Tra từ SQL - Từ điển Máy Tính

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].

Last updated: 2005-11-17