuantas bandas hay con ese estilo, de ese a\u00f1o&#8230;<\/p>\n\n\n\n<!--more-->\n\n\n\n<p class=\"wp-block-paragraph\">Veamos su sintaxis.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Ejm (n\u00famero de bandas que pertenecen a cada estilo)<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">SELECT estilo, (SELECT COUNT(*) FROM  bandas b WHERE e.estilo_id=b.estilo_id) AS total_bandas FROM estilos e;<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Se pueden hacer sub sub consultas a partir de una segunda consulta, pero ojo, se trata de consultas que demandan cierto procesamiento a la <strong>base de datos<\/strong>, la cual, si va teniendo miles o millones de campos, pueden ir ralentizando la <strong>base de datos<\/strong>.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Nota:<\/strong> a m\u00e1s complejidad de nuestra consulta, m\u00e1s va a tardar en ejecutarla en bases de datos grandes.<\/p>\n<\/blockquote>\n","protected":false},"excerpt":{"rendered":"<p>Una subconsulta es una consulta dentro de otra. Por ejm, una consulta interesante ser\u00eda saber de las bandas de nuestra base de&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1076,"menu_order":30,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_uag_custom_page_level_css":"","footnotes":""},"class_list":["post-1147","page","type-page","status-publish","hentry"],"uagb_featured_image_src":{"full":false,"thumbnail":false,"medium":false,"medium_large":false,"large":false,"1536x1536":false,"2048x2048":false},"uagb_author_info":{"display_name":"Sutil Web","author_link":"https:\/\/sutilweb.eu\/index.php\/author\/sutilweb\/"},"uagb_comment_info":0,"uagb_excerpt":"Una subconsulta es una consulta dentro de otra. Por ejm, una consulta interesante ser\u00eda saber de las bandas de nuestra base de...","_links":{"self":[{"href":"https:\/\/sutilweb.eu\/index.php\/wp-json\/wp\/v2\/pages\/1147","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sutilweb.eu\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sutilweb.eu\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sutilweb.eu\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/sutilweb.eu\/index.php\/wp-json\/wp\/v2\/comments?post=1147"}],"version-history":[{"count":1,"href":"https:\/\/sutilweb.eu\/index.php\/wp-json\/wp\/v2\/pages\/1147\/revisions"}],"predecessor-version":[{"id":1148,"href":"https:\/\/sutilweb.eu\/index.php\/wp-json\/wp\/v2\/pages\/1147\/revisions\/1148"}],"up":[{"embeddable":true,"href":"https:\/\/sutilweb.eu\/index.php\/wp-json\/wp\/v2\/pages\/1076"}],"wp:attachment":[{"href":"https:\/\/sutilweb.eu\/index.php\/wp-json\/wp\/v2\/media?parent=1147"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}