(pronounced "ess-que-el") stands for Structured Query Language. SQL
is used to communicate with a database. According to ANSI (American National
Standards Institute), it is the standard language for relational database
management systems. SQL statements are used to perform tasks such as update
data on a database, or retrieve data from a database. Some common relational
database management systems that use SQL are: Oracle, Sybase, Microsoft SQL
Server, Access, Ingres, etc. Although most database systems use SQL, most of
them also have their own additional proprietary extensions that are usually
only used on their system. However, the standard SQL commands such as
"Select", "Insert", "Update", "Delete",
"Create", and "Drop" can be used to accomplish almost
everything that one needs to do with a database. This tutorial will provide you
with the instruction on the basics of each of these commands as well as allow
you to put them to practice using the SQL Interpreter.
SQL ( /ˈsiːkwəl/ "sequel"; Structured
Query Language) 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). It is particularly useful in
handling structured data where there are relations between
different entities/variables of the data. SQL offers two main advantages over
older read/write APIs like ISAM or VSAM.
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.
algebra and tuple
SQL consists of many types of statements, which
may be informally classed as sublanguages, commonly: a data query
language (DQL),[a] a data
definition language (DDL),[b] a data
control language (DCL),
and a data
manipulation language (DML).[c] The
scope of SQL includes data query, data manipulation (insert, update and
delete), data definition (schemacreation and modification), and data access control.
Although SQL is often described as, and to a great extent is, a declarative
it also includes procedural elements.
SQL was one of the
first commercial languages for 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". Despite not entirely adhering to the relational model as described by Codd, it became the most widely used database
SQL became a standard of the American National Standards Institute (ANSI) in 1986, and of the International Organization for Standardization (ISO) in 1987. 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
SQL was initially
developed at IBM by Donald D.
Chamberlin and Raymond F. Boyce after learning about the relational model
from Ted Codd in the early 1970s. 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.
Boyce's first attempt of a relational database language was Square, but it was
difficult to use due to subscript notation. After moving to the San Jose
Research Laboratory in 1973, they began work on SEQUEL. The acronym SEQUEL was later changed to SQL because
"SEQUEL" was a trademark of the UK-basedHawker Siddeley Dynamics Engineering Limited company.
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.
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.
By 1986, ANSI and ISO standard
groups officially adopted the standard "Database Language SQL"
language definition. New versions of the standard were published in 1989, 1992,
1996, 1999, 2003, 2006, 2008, 2011, and most recently, 2016.
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SQL (pronounced "ess-que-el") stands for
System/38 , SQL/DS , and DB2 , which were commercially available in 1979, 1981, and 1983, respectively