Database Management Systems

Introduction

Database Management Systems (DBMS) are software systems designed to store, retrieve, and manage data in databases. They provide an interface between the database and its end users or application programs.

Key Concepts:

  • Data independence
  • Concurrent access
  • Data integrity
  • Data security
  • Backup and recovery
  • Query optimization

Types of Databases

Relational Databases

Structured data organized in tables with rows and columns:

Popular RDBMS:

  • MySQL - Open-source, widely used
  • PostgreSQL - Advanced features, extensible
  • SQL Server - Microsoft's enterprise solution
  • Oracle - Enterprise-grade, high performance

NoSQL Databases

Non-relational databases for flexible data structures:

Types of NoSQL:

  • Document stores (MongoDB)
  • Key-value stores (Redis)
  • Wide-column stores (Cassandra)
  • Graph databases (Neo4j)

Database Design

Normalization

The process of organizing data to minimize redundancy:

-- Example of a normalized schema
CREATE TABLE Customers (
    customer_id INT PRIMARY KEY,
    name VARCHAR(100),
    email VARCHAR(100)
);

CREATE TABLE Orders (
    order_id INT PRIMARY KEY,
    customer_id INT,
    order_date DATE,
    FOREIGN KEY (customer_id) REFERENCES Customers(customer_id)
);

Relationships

Types of Relationships:

  • One-to-One (1:1)
  • One-to-Many (1:N)
  • Many-to-Many (M:N)

Data Modeling

Conceptual Model

High-level view of data relationships using Entity-Relationship (ER) diagrams.

Logical Model

Detailed representation of entities, attributes, and relationships.

Physical Model

Example of physical implementation:

-- Physical implementation example
CREATE TABLE Products (
    product_id INT PRIMARY KEY,
    name VARCHAR(100),
    price DECIMAL(10,2),
    category_id INT,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    INDEX idx_category (category_id),
    FOREIGN KEY (category_id) REFERENCES Categories(id)
);

Implementation

Query Optimization

Example of optimizing queries:

-- Optimized query with proper indexing
EXPLAIN SELECT p.name, c.category_name
FROM Products p
INNER JOIN Categories c ON p.category_id = c.id
WHERE p.price > 100.00
    AND c.category_name LIKE 'Electronics%';

Transaction Management

ACID Properties:

  • Atomicity
  • Consistency
  • Isolation
  • Durability

Best Practices

Design Guidelines

Key Principles:

  • Proper indexing strategy
  • Normalization when appropriate
  • Consistent naming conventions
  • Regular backups
  • Performance monitoring
  • Security best practices

Performance Optimization

Optimization Tips:

  • Use appropriate data types
  • Implement proper indexes
  • Optimize queries
  • Regular maintenance
  • Caching strategies