{"id":29231,"date":"2024-04-15T10:55:59","date_gmt":"2024-04-15T09:55:59","guid":{"rendered":"https:\/\/nelkodev.com\/blog\/domina-las-variables-definidas-por-el-usuario-en-mysql\/"},"modified":"2024-06-03T17:45:15","modified_gmt":"2024-06-03T16:45:15","slug":"domina-las-variables-definidas-por-el-usuario-en-mysql","status":"publish","type":"post","link":"https:\/\/nelkodev.com\/en\/blog\/master-user-defined-variables-in-mysql\/","title":{"rendered":"Master User Defined Variables in MySQL"},"content":{"rendered":"<p>User-defined variables in MySQL offer a flexible and powerful way to manipulate data during the execution of SQL statements. These variables are especially useful in complex scripts, where you need to store temporary results, manipulate values during multiple calculation steps, or simply to simplify complex queries by reusing values. This article provides a detailed guide on how to take advantage of these variables to improve and simplify your interactions with MySQL databases.<\/p>\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_80 counter-hierarchy ez-toc-counter ez-toc-custom ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #ffffff;color:#ffffff\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewbox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #ffffff;color:#ffffff\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewbox=\"0 0 24 24\" version=\"1.2\" baseprofile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/nelkodev.com\/en\/blog\/master-user-defined-variables-in-mysql\/#%C2%BFQue_Son_las_Variables_Definidas_por_el_Usuario\" >What Are User Defined Variables?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/nelkodev.com\/en\/blog\/master-user-defined-variables-in-mysql\/#Declaracion_y_Configuracion\" >Declaration and Configuration<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/nelkodev.com\/en\/blog\/master-user-defined-variables-in-mysql\/#Operaciones_con_Variables\" >Operations with Variables<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/nelkodev.com\/en\/blog\/master-user-defined-variables-in-mysql\/#Ventajas_de_Usar_Variables_Definidas_por_el_Usuario\" >Advantages of Using User Defined Variables<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/nelkodev.com\/en\/blog\/master-user-defined-variables-in-mysql\/#Flexibilidad\" >Flexibility<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/nelkodev.com\/en\/blog\/master-user-defined-variables-in-mysql\/#Reduccion_de_la_Redundancia\" >Redundancy Reduction<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/nelkodev.com\/en\/blog\/master-user-defined-variables-in-mysql\/#Mejora_en_el_Rendimiento\" >Improved Performance<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/nelkodev.com\/en\/blog\/master-user-defined-variables-in-mysql\/#Consideraciones_y_Buenas_Practicas\" >Considerations and Good Practices<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/nelkodev.com\/en\/blog\/master-user-defined-variables-in-mysql\/#Alcance_y_Persistencia\" >Reach and Persistence<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/nelkodev.com\/en\/blog\/master-user-defined-variables-in-mysql\/#Nombres_Descriptivos\" >Descriptive Names<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/nelkodev.com\/en\/blog\/master-user-defined-variables-in-mysql\/#Precauciones_de_Seguridad\" >Safety precautions<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/nelkodev.com\/en\/blog\/master-user-defined-variables-in-mysql\/#Conclusion\" >Conclusion<\/a><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"%C2%BFQue_Son_las_Variables_Definidas_por_el_Usuario\"><\/span>What Are User Defined Variables?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>User-defined variables in MySQL are objects that store a value that can be used and modified within a MySQL session. These variables exist only during the current connection and are lost once the session is closed. They can be used to store any type of data supported by MySQL, including numbers, strings, and dates.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Declaracion_y_Configuracion\"><\/span>Declaration and Configuration<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Creating a user-defined variable is surprisingly simple. You use the symbol <code>@<\/code> followed by the name you want to assign to the variable. For example:<\/p>\n<pre><code class=\"&quot;language-sql&quot;\">SET @myVariable = 10;<\/code><\/pre>\n<p>This command will assign the value 10 to <code>@myVariable<\/code>. You can also assign values to variables directly with an SQL query:<\/p>\n<pre><code class=\"&quot;language-sql&quot;\">SELECT @myNumber := COUNT(*) FROM users;<\/code><\/pre>\n<p>Here, <code>@my number<\/code> will store the total number of users in the table <code>users<\/code>.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Operaciones_con_Variables\"><\/span>Operations with Variables<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Once you&#039;ve defined a variable, you can use it almost anywhere in your SQL statements that accept literal values. For example:<\/p>\n<pre><code class=\"&quot;language-sql&quot;\">SELECT name, age FROM employees WHERE age &gt; @myVariable;<\/code><\/pre>\n<p>This usage simplifies writing dynamic queries where values can change based on the results of previous operations or applied business logic.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Ventajas_de_Usar_Variables_Definidas_por_el_Usuario\"><\/span>Advantages of Using User Defined Variables<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><span class=\"ez-toc-section\" id=\"Flexibilidad\"><\/span>Flexibility<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>You can modify the value of a user-defined variable at any point in the session, giving you tremendous flexibility to control the flow of SQL operations in your scripts or applications.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Reduccion_de_la_Redundancia\"><\/span>Redundancy Reduction<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Avoid repetition of complicated queries and improve code clarity. Instead of replicating a complicated subquery multiple times, you can run it once, store the result in a variable, and reference that variable elsewhere in the script.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Mejora_en_el_Rendimiento\"><\/span>Improved Performance<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Although the benefit may vary, in some cases, using variables to store intermediate results can reduce database access time and improve the overall performance of your queries.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Consideraciones_y_Buenas_Practicas\"><\/span>Considerations and Good Practices<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><span class=\"ez-toc-section\" id=\"Alcance_y_Persistencia\"><\/span>Reach and Persistence<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Remember that these variables only have scope within the current session in which they are created. If you need long-term or session-to-session persistence, you should consider alternatives such as temporary tables or storage in your client application.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Nombres_Descriptivos\"><\/span>Descriptive Names<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>To improve the readability and maintainability of your code, use descriptive names for your variables. For example, instead of <code>@to<\/code>, uses <code>@contadorUsuarios<\/code> for a variable that counts users.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Precauciones_de_Seguridad\"><\/span>Safety precautions<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Use caution when using dynamic data within your variables to avoid SQL injections. Always validate and clean the data when the variables act as intermediaries for user input or when their content is manipulated by the user.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Conclusion\"><\/span>Conclusion<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>User-defined variables in MySQL are powerful tools that, when used properly, can make a big difference in the efficiency and clarity of your databases and SQL scripts. With the practices and examples provided here, you are well equipped to start using these variables in your projects. Remember to always consult the <a href=\"https:\/\/dev.mysql.com\/doc\/\" rel=\"nofollow noopener\" target=\"_blank\">official MySQL documentation<\/a> for additional details and to stay up to date with best practices.<\/p>\n<p>For any questions or queries, do not hesitate to visit <a href=\"https:\/\/nelkodev.com\/en\/contact\/\">my contact page<\/a>. I&#039;m here to help you on your path to MySQL mastery!<\/p>","protected":false},"excerpt":{"rendered":"<p>Las variables definidas por el usuario en MySQL ofrecen una forma flexible y potente de manipular datos durante la ejecuci\u00f3n de las declaraciones SQL. Estas variables son especialmente \u00fatiles en scripts complejos, donde se requiere almacenar resultados temporales, manipular valores durante m\u00faltiples pasos de c\u00e1lculo o simplemente para simplificar queries complejas reutilizando valores. Este art\u00edculo [&hellip;]<\/p>","protected":false},"author":1,"featured_media":29232,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[420,2185],"tags":[41,9,205,2013,2189,2059,1473,2200,624,48,352,372,791],"class_list":["post-29231","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog","category-curso-mysql","tag-por","tag-base-de-datos","tag-blog","tag-csv","tag-curso","tag-definidas","tag-domina","tag-export","tag-import","tag-las","tag-mysql","tag-usuario","tag-variables"],"_links":{"self":[{"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/posts\/29231","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/comments?post=29231"}],"version-history":[{"count":0,"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/posts\/29231\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/media\/29232"}],"wp:attachment":[{"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/media?parent=29231"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/categories?post=29231"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/tags?post=29231"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}