Editing SQL (section)

{{Short description|Relational database programming language}}
{{use dmy dates|date=December 2024}}
{{Use American English|date=March 2025}}
{{About|the database language}}
{{redirect|SEQUEL|the topic of the word|sequel|other uses|Sequel (disambiguation)}}
{{infobox programming language
| name = SQL (Structured Query Language)
| paradigm = [[Declarative programming|Declarative]]
| family = [[Query language]]
| released = {{Start date and age|1973|df=yes}}
| designer = [[Donald D. Chamberlin]]<br />[[Raymond F. Boyce]]
| developer = [[ISO/IEC JTC 1/SC 32|ISO/IEC JTC&nbsp;1 (Joint Technical Committee&nbsp;1) / SC&nbsp;32 (Subcommittee&nbsp;32)]] / WG&nbsp;3 (Working Group&nbsp;3)
| typing = [[Static typing|Static]], [[Strong typing|strong]]
| implementations = [[List of relational database management systems|Many]]
| dialects = {{flatlist|
* SQL-86
* SQL-89
* [[SQL-92]]
* [[SQL:1999]]
* [[SQL:2003]]
* [[SQL:2006]]
* [[SQL:2008]]
* [[SQL:2011]]
* [[SQL:2016]]
* [[SQL:2023]]
}}
| influenced = [[Contextual Query Language|CQL]], [[Language Integrated Query|LINQ]], [[SPARQL]], SOQL, [[PowerShell]],<ref name="ars" /> [[Java Persistence Query Language|JPQL]], [[Java Object Oriented Querying|jOOQ]], [[N1QL]], [[Graph Query Language|GQL]]
| website = {{URL|https://www.iso.org/standard/76583.html}}
| latest_release_version = [[SQL:2023]]
| latest_release_date = {{Start date and age|2023|06|df=yes}}
| influenced_by = [[Datalog]]
| operating_system = [[Cross-platform]]
| fileformat = 
| wikibooks = Structured Query Language
}}
{{Infobox file format
| name          = SQL (file format)
| icon          = 
| extension     = .sql
| mime          = application/sql<ref name="iana" /><ref name="application/sql" />
| uniform type  = 
| owner         = [[ISO]]/[[International Electrotechnical Commission|IEC]]
| released      = {{Start date and age|1986|df=yes}}
| latest release version = 
| latest release date = 
| genre         = Database
| standard      = [[ISO/IEC 9075]]
| open          = Yes
| url           = {{URL|https://www.iso.org/standard/76583.html}}
}}

'''Structured Query Language''' ('''SQL''') (<small>pronounced</small> {{IPAc-en|ˌ|ɛ|s|ˌ|k|j|u|ˈ|ɛ|l}} ''S-Q-L''; <small>or alternatively as</small> {{IPAc-en|ˈ|s|iː|k|w|ə|l|audio=LL-Q1860 (eng)-Flame, not lame-SQL.wav}} "sequel")
<ref name="learningSQL" /><ref name="chamberlin2001">{{cite journal |url=https://conservancy.umn.edu/handle/11299/107215 |last1=Chamberlin |first1=Donald D. |first2=Philip L. |last2=Frana |website=University Digital Conservancy |title=Oral history interview with Donald D. Chamberlin |date=3 October 2001 |hdl=11299/107215 |access-date=14 January 2020 |quote=We changed the original name "SEQUEL" to SQL because we got a letter from somebody's lawyer that said the name "SEQUEL" belonged to them. We shortened it to SQL, for Structured Query Language, and the product was known as SQL/DS. |archive-date=24 February 2020 |archive-url=https://web.archive.org/web/20200224145836/https://conservancy.umn.edu/handle/11299/107215 |url-status=live }}</ref> is a [[domain-specific language]] used to manage data, especially in a [[relational database management system]] (RDBMS). It is particularly useful in handling [[Data model|structured data]], i.e., data incorporating relations among entities and variables.

Introduced in the 1970s, SQL offered two main advantages over older read&ndash;write [[API]]s such as [[ISAM]] or [[VSAM]]. Firstly, it introduced the concept of accessing many [[Record (computer science)|records]] with one single [[Command-line interface|command]]. Secondly, it eliminates the need to specify ''how'' to reach a record, i.e., with or without an [[Database index|index]].

Originally based upon [[relational algebra]] and [[tuple relational calculus]], SQL consists of many types of statements,<ref>[[SQL-92]], 4.22 SQL-statements, 4.22.1 Classes of SQL-statements "There are at least five ways of classifying SQL-statements:", 4.22.2, SQL statements classified by function "The following are the main classes of SQL-statements:"; [[SQL:2003]] 4.11 SQL-statements, and later revisions.</ref> which may be informally classed as [[sublanguage]]s, commonly: [[Data Query language|Data query Language]] (DQL), [[data definition language|Data Definition Language]] (DDL), [[data control language|Data Control Language]] (DCL), and [[data manipulation language|Data Manipulation Language]] (DML).<ref>{{cite book
|title=Structured Query Language By Example - Volume I: Data Query Language
|first=Mark
|last=Chatham
|url=https://books.google.com/books?id=64MBBAAAQBAJ&pg=PA8
|year=2012
|isbn=9781291199512
|page=8
|publisher=Lulu.com
}}</ref>

The scope of SQL includes data query, data manipulation (insert, update, and delete), data definition ([[database schema|schema]] creation and modification), and data access control. Although SQL is essentially a [[Declarative programming|declarative language]] ([[4GL]]), it also includes [[Procedural programming|procedural]] elements.

SQL was one of the first commercial languages to use [[Edgar F. Codd]]'s [[relational model]]. The model was described in his influential 1970 paper, "A Relational Model of Data for Large Shared Data Banks".<ref name="codd-relational-model" />  Despite not entirely adhering to [[Codd's 12 rules|the relational model as described by Codd]], SQL became the most widely used database language.<ref name="SQL-Fundamentals" /><ref name="IBM-sql" />

SQL became a [[Technical standard|standard]] of the [[American National Standards Institute]] (ANSI) in 1986 and of the [[International Organization for Standardization]] (ISO) in 1987.<ref name="ISO 9075:1987" /> Since then, the standard has been revised multiple times to include a larger set of features and incorporate common extensions. Despite the existence of standards, virtually no implementations in existence adhere to it fully, and most SQL code requires at least some changes before being ported to different [[database]] systems.
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