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Lexikon

SQL

/S Q L/ An industry-standard language for creating, updating and, querying {relational database management systems}. SQL was developed by href="module.php?name=Lexikon&file=search&eid=1&query=IBM">IBM in the 1970s for use in href="module.php?name=Lexikon&file=search&eid=1&query=System R">System R. It is the href="module.php?name=Lexikon&file=search&eid=1&query=de facto standard">de facto standard as well as being an href="module.php?name=Lexikon&file=search&eid=1&query=ISO">ISO and href="module.php?name=Lexikon&file=search&eid=1&query=ANSI">ANSI href="module.php?name=Lexikon&file=search&eid=1&query=standard">standard. It is often embedded in general purpose programming languages. The first SQL standard, in 1986, provided basic language constructs for defining and manipulating href="module.php?name=Lexikon&file=search&eid=1&query=tables">tables of data a revision in 1989 added language extensions for {referential integrity} and generalised {integrity} {constraints}. Another revision in 1992 provided facilities for href="module.php?name=Lexikon&file=search&eid=1&query=schema">schema manipulation and href="module.php?name=Lexikon&file=search&eid=1&query=data chefistration">data chefistration, as well as substantial enhancements for data definition and data manipulation. Development is currently underway to enhance SQL into a computationally complete language for the definition and management of href="module.php?name=Lexikon&file=search&eid=1&query=persistent">persistent, complex objects. This includes: generalisation and specialisation hierarchies, {multiple inheritance}, user defined {data types}, {triggers} and href="module.php?name=Lexikon&file=search&eid=1&query=assertions">assertions, support for href="module.php?name=Lexikon&file=search&eid=1&query=knowledge based systems">knowledge based systems, href="module.php?name=Lexikon&file=search&eid=1&query=recursive query expressions">recursive query expressions, and additional data chefistration tools. It also includes the specification of href="module.php?name=Lexikon&file=search&eid=1&query=abstract data types">abstract data types (ADTs), object identifiers, href="module.php?name=Lexikon&file=search&eid=1&query=methods">methods, href="module.php?name=Lexikon&file=search&eid=1&query=inheritance">inheritance, href="module.php?name=Lexikon&file=search&eid=1&query=polymorphism">polymorphism, href="module.php?name=Lexikon&file=search&eid=1&query=encapsulation">encapsulation, and all of the other facilities normally associated with object data management. The emerging href="module.php?name=Lexikon&file=search&eid=1&query=SQL3">SQL3 standard is expected to be complete in 1998. According to Allen G. Taylor, SQL does _not_ stand for "Structured Query Language". That, like "SEQUEL" (and its pronunciation /see' kw*l/), was just another unofficial name for a precursor of SQL. However, the IBM SQL Reference manual for DB2 and Craig Mullins' s "DB2 Developer' s Guide" say SQL _does_ stand for "Structured Query Language". href="http://www.jcc.com/sql_stnd.html">SQL Standards . {An SQL parser (ftp://ftp.ora.com/published/oreilly/nutshell/lexyacc/)} is described in "Lex & Yacc", by Levine, Mason & Brown published by O' Reilly. {The 1995 SQL Reunion: People, Projects, and Politics (http://www.mcjones.org/System_R/SQL_Reunion_95/)}. ["A Guide to the SQL Standard", C.J. Date, A-W 1987]. ["SQL for Dummies", Allen G. Taylor, IDG Books Worldwide]. (2005-11-17)

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