Learn Oracle/SQL

Oracle Overview

What is oracle?

Oracle corporation is a company that produces the database product which is widely used, server based and multi user known as ORACLE.

Some more points to make you more clear about ORACLE are:

• Oracle is a product by Oracle Corporation.
• Oracle is an Object Relational Database Management System(RDBMS).
• The first version was introduced in the year 1982, was called Oracle 2.

Next topic will teach you how oracle communicate with server.

What is SQL?

SQL - SQL stands for Structured Query Language, is a fourth generation non procedural language introduced by IBM and was standardized by ANSI(American Nationl Standards Institute) and ISO in 1986.

Below are the points to make you more clear about SQL are:

• SQL is a language for communicating with the Oracle Server to access data.
• When an SQL statement is entered, it is stored in a part of memory called the SQL buffer and remains there until a new SQL statement is entered.
• SQL manipulates data and table defination in the database.
• It has nine commands which are common to all RDBMS.

There are some COMPONENTS OF SQL as follows:

• DDL (Data Defination Language)
• DML (Data Manipulation Language)
• DCL (Data Control Language)

What is SQL *Plus?

SQL *Plus is an extension to SQL. It has been introduced to eliminate SQL limitations. It has many commands, you can say hundreds of SQL commands.

Some usefull points are as mentioned below for SQL *Plus:

• SQL *Plus can be used to setting up the environment.
• SQL *Plus can accepts ad hoc entry of statements.
• SQL *Plus is the Oracle built in interface for executing SQL statements.
• SQL *Plus provide a line editor for modifying SQL statements.

Start by Select Statement

The above tools are used to access oracle database which resides on oracle server. Now we should have little information about Oracle database from where we are going to fetch data.

What is Database?

A Database is a collection of related and meaningful data. Take an example of company and a employee.

An employee contains:

• Employee Id
• Department
• Salary
• Age
• Designation

Suppose above information is collected for multiple employees. And all the employee information is available at one place known as company.
Now as we all know, company contains employee information which is related to it.
Hence we can say that company is a database and employee detail is a data which fills database.