{"id":29049,"date":"2024-04-29T10:56:27","date_gmt":"2024-04-29T09:56:27","guid":{"rendered":"https:\/\/nelkodev.com\/blog\/domina-las-consultas-sql-aprende-a-usar-select-from\/"},"modified":"2024-06-03T17:44:06","modified_gmt":"2024-06-03T16:44:06","slug":"domina-las-consultas-sql-aprende-a-usar-select-from","status":"publish","type":"post","link":"https:\/\/nelkodev.com\/en\/blog\/master-sql-queries-learn-to-use-select-from\/","title":{"rendered":"Master SQL Queries: Learn to Use SELECT FROM"},"content":{"rendered":"<p>When it comes to managing information in databases, one of the most crucial and fundamental aspects is to perform effective queries that allow you to obtain exactly the data you need. SQL, the structured query language, is the indispensable tool in the arsenal of any developer, data analyst, or database administrator. Today we are going to focus on one of the most basic and essential operations in SQL: the use of <code>SELECT FROM<\/code>.<\/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-sql-queries-learn-to-use-select-from\/#%C2%BFQue_es_SQL_y_por_que_es_importante\" >What is SQL and why is it important?<\/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-sql-queries-learn-to-use-select-from\/#Entendiendo_la_estructura_basica_de_una_consulta_SQL\" >Understanding the basic structure of a SQL query<\/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-sql-queries-learn-to-use-select-from\/#Ejemplos_Practicos_de_Uso_de_SELECT_FROM\" >Practical Examples of Using SELECT FROM<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/nelkodev.com\/en\/blog\/master-sql-queries-learn-to-use-select-from\/#Consulta_Basica_Seleccionar_Todos_los_Datos_de_una_Tabla\" >Basic Query: Select All Data from a Table<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/nelkodev.com\/en\/blog\/master-sql-queries-learn-to-use-select-from\/#Seleccionando_Columnas_Especificas\" >Selecting Specific Columns<\/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-sql-queries-learn-to-use-select-from\/#Uso_de_WHERE_para_Filtrar_Datos\" >Using WHERE to Filter Data<\/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-sql-queries-learn-to-use-select-from\/#Combinando_Condiciones\" >Combining Conditions<\/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-sql-queries-learn-to-use-select-from\/#Mejores_Practicas_y_Consideraciones\" >Best Practices and Considerations<\/a><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"%C2%BFQue_es_SQL_y_por_que_es_importante\"><\/span>What is SQL and why is it important?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>SQL (Structured Query Language) is a language designed specifically to manage and manipulate relational databases. Through SQL, you can perform a variety of operations such as inserting, updating, deleting, and of course querying data from a database. Its ease of use and powerful ability to handle large data sets make it a de facto standard in database manipulation.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Entendiendo_la_estructura_basica_de_una_consulta_SQL\"><\/span>Understanding the basic structure of a SQL query<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>A basic SQL query using <code>SELECT FROM<\/code> has the following structure:<\/p>\n<pre><code class=\"&quot;language-sql&quot;\">SELECT column1, column2 FROM table_name WHERE condition<\/code><\/pre>\n<ul>\n<li><strong>SELECT<\/strong>: Here you specify the columns you want to retrieve from the database.<\/li>\n<li><strong>DESDE<\/strong>: Here you specify the table from which you want to retrieve data.<\/li>\n<li><strong>WHERE<\/strong>: This is optional and is used to filter the records based on certain conditions.<\/li>\n<\/ul>\n<h2><span class=\"ez-toc-section\" id=\"Ejemplos_Practicos_de_Uso_de_SELECT_FROM\"><\/span>Practical Examples of Using SELECT FROM<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>To illustrate how to use <code>SELECT FROM<\/code>, we will consider an example database that contains a table called <code>Employees<\/code>. This table includes columns like <code>ID<\/code>, <code>Name<\/code>, <code>Post<\/code>, and <code>Salary<\/code>.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Consulta_Basica_Seleccionar_Todos_los_Datos_de_una_Tabla\"><\/span>Basic Query: Select All Data from a Table<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>If you need to get a list of all employees along with all their information, your SQL query would be the following:<\/p>\n<pre><code class=\"&quot;language-sql&quot;\">SELECT * FROM Employees<\/code><\/pre>\n<p>Here, the asterisk (<code>*<\/code>) indicates that you want to select all columns in the table <code>Employees<\/code>.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Seleccionando_Columnas_Especificas\"><\/span>Selecting Specific Columns<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Let&#039;s say you&#039;re only interested in seeing the name and title of each employee. Then you would modify the query like this:<\/p>\n<pre><code class=\"&quot;language-sql&quot;\">SELECT Name, Position FROM Employees<\/code><\/pre>\n<h3><span class=\"ez-toc-section\" id=\"Uso_de_WHERE_para_Filtrar_Datos\"><\/span>Using WHERE to Filter Data<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Let&#039;s say you want to find the information of employees who earn more than $3,000. Your query would include a clause <code>WHERE<\/code>:<\/p>\n<pre><code class=\"&quot;language-sql&quot;\">SELECT * FROM Employees WHERE Salary &gt; 3000<\/code><\/pre>\n<h3><span class=\"ez-toc-section\" id=\"Combinando_Condiciones\"><\/span>Combining Conditions<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>You can also combine multiple conditions using operators like <code>AND<\/code> y <code>OR<\/code>. For example, if you wanted to find employees with the title &quot;Manager&quot; who make more than $5,000, you would use:<\/p>\n<pre><code class=\"&quot;language-sql&quot;\">SELECT * FROM Employees WHERE Position = &#039;Manager&#039; AND Salary &gt; 5000<\/code><\/pre>\n<h2><span class=\"ez-toc-section\" id=\"Mejores_Practicas_y_Consideraciones\"><\/span>Best Practices and Considerations<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>When writing SQL queries with <code>SELECT FROM<\/code>, it is important to follow some best practices to ensure that your queries are efficient, secure, and easy to maintain:<\/p>\n<ol>\n<li>\n<p>*<em>Avoid Using `SELECT <\/em>` in Production**: Although convenient for quick testing, in a production environment it is better to specify the columns you actually need. This not only improves performance, but also makes your code cleaner and more maintainable.<\/p>\n<\/li>\n<li>\n<p><strong>Use Aliases to Improve Readability<\/strong>: If your tables or columns have long or unclear names, you can use aliases to simplify your queries and make them more readable.<\/p>\n<\/li>\n<li>\n<p><strong>Maintain Consistency in Formulating Queries<\/strong>: Establish and follow formulation and formatting standards for all your SQL queries. This is especially useful when you work in a team.<\/p>\n<\/li>\n<li>\n<p><strong>Be Careful with Sensitive Data<\/strong>: When working with sensitive data, be sure to implement appropriate security measures, such as using parameterized queries to prevent SQL injection.<\/p>\n<\/li>\n<\/ol>\n<p>In conclusion, master <code>SELECT FROM<\/code> It&#039;s just the beginning of what you can do with SQL, but it&#039;s a fundamental and powerful step in any journey into the world of databases. I hope this tutorial helps you feel more comfortable and competent performing your own queries. And remember, you can always delve deeper into these topics with additional resources at <a href=\"https:\/\/nelkodev.com\/en\/\">https:\/\/nelkodev.com<\/a> or even contact me directly at <a href=\"https:\/\/nelkodev.com\/en\/contact\/\">https:\/\/nelkodev.com\/contacto<\/a> if you have questions or need personalized advice. Happy consultation!<\/p>","protected":false},"excerpt":{"rendered":"<p>When it comes to managing information in databases, one of the most crucial and fundamental aspects is to perform effective queries that allow you to obtain exactly the data you need. SQL, the structured query language, is the indispensable tool in the arsenal of any developer, data analyst or database administrator.<\/p>","protected":false},"author":1,"featured_media":29050,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[420,2044],"tags":[486,2195,205,1516,1473,2119,48,935,504,79],"class_list":["post-29049","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog","category-sql-basics","tag-aprende","tag-basics","tag-blog","tag-consultas","tag-domina","tag-from","tag-las","tag-select","tag-sql","tag-usar"],"_links":{"self":[{"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/posts\/29049","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=29049"}],"version-history":[{"count":0,"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/posts\/29049\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/media\/29050"}],"wp:attachment":[{"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/media?parent=29049"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/categories?post=29049"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nelkodev.com\/en\/wp-json\/wp\/v2\/tags?post=29049"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}