SQL

SQL

Structured Query Language used to communicate with Oracle server, user communicates with Oracle server by sending commands/ instructions called queries.

A query is command or instruction submitted to Oracle server by the user to perform some operation over database.

This SQL language is introduced by IBM and initial name of this language was “SEQUEL” and later it is renamed to SQL. It is now under control of ANSI.

SQL is common to all Databases.

Based on operations over database SQL is categorized into following sub languages:

DDL: - Data Definition Language

DML: - Data Manipulation Language

DQL: - Data Query Language

TCL: - Transaction Control Language

DCL: - Data Control Language

Data & Definition: - Facts about person’s, places, events are called as data.

Ex: - 1, Shri, 5000

○ Facts are described by definition that is known as data definition or Meta data.

Meta data: - Data  about Data

DDL: - Set of commands to perform operations over data definition.

DDL COMMANDS

  DML: - Set of commands to perform operations over data.

DML COMMANDS

DQL: - Command used to get data from database.

            SELECT

TCL: - Set of commands to control transactions (dual operations).

TCL COMMANDS

DCL: - Set of commands to control data.

DCL COMMANDS

Tools

Used to execute SQL commands are:

SQL PLUS / TOAD / SQL DEVELOPER

○ SQL commands are not case sensitive.

○ SQL commands must be terminated with ' ; '