{"id":625,"date":"2021-02-01T21:30:05","date_gmt":"2021-02-02T02:30:05","guid":{"rendered":"https:\/\/www.alpharithms.com\/?post_type=term&#038;p=625"},"modified":"2021-07-27T08:08:30","modified_gmt":"2021-07-27T12:08:30","slug":"data-definition-language","status":"publish","type":"post","link":"https:\/\/www.alpharithms.com\/data-definition-language-053021\/","title":{"rendered":"Data Definition Language"},"content":{"rendered":"<p>A data definition language (DDL) is a syntax provided by a database management system (DBMS) used to define the structure of data (schema) within a database. This type of language is used to create and modify object representations such as tables, indexes, and views.<\/p>\n<p>In structured query language (SQL) DDL commands are used to access, manipulate, and update data. Examples of these commands include <code class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\">CREATE<\/code>, <code class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\">DROP<\/code>, and <code class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\">DELETE<\/code>. As the syntax implies, the <code class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\">CREATE<\/code> command can be used to perform actions such as <code class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\">CREATE TABLE<\/code> or <code class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\">CREATE VIEW<\/code> based on programmer intent.<\/p>\n<p>Sequences of DDL commands are often preserved in scripts for common or repeated operations. For example, the <a href=\"https:\/\/www.alpharithms.com\/django-postgresql-install-tutorial-123816\/\">Django framework<\/a> provides a built-in database migration management system that auto-generates DDL to create or alter database schema based on its class-based modeling system.<\/p>\n<p>Data definition languages are\u00a0<em>very<\/em> similar to Data manipulation language (DML). In practice, these are the same root language and merely subsets of commands. For example, data definitions are made with the <code class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\">CREATE<\/code>, <code class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\">DELETE<\/code>, and <code class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\">DROP<\/code> commands whereas data manipulation language consists of <code class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\">UPDATE<\/code>, <code class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\">SELECT<\/code>, and <code class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\">INSERT<\/code>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>A data definition language (DDL) is a syntax provided by a database management system (DBMS) used to define the structure of data (schema) within a database. This type of language is used to create and modify object representations such as tables, indexes, and views. In structured query language (SQL) DDL commands are used to access, [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":628,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[260],"tags":[156,461],"acf":[],"_links":{"self":[{"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/posts\/625"}],"collection":[{"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/comments?post=625"}],"version-history":[{"count":1,"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/posts\/625\/revisions"}],"predecessor-version":[{"id":629,"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/posts\/625\/revisions\/629"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/media\/628"}],"wp:attachment":[{"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/media?parent=625"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/categories?post=625"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.alpharithms.com\/wp-json\/wp\/v2\/tags?post=625"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}