 The
paper, "A
Relational Model of Data for Large Shared Data Banks," by Dr. E. F. Codd,
was published in June 1970 in the Association of Computer Machinery (ACM)
journal, Communications of the ACM. Codd’s model is now accepted as the
definitive model for relational database management systems (RDBMS). The
language, Structured English Query Language ("SEQUEL") was developed
by IBM Corporation, Inc., to use Codd’s model. SEQUEL later became SQL (still
pronounced "sequel"). In 1979, Relational Software, Inc. (now Oracle
Corporation) introduced the first commercially available implementation of SQL.
Today, SQL is accepted as the standard RDBMS language.The strengths of SQL
benefit all types of users, including application programmers,database
administrators, management, and end users. Technically speaking, SQL is a data
sublanguage: the purpose of SQL is to provide an interface to a relational
database such as Oracle, and all SQL statements are instructions to the database.
In this it differs from general-purpose programming languages like C and BASIC.
Among the features of SQL are the following: It processes sets of data as
groups rather than as individual units. It provides automatic navigation to the
data. It uses statements that are complex and powerful individually, and that
therefore stand alone. Flow-control statements were not part of SQL originally,
but they are found in the recently accepted optional part of SQL,
ISO/IEC 9075-5: 1996. Flow-control statements are commonly known as "persistent
stored modules" (PSM), and Oracle’s PL/SQL extension to SQL is close to
PSM. Essentially, SQL lets you work with data at the logical level. You need to
be concerned with the implementation details only when you want to manipulate
the data. For example, to retrieve a set of rows from a table, you define a
condition used to filter the rows. All rows satisfying the condition are
retrieved in a single step and can be passed as a unit to the user, to another
SQL statement, or to an application. You need not deal with the rows one by
one,
nor do you have to worry about how they are physically stored or retrieved. All
SQL statements use the optimizer, a part of Oracle that determines a fast means
of accessing the specified data. Oracle also provides techniques you can use to
make the optimizer perform its job better. SQL provides commands for a variety
of tasks, including: querying data, inserting, updating, and
deleting rows in a table, creating, replacing, altering, and dropping
objects, controlling access to the database and its objects,, guaranteeing
database consistency and integrity SQL unifies all of the above tasks in one
consistent lanG. |
Oracle
Corporation was founded in 1977 in Redwood, California. They introduced
the first Relational Database Management System based on the IBM System/R
model and the first database management system utilizing IBM's Structured
Query Language (SQL) technology.
Today, the Oracle DBMS is supported on over 80 different operating environments, ranging from IBM mainframes, DEC VAX minicomputers, UNIX-based minicomputers, Windows NT and several proprietary hardware-operating system platforms, and is clearly the world's largest RDBMS vendor. Oracle employs more than 42,000 professionals in 93 countries around the world. Their expenditure for research and development is approximately 13% of their revenues
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