Database Management System

A Database Management System (DBMS) is software that allows users to store, manage, and retrieve data efficiently while ensuring security and consistency.

🧠 Core Idea of Database

• What data is stored?
• How is data accessed?
• How is data maintained?

🏗️ Structure of Database

Tables (Relations), Rows (Tuples), Columns (Attributes)

Roll No	Name	Dept	GPA
101	Ali	CS	3.5
102	Sara	SE	3.8

⚙️ Characteristics

• Data Persistence
• Data Independence
• Reduced Redundancy
• Data Integrity
• Concurrency Control
• Security Control

🧩 Types of Databases

• Relational Database (MySQL, Oracle)
• NoSQL (MongoDB, Redis, Cassandra)
• Distributed Database
• Cloud Database ☁️
• Centralized Database

🔗 ER Diagram

Entities = objects, Attributes = properties, Relationships = connections

Example: Student → Enrolls → Course

🔑 Keys

• Primary Key: Unique identifier
• Candidate Key: Possible unique keys
• Foreign Key: Links tables

⚙️ Normalization

• 1NF → Atomic values
• 2NF → Remove partial dependency
• 3NF → Remove transitive dependency

💻 SQL Queries

SELECT * FROM Student;

INSERT INTO Student (RollNo, Name)
VALUES (101, 'Ali');

UPDATE Student
SET Name = 'Ahmed'
WHERE RollNo = 101;

DELETE FROM Student
WHERE RollNo = 101;
    

🔗 JOIN Example

SELECT Student.Name, Marks.Score
FROM Student
INNER JOIN Marks
ON Student.RollNo = Marks.RollNo;
    

DBMS is used in banking systems, social media apps, e-commerce platforms, and university management systems.