DBMS Handwritten Notes - Basics Made Easy

INTRODUCTION

• A DBMS is software that helps store, manage, and retrieve data efficiently.

• It acts as a bridge between users/applications and the data.

• Common examples include MySQL, Oracle, MongoDB, PostgreSQL, and SQLite.

DBMS Key Features

• Data Abstraction: Hides complex details, shows only necessary views.

• Data Integrity: Ensures accuracy and consistency of data.

• Data Security: Controls access using authentication and permissions.

• Concurrency Control: Supports multiple users accessing data simultaneously.

• Backup & Recovery: Automatically manages data protection and restoration.

TYPES OF DBMS

• Hierarchical DBMS: Data stored in tree-like structures (e.g., IBM IMS).

• Network DBMS: More flexible; supports complex relationships using graphs.

• Relational DBMS (RDBMS): Data stored in tables (rows & columns). Most popular (e.g., MySQL, PostgreSQL).

• Object-oriented DBMS: Stores objects, supports classes and inheritance.

• NoSQL DBMS: For unstructured/large-scale data (e.g., MongoDB, Cassandra).

DBMS VS. FILE SYSTEM

• DBMS handles relationships, security, and reduces redundancy.

• File systems are simple but lack constraints and are harder to scale/manage.

COMPONENTS OF A DBMS

• DB Engine: Core software handling storage, processing, and queries.

• Query Processor: Interprets SQL commands.

• Database Schema: Defines structure—tables, keys, and relationships.

• Transaction Manager: Ensures ACID properties.

• Data Dictionary: Metadata about data — types, sizes, constraints.

ACID PROPERTIES

• Atomicity: All or none.

• Consistency: Always leaves DB in a valid state.

• Isolation: Transactions don’t interfere.

• Durability: Once committed, changes persist.

COMMON USES

• Web applications (e.g., storing user data)

• E-commerce (managing inventory, orders)

• Banking systems (transactions, balances)

• Hospitals (patient records)

• Education (student management systems)

What You Should Remember

• A DBMS makes it easier and safer to manage large volumes of data.

• Choosing the right DBMS depends on your use case—structured data, speed, scalability, etc.

• Understanding DBMS is critical for developers, data analysts, and system architects.