{"id":303,"date":"2018-12-13T08:22:06","date_gmt":"2018-12-13T08:22:06","guid":{"rendered":"https:\/\/barkhane.com\/sql\/2018\/12\/13\/sql-unique-key\/"},"modified":"2024-03-03T17:52:52","modified_gmt":"2024-03-03T17:52:52","slug":"sql-unique-key","status":"publish","type":"post","link":"https:\/\/barkhane.com\/sql\/sql-unique-key\/","title":{"rendered":"SQL Unique Key"},"content":{"rendered":"<p>A sql unique key is a set of one or more than one fields\/columns of a <a href=\"https:\/\/barkhane.com\/sql\/sql-table\/\">table<\/a> that uniquely identify a record in a database table.<\/p>\n<p>You can say that it is little like primary key but it can accept only one null value and it cannot have duplicate values.<\/p>\n<p>The unique key and primary key both provide a guarantee for uniqueness for a column or a set of columns.<\/p>\n<p>There is an automatically defined unique key constraint within a primary key constraint.<\/p>\n<p>There may be many sql unique key constraints for one table, but only one <a href=\"https:\/\/barkhane.com\/sql\/sql-primary-key\/\">PRIMARY KEY<\/a> constraint for one table.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>A sql unique key is a set of one or more than one fields\/columns of a table that uniquely identify [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"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 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