Changes of Selected Statement

Structured Query Language is the standard language for database management systems as defined by the American National Standards Institute (ANSI).

SQL is a very simple, yet powerful, non procedural language for communicating with the Oracle server. All operations executed within the Oracle database are performed using SQL statements.

What is Structured Query Language?

SQL provides a comprehensive set of commands for a variety of tasks, including the following:

Querying data
Updating, Inserting and deleting data
Creating, modifying, and deleting database objects
Controlling access to the database
Providing for data integrity and consistency

Why use Structured Query Language?

SQL is a very powerful language that benefits all types of users of the Oracle database. The following groups of individuals benefit from SQL:

Database administrators
Application developers
Database security administrators
End users

SQL is a very flexible language that enables you to accomplish your development efforts. SQL enables you to work with large groups of data rather than restricting you to single rows of data.

Additionally, SQL allows for the results of one query to be the input to another query statement. SQL removes from you the burden of deciding on the correct access methods. Oracle uses its own internal optimizer to , determine the fastest and best means of accessing data. This simplifies your application and reduced development overhead.

By defining SQL as the main database access. language, Oracle eliminates the potential of security and data compromise.

How to use SQL?

SQL is the primary means of communicating with the Oracle database.

SQL*Plus does not care it your commands are typed in upper or lowercase. Both cases are treated equally except when performing a comparison.

SQL statements begin with the SQL command, followed by the remainder of the statement. For example, the following SQL statement uses the SQL command drop table to remove the table object from the database.

drop table emp;
When the Oracle server generates an error code, it is in the following structure: error : error code : error description

Naming Objects

Many of the Oracle objects are made up of parts that must be named by you when you create the object. The following rules apply to object names as well as to database usernames :

Names must be between I and 30 bytes. Database names are limited to eight bytes; database links can be up to 128 bytes.
Names cannot be in quotation marks.
Names are not case sensitive. This means that it doesn't make any difference if a name is in upperor lowercase letters.
The name must begin with an alphabetic character and can contain only alphanumeric characters.
A name cannot be an Oracle or SQL reserved word.

SQL and SQL*PLUS

SQL is the native language of the Oracle server. It is the language used to communicate with the database. ANSI has adopted SQL as the standard language for relational database management systems.

SQL*Plus is an Oracle server tool that recognizes and executes SQL statements. SQL*Plus is not an extension or superset of SQL.

SQL*Plus is one of the most common ways to communicate interactively with the Oracle database. One of the benefit of SQL*Plus is that you can edit or save the SQL commands that are in the buffer.

The SQL buffer is part of memory managed by SQL*Plus that stores one SQL command at a time. A single SQL command remains in the SQL buffer until a new command is issued.

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