SQL

1. SQL is generic to most true relational database management systems (RDBMS's) and is an ANSI standard.
2. SQL is the language used to access the data and structures within a relational database. PL/SQL (an Oracle specific SQL extension) allows basic program logic and
control flow to be implemented around SQL statements.
3. Most RDBMS vendors have a similar set of extensions or allow SQL statements to be embedded within a normal development package such as Visual Basic or C++.

SQL Features

It is meant to be an English like language using set English phrases to manipulate the database. How well it achieves this is questionable.

It is non procedural. You specify the information required not the navigation and operations required to access the data. Each RDBMS has an inbuilt query optimizer which parses your SQL statements and works out the optimum path to the required data.

When you query data, all the rows affected by your statement are dealt with in one go as a set, they are not dealt with separately. The work area that holds the set is known as a CURSOR.

SQL encompasses a range of uses and users. DBA's, application programmers, management and end users can use SQL.

It provides commands for the following tasks:-

• Quering Data.
• Inserting, Updating and Deleting Data.
• Creating. Modifying and Deleting Database Objects.
• Controlling Access to the Database and Database Objects.
• Guaranteeing Database Consistency.
• Monitoring Database Performance and Configurations.

Standard SQL statements can be subdivided into 4 distinct groups which are shown below,

DQL

Data Query Language - SELECT Statement

DML

Data Manipulation Language - Delete, Insert, Update

DDL

Data Definition Language - Create, Alter, Truncate, Drop

RIGHTS

For giving and taking back the access rights to database objects.

Grant and Revoke.

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-Murali..