{"id":1149,"date":"2024-07-31T11:30:36","date_gmt":"2024-07-31T09:30:36","guid":{"rendered":"https:\/\/blog.sutilweb.eu\/?page_id=1149"},"modified":"2024-07-31T11:30:36","modified_gmt":"2024-07-31T09:30:36","slug":"32-vistas","status":"publish","type":"page","link":"https:\/\/sutilweb.eu\/index.php\/databases\/sql\/32-vistas\/","title":{"rendered":"32. Vistas"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">En <strong>SQL,<\/strong> una <strong>vista<\/strong> es una <strong>tabla virtual<\/strong> que deriva de una o varias <strong>tablas<\/strong> existentes de la misma. No almacena f\u00edsicamente los datos, se trata de una consulta predefinida o preexistente en nuestra <strong>base de datos<\/strong>, que cuando queramos acceder a ella se va a ejecutar.<\/p>\n\n\n\n<!--more-->\n\n\n\n<p class=\"wp-block-paragraph\">La sintaxis de la vista es la siguiente.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Ejm<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">-- Creamos una vista\nCREATE VIEW vista_bandas AS \nSELECT * FROM bandas\nWHERE nombre='Metallica';\n\n-- Seleccionamos la vista para visualizarla\nSELECT * FROM vista_bandas;\n\n-- Eliminar una vista\nDROP VIEW vista_bandas;\n\n-- Visualizar todas las vistas de la base de datos\nSHOW FULL TABLES IN musica (base de datos) WHERE TABLE_TYPE LIKE 'VIEW'\n<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Una vez definida, puede ser tratada como otra <strong>tabla de la base de datos<\/strong>, permitiendo que se realicen consultas de actualizaci\u00f3n y eliminaci\u00f3n de registros, aunque, si no tenemos un buen control o conocimiento de la l\u00f3gica de nuestra <strong>base de datos<\/strong>, es mejor no tratar de hacer deletes o updates mediante las <strong>vistas,<\/strong> si no simplemente lecturas de datos a la misma mediante lo que se denomina una <strong>transacci\u00f3n<\/strong>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Utilidad de las vistas<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Las <strong>vistas<\/strong> van a proporcionar una capa adicional de abstracci\u00f3n. Pensemos por ejm en usuarios de nivel medio, que no necesitan conocer todos los detalles que se almacenen en la <strong>bases de datos<\/strong>, y s\u00f3lo necesiten cierta parte para trabajar. Se puede construir una <strong>vista<\/strong> para este tipo de perfiles, los cuales puedan trabajar con ellas sin necesidad de conocer el resto de informaci\u00f3n de la <strong>base de datos<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Tambi\u00e9n pueden servir para simplificar consultas m\u00e1s complejas, ya que pueden contener consultas m\u00e1s elaboradas dentro de otras, y por ende, las podemos utilizar como una tabla.<\/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> las <strong>vistas<\/strong> son muy \u00fatiles para aquellas personas que manejan la base de datos sin ser administradores.<\/p>\n<\/blockquote>\n","protected":false},"excerpt":{"rendered":"<p>En SQL, una vista es una tabla virtual que deriva de una o varias tablas existentes de la misma. No [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1076,"menu_order":31,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_uag_custom_page_level_css":"","site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","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":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","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":"var(--ast-global-color-4)","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":""},"class_list":["post-1149","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":"En SQL, una vista es una tabla virtual que deriva de una o varias tablas existentes de la misma. No [&hellip;]","_links":{"self":[{"href":"https:\/\/sutilweb.eu\/index.php\/wp-json\/wp\/v2\/pages\/1149","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=1149"}],"version-history":[{"count":1,"href":"https:\/\/sutilweb.eu\/index.php\/wp-json\/wp\/v2\/pages\/1149\/revisions"}],"predecessor-version":[{"id":1150,"href":"https:\/\/sutilweb.eu\/index.php\/wp-json\/wp\/v2\/pages\/1149\/revisions\/1150"}],"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=1149"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}