What is SQL?
SQL stands for Structured Query Language. It is used to:
SELECT data from tables
INSERT new data into tables
UPDATE existing records
DELETE unwanted data
Manage database objects like tables, users, and views
Control access rights and permissions
SQL – The Gateway to the Database
SQL is the primary way to interact with a relational database. Think of it as the window to the database — without it, you can’t retrieve, manipulate, or store data in Oracle or any RDBMS.
It’s a 4GL (Fourth Generation Language) — designed to be simple, efficient, and user-friendly, especially compared to older, more complex languages.
A Brief History of SQL
SQL was not created by Oracle.
It evolved from the work of Dr. E.F. Codd and IBM in the 1970s.
Today, it is standardized by ANSI (American National Standards Institute).
Oracle supports ANSI SQL but adds enhancements via its SQL*Plus tools.
SQL*Plus – Oracle's SQL Interface
Oracle provides SQL*Plus as a utility to run SQL and PL/SQL commands. It comes in multiple forms:
- Command Line – via DOS or Unix terminal
GUI Tools – like SQL Developer, SQL Worksheet, or Enterprise Manager
Web-Based – iSQL*Plus (available from Oracle 10g onward)
These tools allow you to connect and interact with both local and remote Oracle databases.
SQL Syntax Examples:
-- SELECT: Fetch records
SELECT first_name, salary FROM employees WHERE department_id = 10;
-- INSERT: Add a new row
INSERT INTO employees (employee_id, first_name, salary)
VALUES (101, 'Amit', 50000);
-- UPDATE: Change existing data
UPDATE employees SET salary = 60000 WHERE employee_id = 101;
-- DELETE: Remove a row
DELETE FROM employees WHERE employee_id = 101;
Types of SQL Statements
SQL commands can be grouped into five main categories:
Data Query Language (DQL)
Used to query the database.
Examples:
SELECT * FROM employees;
  2. Data Definition Language (DDL)
Used to define and modify database structure.
Commands:
CREATE,ALTER,DROP,TRUNCATE
Examples:
CREATE TABLE students (id NUMBER, name VARCHAR2(50));
  3. Data Manipulation Language (DML)
Used to manipulate data within tables.
Commands:
INSERT,UPDATE,DELETE
Examples:
UPDATE employees SET salary = 55000 WHERE id = 101;
  4. Transaction Control Language (TCL)
Manages transactions in the database.
Commands:
COMMIT,ROLLBACK,SAVEPOINT
Examples:
COMMIT;
  3. Data Control Language (DCL)
Controls access to data.
Commands:
GRANT,REVOKE
Examples:
GRANT SELECT ON employees TO hr_user;
Tools to Run SQL in Oracle
| Tool | Description |
|---|---|
| SQL*Plus CLI | Command-line interface for running SQL & PL/SQL commands |
| iSQL*Plus | Web-based version of SQL*Plus (Oracle 10g) |
| SQL Developer | GUI tool for running and debugging SQL/PLSQL |
| Enterprise Manager | Web GUI to monitor and manage the database |
Why Learn SQL?
SQL is universal across databases like MySQL, Oracle, PostgreSQL, SQL Server.
Knowing SQL is a core skill for developers, DBAs, analysts, and testers.
It forms the foundation of PL/SQL and many backend systems.
