Oracle SQL Overview
This overview aims to answer the questions what is Oracle SQL, what is
it used for and how do I use it.
What is Oracle SQL?SQL
is the language used with Oracle and other databases to extract
information from the database and to modify the information in the
database. It is used by application programs, developers and dbas and
is used by all the Oracle tools.
SQL
was invented by Dr. E.F.
Codd at IBM in the 1970s to go with the then new concept of relational
databases. The language was designed to be an end-user query tool and
is based on set theory making it easy to
understand and use but very different from programming languages such
as Java or C++.
SQL has been used with Oracle
databases since the first release of Oracle and in Oracle 10g and
Oracle 11g is based on the most recent ANSI/ISO standard ANSI/ISO/IEC
9075:2003, "Database Language SQL" (refer to Ax. B. of
Oracle SQL Reference for the details of Oracle's conformance with the
standard).
What Features Does The Language Provide?SQL is actually comprised of 3 sub-languages
each designed for a different purpose:
- Data Manipulation Language (DML) - this is the
most commonly used sub language and is designed to enable users of the
database (including applications) to retrieve information stored in the
database, to modify and remove existing data and to create new
data.
- Data
Definition Language (DDL) - this is designed to enable users to create,
modify and remove the meta-data of the database that is the individual
physical and logical data structures such as tables, views, procedures,
functions, indexes, tablespaces, datafiles etc
- Data Control
Language (DCL) - this is designed to enable privileges and roles to be
granted to users. Privileges include system privileges which enable the
user to perform specific actions (such as shut down the database or
create new data structures) and data privileges which enables
the
user to read, modify or create data in the database.
Oracle SQL also enables non-relational data
including object types, XML, collections (such as nested
tables) and LOBs (large objects) such as video files to be stored,
queried and modified.
How To Use Oracle SQL
Oracle provides a number of tools that process SQL commands to enable
interaction with the database:
- Oracle
SQL Developer - this is a tool that provides a graphical interface to
the specified database (Oracle, MySQL, Access or SQLServer) and enables
you to view and modify data, create new database objects, run SQL and
PL/SQL scripts as well as export data and generate reports.
- SQL*Plus - this tool has been around for many
years and the interface hasn't changed much in that time. SQL*Plus is
simple to use if you already know SQL, but it doesn't offer much
help if you make a mistake. It offers a command line for entering SQL
and PL/SQL statements or running SQL or PL/SQL scripts.
- Oracle JDeveloper - this provides a Java
development environment but also provides a graphical interface to the
database for running SQL and PL/SQL statements as well as a
visual database modeler.
- Oracle Application Express (previously called
HTMLDB) - this provides a development environment for web applications
and includes the ability to process SQL commands.
This was just a brief overview of SQL. For a more detailed
introduction
to the language see our Oracle SQL
tutorial.
Full details of syntax and usage
are provided by the OracleŽ SQL Language
Reference available from the Oracle Technology
Network.
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