1.
Definition and Purpose of Databases
Definition:
A database is an organized collection of data that is stored electronically and managed using a
database management system (DBMS). It allows efficient retrieval, storage, and manipulation of
data to support various applications.
Purpose of Databases:
Data Organization: To store data in a structured and meaningful way.
Data Accessibility: To provide users and applications with quick and efficient access to
information.
Data Sharing: To enable multiple users to access and share data concurrently.
Data Security: To protect data against unauthorized access.
Data Consistency: To ensure that updates are properly reflected across all parts of the
database.
Example:
Online Banking: A database is used to store customer account details, transaction
histories, and loan information.
1. Definition and Purpose of Databases
A database is an organized collection of data stored and managed to allow easy access, retrieval,
and manipulation.
Purpose of Databases:
o Efficiently manage large volumes of data.
o Support multiple users simultaneously.
o Ensure data consistency and accuracy.
o Facilitate data security and integrity.
o Simplify data sharing across applications.
2. Characteristics of Database Systems
Database systems have several features that make them efficient and reliable:
1. Data Abstraction:
o Hides the complexity of data storage from users.
o Example: Users of an e-commerce platform only see product details, not how
they're stored.
2. Data Independence:
o Changes in storage mechanisms do not affect the application's ability to access the
data.
o Example: A database can shift from hard drives to cloud storage without affecting
user queries.
3. Data Integrity:
o Ensures accuracy and consistency of data through constraints.
o Example: Enforcing a rule that "employee ID" must be unique across all entries.
4. Concurrency Control:
o Allows multiple users to access the database simultaneously without conflicts.
o Example: Two customers placing orders on Amazon without interfering with each
other’s data.
5. Backup and Recovery:
o Protects data from loss due to hardware failures or human errors.
o Example: Automatic nightly backups of a company's sales database.
6. Data Security:
o Restricts unauthorized access to sensitive data.
o Example: Only HR personnel can view salary details in a company database.
3. File System vs. Database System
Aspect File System Database System
High; data is often duplicated in Low; redundant data is minimized
Data Redundancy
multiple files. through normalization.
Ensured using constraints and
Data Consistency Hard to enforce across files.
relationships.
Concurrency Limited; multiple accesses often
Built-in support for concurrent access.
Control cause data corruption.
Minimal or relies on operating
Security Advanced access control mechanisms.
system permissions.
Querying Requires custom scripts for retrieval. Standardized querying using SQL.
Example:
File System: Storing employee details in separate Excel files for each department.
Database System: Storing all employee details in a single relational database with proper
relationships.
4. Database Users
1. End Users:
o Use the database to perform tasks such as retrieving, updating, or inserting data.
o Example:
A student accessing their grades via a university portal.
A customer searching for products on an e-commerce site.
2. Database Administrators (DBAs):
o Responsible for managing the database, ensuring performance, security, and
availability.
o Example:
Configuring user access roles in a company database.
Performing backups and restoring data during system failures.
3. Developers:
o Design and create database structures and write applications that interact with the
database.
o Example:
A software developer creating an application for hospital patient
management that interacts with a database.
5. Database Applications and Examples
Databases are used in various fields for data management and operational efficiency:
1. Banking:
Used for account management, transactions, and customer services.
Example: Core banking systems like Oracle Financial Services.
2. Healthcare:
Stores patient records, prescriptions, and scheduling.
Example: Hospital databases like those used in Electronic Medical Records (EMRs).
3. Education:
Tracks student details, grades, and attendance.
Example: Student Information Systems (SIS) like Blackboard or Moodle.
4. E-commerce:
Manages product inventory, customer information, and sales data.
Example: Databases used by Amazon or Flipkart to manage millions of products.
5. Transportation:
Stores and tracks ticket bookings, schedules, and passenger data.
Example: Airline reservation systems like Sabre or Amadeus.
6. Social Media:
Manages user profiles, posts, and connections.
Example: Facebook uses graph databases to handle complex relationships between users.
2. Database Architecture
Database architecture refers to the structure or design of a database system. It defines how data is
organized, accessed, managed, and processed. . It is a conceptual blueprint for how the database
components interact with one another and external users. Efficient architecture is essential for
ensuring scalability, security, and performance.
1. Three-tier Architecture (External, Conceptual, Internal)
This architecture divides the database system into three levels to separate user interactions from
data storage and ensure flexibility and security.
The three-tier architecture separates the database system into three levels to achieve data abstraction
and independence:
External Level (User View):
This level provides a customized view of the database to individual users or applications.
Each user interacts with the database through a tailored interface, hiding irrelevant details.
Example:
A sales manager sees only customer names and sales data.
A warehouse manager sees inventory details but not customer information.
o
o (e.g., a sales team sees customer and order data but not employee salaries).
o
Conceptual Level (Logical View):
o Represents the entire database schema and logical structure.
o Defines entities, relationships, and constraints.
o Independent of how data is stored physically.
Internal Level (Physical View):
o Focuses on the physical storage of data.
o Deals with how data is organized on disks (e.g., indexing, file structures).
o Ensures data is stored efficiently and securely.
Advantages of Three-tier Architecture:
Provides data abstraction, hiding complexity from users.
Enables data independence, allowing changes at one level without affecting others.
Improves security by limiting user access to specific views.
