SQL


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SQL

structured query language: a computer programming language used for database management

SQL

(computer science)

SQL

(language, database, standard)
/S Q L/ An industry-standard language for creating, updating and, querying relational database management systems.

SQL was developed by IBM in the 1970s for use in System R. It is the de facto standard as well as being an ISO and ANSI standard. It is often embedded in general purpose programming languages.

The first SQL standard, in 1986, provided basic language constructs for defining and manipulating tables of data; a revision in 1989 added language extensions for referential integrity and generalised integrity constraints. Another revision in 1992 provided facilities for schema manipulation and data administration, 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 persistent, complex objects. This includes: generalisation and specialisation hierarchies, multiple inheritance, user defined data types, triggers and assertions, support for knowledge based systems, recursive query expressions, and additional data administration tools. It also includes the specification of abstract data types (ADTs), object identifiers, methods, inheritance, polymorphism, encapsulation, and all of the other facilities normally associated with object data management.

The emerging 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".

SQL Standards.

An SQL parser is described in "Lex & Yacc", by Levine, Mason & Brown published by O'Reilly.

The 1995 SQL Reunion: People, Projects, and Politics.

["A Guide to the SQL Standard", C.J. Date, A-W 1987].

["SQL for Dummies", Allen G. Taylor, IDG Books Worldwide].

SQL

(Structured Query Language) Pronounced "S-Q-L" or "see-quill," a language used to interrogate and process data in a relational database. Originally developed by IBM for its mainframes, SQL commands can be used to interactively work with a database or can be embedded within a script or programming language to interface to a database. Programming extensions to SQL have turned it into a full-blown database programming language, and all major database management systems (DBMSs) support it.

ANSI standardized SQL, but most DBMSs have some proprietary enhancement, which if used, makes SQL non-standard. Moving an application from one SQL database to another sometimes requires tweaking, the age old problem in this business! See MySQL, MDX, CLI, ODBC, IDAPI and SQL injection.

The following SQL query selects customers with credit limits of at least $5,000 and puts them into sequence from highest credit limit to lowest. The blue words are SQL verbs. See SPUFI.

select name, city, state, zipcode
     from customer
     where creditlimit > 4999
     order by creditlimit desc



From Natural Language to SQL
English Wizard generated the SQL code at the bottom from the English sentence at the top. A lot of SQL code is required to ask a simple question. (Screen shot courtesy of EasyAsk Inc.)
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