{"id":1145,"date":"2024-07-31T11:28:58","date_gmt":"2024-07-31T09:28:58","guid":{"rendered":"https:\/\/blog.sutilweb.eu\/?page_id=1145"},"modified":"2024-07-31T11:28:58","modified_gmt":"2024-07-31T09:28:58","slug":"30-refactorizando-bd-para-joins","status":"publish","type":"page","link":"https:\/\/sutilweb.eu\/index.php\/databases\/sql\/30-refactorizando-bd-para-joins\/","title":{"rendered":"30. Refactorizando BD para JOINS"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">En este cap\u00edtulo vamos a ver ejm de <strong>JOINS<\/strong> para entender su funcionamiento. Veamos una primera sintaxis.<\/p>\n\n\n\n<!--more-->\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Ejm LEFT JOIN<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">-- Uni\u00f3n a la izquierda con LEFT JOIN(Creamos Alias)\nSELECT * FROM bandas b\nLEFT JOIN estilos e\nON b.id_estilo=e.id_estilo;<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>&nbsp;Ejm RIGHT JOIN<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">-- Uni\u00f3n a la derecha con RIGH JOIN(Creamos Alias)\nSELECT * FROM bandas b\nRIGHT JOIN estilos e\nON b.id_estilo=e.id_estilo;<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Ejm INNER JOIN<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">-- Uni\u00f3n con INNER JOIN (Creamos Alias)\nSELECT * FROM bandas b\nINNER JOIN estilos e\nON b.id_estilo=e.id_estilo;<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Ejm FULL JOIN<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">-- Uni\u00f3n con FULL JOIN(Creamos Alias)\n-- Esta sentencia no la admiten todos los gestores de bases de datos\nSELECT * FROM bandas b\nFULL JOIN estilos e\nON b.id_estilo=e.id_estilo;<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Ejm 2 FULL JOIN<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">-- Uni\u00f3n a la izquierda con RIGH JOIN(Creamos Alias)\nSELECT * FROM bandas b\nLEFT JOIN estilos e\nON b.id_estilo=e.id_estilo;\nunion\n-- Uni\u00f3n a la derecha con RIGH JOIN(Creamos Alias) \nSELECT * FROM bandas b\n LEFT JOIN estilos e\n ON b.id_estilo=e.id_estilo;<\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">Dependiendo de las necesidades de nuestra l\u00f3gica de negocio, podemos utilizar cla\u00fasulas <strong><em>WHERE,<\/em> <em>GROUP BY<\/em><\/strong>. Veamos algunos ejms.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Ejm<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">SELECT b.nombre, e.estilo, b.bio\nFROM bandas a\nINNER JOIN estilos e\nON b.estilo_id=e.estilo_id\nWHERE e.estilo_id=0;<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>En este cap\u00edtulo vamos a ver ejm de JOINS para entender su funcionamiento. Veamos una primera sintaxis.<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1076,"menu_order":29,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_uag_custom_page_level_css":"","footnotes":""},"class_list":["post-1145","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 este cap\u00edtulo vamos a ver ejm de JOINS para entender su funcionamiento. Veamos una primera sintaxis.","_links":{"self":[{"href":"https:\/\/sutilweb.eu\/index.php\/wp-json\/wp\/v2\/pages\/1145","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=1145"}],"version-history":[{"count":1,"href":"https:\/\/sutilweb.eu\/index.php\/wp-json\/wp\/v2\/pages\/1145\/revisions"}],"predecessor-version":[{"id":1146,"href":"https:\/\/sutilweb.eu\/index.php\/wp-json\/wp\/v2\/pages\/1145\/revisions\/1146"}],"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=1145"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}