Introduction to Databases and SQL

What is a Database?

A database is an organized collection of data that can be easily accessed, managed, and updated. Databases store information in a structured format, allowing users to retrieve and manipulate data efficiently. They are widely used in various applications, including websites, mobile apps, financial systems, and enterprise software.

Types of Databases

1. Relational Databases (RDBMS) – Store data in tables with relationships. Examples: MySQL, PostgreSQL, SQL Server.
2. NoSQL Databases – Handle unstructured or semi-structured data. Examples: MongoDB, Cassandra.
3. In-Memory Databases – Store data in RAM for fast access. Examples: Redis, Memcached.

What is SQL?

SQL (Structured Query Language) is a standard language used to interact with relational databases. It allows users to create, read, update, and delete (CRUD) data using structured queries.

Common SQL Commands

• DDL (Data Definition Language) – Defines and modifies database structures.
  • CREATE TABLE, ALTER TABLE, DROP TABLE
• DML (Data Manipulation Language) – Handles data within tables.
  • SELECT, INSERT, UPDATE, DELETE
  • DCL (Data Control Language) – Manages access permissions.
• GRANT, REVOKE
• TCL (Transaction Control Language) – Manages transactions.
  • COMMIT, ROLLBACK, SAVEPOINT

Why Use SQL?

1. Data Integrity – Ensures data accuracy and consistency.
2. Efficiency – Optimized for handling large datasets.
3. Scalability – Used in small applications and enterprise-level systems.
4. Flexibility – Works with different database systems.

Basic SQL Example

CREATE TABLE Students (
    id INT PRIMARY KEY,
    name VARCHAR(100),
    age INT,
    course VARCHAR(50)
);

INSERT INTO Students (id, name, age, course)
VALUES (1, 'Rahul Sharma', 21, 'Computer Science');

SELECT * FROM Students;

This example creates a Students table, inserts a record, and retrieves all data.

Conclusion

Databases and SQL are fundamental to modern applications. Understanding how to work with SQL enables efficient data management. In the next tutorial, we will cover Creating and Managing Tables in SQL.