SQL

SQL
Paradigm Multi-paradigm: declarative
Family Programming language
Designed by Donald D. Chamberlin
Raymond F. Boyce
Developer ISO/IEC
First appeared 1974 (1974)
Typing discipline Static, strong
OS Cross-platform
File formats File format details
Filename extension .sql
Internet media type application/sql[1][2]
Developed by ISO/IEC
Initial release 1986 (1986)
Latest release
SQL:2016
(December 2016 (2016-12))
Type of format Database
Standard ISO/IEC 9075
Open format? Yes
Major implementations
Many
Dialects
Influenced by
Datalog
Influenced
CQL, LINQ, SOQL, PowerShell,[3] JPQL, jOOQ, N1QL

SQL (/ˌɛs.kjuːˈɛl/ ESS-kew-EL[4] or /ˈsiːkwəl/ SEE-kwəl,[5] Structured Query Language[6][7][8][9]) is a domain-specific language used in programming and designed for managing data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS). In comparison to older read/write APIs like ISAM or VSAM, SQL offers two main advantages: First, it introduced the concept of accessing many records with one single command, and second, it eliminates the need to specify how to reach a record, e.g.: with or without an index.

Originally based upon relational algebra and tuple relational calculus, SQL consists of a data definition language, data manipulation language, and data control language. The scope of SQL includes data insert, query, update and delete, schema creation and modification, and data access control. Although SQL is often described as, and to a great extent is, a declarative language (4GL), it also includes procedural elements.

SQL was one of the first commercial languages for Edgar F. Codd's relational model, as described in his influential 1970 paper, "A Relational Model of Data for Large Shared Data Banks."[10] Despite not entirely adhering to the relational model as described by Codd, it became the most widely used database language.[11][12]

SQL became a standard of the American National Standards Institute (ANSI) in 1986, and of the International Organization for Standardization (ISO) in 1987.[13] Since then, the standard has been revised to include a larger set of features. Despite the existence of such standards, most SQL code is not completely portable among different database systems without adjustments.

History

SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce in the early 1970s.[14] This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasi-relational database management system, System R, which a group at IBM San Jose Research Laboratory had developed during the 1970s.[14] The acronym SEQUEL was later changed to SQL because "SEQUEL" was a trademark of the UK-based Hawker Siddeley aircraft company.[15]

In the late 1970s, Relational Software, Inc. (now Oracle Corporation) saw the potential of the concepts described by Codd, Chamberlin, and Boyce, and developed their own SQL-based RDBMS with aspirations of selling it to the U.S. Navy, Central Intelligence Agency, and other U.S. government agencies. In June 1979, Relational Software, Inc. introduced the first commercially available implementation of SQL, Oracle V2 (Version2) for VAX computers.

After testing SQL at customer test sites to determine the usefulness and practicality of the system, IBM began developing commercial products based on their System R prototype including System/38, SQL/DS, and DB2, which were commercially available in 1979, 1981, and 1983, respectively.[16]

Design

SQL deviates in several ways from its theoretical foundation, the relational model and its tuple calculus. In that model, a table is a set of tuples, while in SQL, tables and query results are lists of rows: the same row may occur multiple times, and the order of rows can be employed in queries (e.g. in the LIMIT clause).

Critics argue that SQL should be replaced with a language that strictly returns to the original foundation: for example, see The Third Manifesto.

Syntax

A chart showing several of the SQL language elements that compose a single statement

The SQL language is subdivided into several language elements, including:

Procedural extensions

SQL is designed for a specific purpose: to query data contained in a relational database. SQL is a set-based, declarative programming language, not an imperative programming language like C or BASIC. However, extensions to Standard SQL add procedural programming language functionality, such as control-of-flow constructs. These include:

Source Common name Full name
ANSI/ISO Standard SQL/PSM SQL/Persistent Stored Modules
Interbase / Firebird PSQL Procedural SQL
IBM DB2 SQL PL SQL Procedural Language (implements SQL/PSM)
IBM Informix SPL Stored Procedural Language
IBM Netezza NZPLSQL (based on Postgres PL/pgSQL)
Microsoft / Sybase T-SQL Transact-SQL
Mimer SQL SQL/PSM SQL/Persistent Stored Module (implements SQL/PSM)
MySQL SQL/PSM SQL/Persistent Stored Module (implements SQL/PSM)
MonetDB SQL/PSM SQL/Persistent Stored Module (implements SQL/PSM)
NuoDB SSP Starkey Stored Procedures
Oracle PL/SQL Procedural Language/SQL (based on Ada)
PostgreSQL PL/pgSQL Procedural Language/PostgreSQL Structured Query Language (implements SQL/PSM)
Sybase Watcom-SQL SQL Anywhere Watcom-SQL Dialect
Teradata SPL Stored Procedural Language
SAP SAP HANA SQL Script

In addition to the standard SQL/PSM extensions and proprietary SQL extensions, procedural and object-oriented programmability is available on many SQL platforms via DBMS integration with other languages. The SQL standard defines SQL/JRT extensions (SQL Routines and Types for the Java Programming Language) to support Java code in SQL databases. SQL Server 2005 uses the SQLCLR (SQL Server Common Language Runtime) to host managed .NET assemblies in the database, while prior versions of SQL Server were restricted to unmanaged extended stored procedures primarily written in C. PostgreSQL lets users write functions in a wide variety of languages—including Perl, Python, Tcl, JavaScript (PL/V8) and C.[18]

Interoperability and standardization

SQL implementations are incompatible between vendors and do not necessarily completely follow standards. In particular date and time syntax, string concatenation, NULLs, and comparison case sensitivity vary from vendor to vendor. Particular exceptions are PostgreSQL[19] and Mimer SQL[20] who strive for standards compliance.

Popular implementations of SQL commonly omit support for basic features of Standard SQL, such as the DATE or TIME data types. The most obvious such examples, and incidentally the most popular commercial and proprietary SQL DBMSs, are Oracle (whose DATE behaves as DATETIME,[21][22] and lacks a TIME type)[23] and MS SQL Server (before the 2008 version). As a result, SQL code can rarely be ported between database systems without modifications.

There are several reasons for this lack of portability between database systems:

SQL was adopted as a standard by the American National Standards Institute (ANSI) in 1986 as SQL-86[24] and the International Organization for Standardization (ISO) in 1987. It is maintained by ISO/IEC JTC 1, Information technology, Subcommittee SC 32, Data management and interchange. The standard is commonly denoted by the pattern: ISO/IEC 9075-n:yyyy Part n: title, or, as a shortcut, ISO/IEC 9075.

ISO/IEC 9075 is complemented by ISO/IEC 13249: SQL Multimedia and Application Packages (SQL/MM), which defines SQL based interfaces and packages to widely spread applications like video, audio and spatial data.

Until 1996, the National Institute of Standards and Technology (NIST) data management standards program certified SQL DBMS compliance with the SQL standard. Vendors now self-certify the compliance of their products.[25]

The original standard declared that the official pronunciation for "SQL" was an initialism: /ˈɛs kjuː ˈɛl/ ("es queue el").[11] Regardless, many English-speaking database professionals (including Donald Chamberlin himself[5]) use the acronym-like pronunciation of /ˈsiːkwəl/ ("sequel"),[26] mirroring the language's pre-release development name of "SEQUEL".[14][15] [5][14] The SQL standard has gone through a number of revisions:

Year Name Alias Comments
1986 SQL-86 SQL-87 First formalized by ANSI.
1989 SQL-89 FIPS 127-1 Minor revision that added integrity constraints, adopted as FIPS 127-1.
1992 SQL-92 SQL2, FIPS 127-2 Major revision (ISO 9075), Entry Level SQL-92 adopted as FIPS 127-2.
1999 SQL:1999 SQL3 Added regular expression matching, recursive queries (e.g. transitive closure), triggers, support for procedural and control-of-flow statements, non-scalar types (arrays), and some object-oriented features (e.g. structured types). Support for embedding SQL in Java (SQL/OLB) and vice versa (SQL/JRT).
2003 SQL:2003 Introduced XML-related features (SQL/XML), window functions, standardized sequences, and columns with auto-generated values (including identity-columns).
2006 SQL:2006 ISO/IEC 9075-14:2006 defines ways that SQL can be used with XML. It defines ways of importing and storing XML data in an SQL database, manipulating it within the database, and publishing both XML and conventional SQL-data in XML form. In addition, it lets applications integrate queries into their SQL code with XQuery, the XML Query Language published by the World Wide Web Consortium (W3C), to concurrently access ordinary SQL-data and XML documents.[27]
2008 SQL:2008 Legalizes ORDER BY outside cursor definitions. Adds INSTEAD OF triggers, TRUNCATE statement,[28] FETCH clause.
2011 SQL:2011 Adds temporal data (PERIOD FOR)[29] (more information at: Temporal database#History). Enhancements for window functions and FETCH clause.[30]
2016 SQL:2016 Adds row pattern matching, polymorphic table functions, JSON.

Interested parties may purchase SQL standards documents from ISO,[31] IEC or ANSI. A draft of SQL:2008 is freely available as a zip archive.[32]

The SQL standard is divided into nine parts.

ISO/IEC 9075 is complemented by ISO/IEC 13249 SQL Multimedia and Application Packages. This closely related but separate standard is developed by the same committee. It defines interfaces and packages based on SQL. The aim is a unified access to typical database applications like text, pictures, data mining or spatial data.

Alternatives

A distinction should be made between alternatives to SQL as a language, and alternatives to the relational model itself. Below are proposed relational alternatives to the SQL language. See navigational database and NoSQL for alternatives to the relational model.

Distributed SQL processing

Distributed Relational Database Architecture (DRDA) was designed by a work group within IBM in the period 1988 to 1994. DRDA enables network connected relational databases to cooperate to fulfill SQL requests.[35][36]

An interactive user or program can issue SQL statements to a local RDB and receive tables of data and status indicators in reply from remote RDBs. SQL statements can also be compiled and stored in remote RDBs as packages and then invoked by package name. This is important for the efficient operation of application programs that issue complex, high-frequency queries. It is especially important when the tables to be accessed are located in remote systems.

The messages, protocols, and structural components of DRDA are defined by the Distributed Data Management Architecture.

See also

Notes

  1. ↑ "Media Type registration for application/sql". Internet Assigned Numbers Authority. 10 April 2013. Retrieved 10 April 2013.
  2. ↑ "The application/sql Media Type, RFC 6922". Internet Engineering Task Force. April 2013. p. 3. Retrieved 10 April 2013.
  3. ↑ Paul, Ryan. "A guided tour of the Microsoft Command Shell". Ars Technica. Retrieved 10 April 2011.
  4. ↑ Beaulieu, Alan (April 2009). Mary E Treseler, ed. Learning SQL (2nd ed.). Sebastapol, CA, USA: O'Reilly. ISBN 978-0-596-52083-0.
  5. 1 2 3 Gillespie, Patrick. "Pronouncing SQL: S-Q-L or Sequel?". Pronouncing SQL: S-Q-L or Sequel?. Retrieved 12 February 2012.
  6. ↑ "SQL". Britannica.com. Retrieved 2013-04-02.
  7. ↑ "SQL". Oxforddictionaries.com. Retrieved 2017-01-16.
  8. ↑ "SQL Guide". Publib.boulder.ibm.com. Retrieved 2017-01-16.
  9. ↑ "Structured Query Language (SQL)". Msdn.microsoft.com. Retrieved 2017-01-16.
  10. ↑ Codd, Edgar F (June 1970). "A Relational Model of Data for Large Shared Data Banks". Communications of the ACM. Association for Computing Machinery. 13 (6): 377–87. doi:10.1145/362384.362685. Retrieved 2007-06-09.
  11. 1 2 Chapple, Mike. "SQL Fundamentals". Databases. About.com. Retrieved 2009-01-28.
  12. ↑ "Structured Query Language (SQL)". International Business Machines. October 27, 2006. Retrieved 2007-06-10.
  13. ↑ "ISO/IEC 9075-1:2016: Information technology – Database languages – SQL – Part 1: Framework (SQL/Framework)".
  14. 1 2 3 4 Chamberlin, Donald D; Boyce, Raymond F (1974). "SEQUEL: A Structured English Query Language" (PDF). Proceedings of the 1974 ACM SIGFIDET Workshop on Data Description, Access and Control. Association for Computing Machinery: 249–64. Retrieved 2007-06-09.
  15. 1 2 Oppel, Andy (February 27, 2004). Databases Demystified. San Francisco, CA: McGraw-Hill Osborne Media. pp. 90–1. ISBN 0-07-146960-5.
  16. ↑ "History of IBM, 1978". IBM Archives. IBM. Retrieved 2007-06-09.
  17. ↑ ANSI/ISO/IEC International Standard (IS). Database Language SQL—Part 2: Foundation (SQL/Foundation). 1999.
  18. ↑ PostgreSQL contributors (2011). "PostgreSQL server programming". PostgreSQL 9.1 official documentation. postgresql.org. Retrieved 2012-03-09.
  19. ↑ PostgreSQL contributors (2012). "About PostgreSQL". PostgreSQL 9.1 official website. PostgreSQL Global Development Group. Retrieved March 9, 2012. PostgreSQL prides itself in standards compliance. Its SQL implementation strongly conforms to the ANSI-SQL:2008 standard
  20. ↑ "Mimer SQL, Built on Standards". Mimer SQL official website. Mimer Information Technology. 2009.
  21. ↑ Lorentz, Diana; Roeser, Mary Beth; Abraham, Sundeep; Amor, Angela; Arora, Geeta; Arora, Vikas; Ashdown, Lance; Baer, Hermann; Bellamkonda, Shrikanth (October 2010) [1996]. "Basic Elements of Oracle SQL: Data Types". Oracle Database SQL Language Reference 11g Release 2 (11.2). Oracle Database Documentation Library. Redwood City, CA: Oracle USA, Inc. Retrieved December 29, 2010. For each DATE value, Oracle stores the following information: century, year, month, date, hour, minute, and second
  22. ↑ Lorentz, Diana; Roeser, Mary Beth; Abraham, Sundeep; Amor, Angela; Arora, Geeta; Arora, Vikas; Ashdown, Lance; Baer, Hermann; Bellamkonda, Shrikanth (October 2010) [1996]. "Basic Elements of Oracle SQL: Data Types". Oracle Database SQL Language Reference 11g Release 2 (11.2). Oracle Database Documentation Library. Redwood City, CA: Oracle USA, Inc. Retrieved December 29, 2010. The datetime data types are DATE...
  23. ↑ Lorentz, Diana; Roeser, Mary Beth; Abraham, Sundeep; Amor, Angela; Arora, Geeta; Arora, Vikas; Ashdown, Lance; Baer, Hermann; Bellamkonda, Shrikanth (October 2010) [1996]. "Basic Elements of Oracle SQL: Data Types". Oracle Database SQL Language Reference 11g Release 2 (11.2). Oracle Database Documentation Library. Redwood City, CA: Oracle USA, Inc. Retrieved December 29, 2010. Do not define columns with the following SQL/DS and DB2 data types, because they have no corresponding Oracle data type:... TIME
  24. ↑ "Finding Aid". X3H2 Records, 1978–95. American National Standards Institute.
  25. ↑ Doll, Shelley (June 19, 2002). "Is SQL a Standard Anymore?". TechRepublic's Builder.com. TechRepublic. Archived from the original on 2012-07-05. Retrieved 2016-04-12.
  26. ↑ Melton, Jim; Alan R Simon (1993). "1.2. What is SQL?". Understanding the New SQL: A Complete Guide. Morgan Kaufmann. p. 536. ISBN 1-55860-245-3. SQL (correctly pronounced "ess cue ell," instead of the somewhat common "sequel")...
  27. 1 2 Wagner, Michael (2010). SQL/XML:2006 - Evaluierung der Standardkonformität ausgewählter Datenbanksysteme. Diplomica Verlag. p. 100. ISBN 3-8366-9609-6.
  28. ↑ "SQL:2008 now an approved ISO international standard". Sybase. July 2008. Archived from the original on 2011-06-28.
  29. ↑ Krishna Kulkarni, Jan-Eike Michels (2012). "Temporal features in SQL:2011" (PDF).
  30. ↑ Fred Zemke (2012). "What's new in SQL:2011" (PDF).
  31. ↑ "ISO/IEC 9075-2:2016: Information technology -- Database languages -- SQL -- Part 2: Foundation (SQL/Foundation)". December 2016.
  32. ↑ "SQL:2008 draft" (Zip). Whitemarsh Information Systems Corporation.
  33. ↑ "ISO/IEC 9075-11:2008: Information and Definition Schemas (SQL/Schemata)". 2008: 1.
  34. ↑ Fernando Saenz-Perez. "Outer Joins in a Deductive Database System" (PDF). Lbd.udc.es. Retrieved 2017-01-16.
  35. ↑ Reinsch, R. (1988). "Distributed database for SAA". IBM Systems Journal. 27 (3): 362–389. doi:10.1147/sj.273.0362.
  36. ↑ Distributed Relational Database Architecture Reference. IBM Corp. SC26-4651-0. 1990.

References

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