Database Management Systems
UNIT – I
1.1 Introduction
Data:
• A collection of raw facts and information.
• Any recorded fact with implicit meaning is considered data.
Database:
• A collection of interrelated data stored in tables.
• Can vary in size and complexity.
• Can be manually or computerized.
• Example: A Customer Database may include fields like cname, cno, and ccity.
Database Management System (DBMS):
• A software system that allows users to create, maintain, and manipulate databases.
• Provides tools for defining, constructing, and managing databases for various
applications.
1.2 Database-System Applications
Databases are essential across various domains. Some key applications include:
a) Enterprise Information
• Sales: Manages customer, product, and purchase details.
• Accounting: Tracks payments, receipts, balances, and assets.
• Human Resources: Stores employee details, salaries, payroll, and benefits.
• Manufacturing: Manages supply chains, production, and inventory.
• Online Retailers: Handles sales, order tracking, recommendations, and product reviews.
b) Banking and Finance
• Banking: Manages customer accounts, loans, and transactions.
• Credit Card Transactions: Stores purchase history and generates statements.
• Finance: Tracks stock holdings, sales, purchases, and real-time market data.
c) Universities
• Maintains student records, course registrations, and grades.
, • Includes standard enterprise functions like human resources and accounting.
d) Airlines
• Manages reservations and schedules.
• Among the first industries to use geographically distributed databases.
e) Telecommunication
• Keeps records of calls, generates bills, maintains prepaid balances, and manages
network data.
1.3 Purpose of Database Systems
Earlier database applications relied on file systems, leading to several issues:
1. Data Redundancy and Inconsistency
• Storing data in multiple file formats caused duplication and inconsistency.
2. Difficulty in Data Access
• New programs were needed for each query or task.
3. Data Isolation
• Information was scattered across multiple files and formats.
4. Integrity Problems
• Constraints (e.g., account balance > 0) were embedded in program code, making updates
difficult.
5. Atomicity of Updates
• Failures could leave the database in an inconsistent state.
• Example: A fund transfer should either complete fully or not happen at all.
6. Concurrent Access Issues
• Multiple users accessing data simultaneously could cause inconsistencies.
• Example: Two users withdrawing money at the same time might lead to incorrect balance
updates.
UNIT – I
1.1 Introduction
Data:
• A collection of raw facts and information.
• Any recorded fact with implicit meaning is considered data.
Database:
• A collection of interrelated data stored in tables.
• Can vary in size and complexity.
• Can be manually or computerized.
• Example: A Customer Database may include fields like cname, cno, and ccity.
Database Management System (DBMS):
• A software system that allows users to create, maintain, and manipulate databases.
• Provides tools for defining, constructing, and managing databases for various
applications.
1.2 Database-System Applications
Databases are essential across various domains. Some key applications include:
a) Enterprise Information
• Sales: Manages customer, product, and purchase details.
• Accounting: Tracks payments, receipts, balances, and assets.
• Human Resources: Stores employee details, salaries, payroll, and benefits.
• Manufacturing: Manages supply chains, production, and inventory.
• Online Retailers: Handles sales, order tracking, recommendations, and product reviews.
b) Banking and Finance
• Banking: Manages customer accounts, loans, and transactions.
• Credit Card Transactions: Stores purchase history and generates statements.
• Finance: Tracks stock holdings, sales, purchases, and real-time market data.
c) Universities
• Maintains student records, course registrations, and grades.
, • Includes standard enterprise functions like human resources and accounting.
d) Airlines
• Manages reservations and schedules.
• Among the first industries to use geographically distributed databases.
e) Telecommunication
• Keeps records of calls, generates bills, maintains prepaid balances, and manages
network data.
1.3 Purpose of Database Systems
Earlier database applications relied on file systems, leading to several issues:
1. Data Redundancy and Inconsistency
• Storing data in multiple file formats caused duplication and inconsistency.
2. Difficulty in Data Access
• New programs were needed for each query or task.
3. Data Isolation
• Information was scattered across multiple files and formats.
4. Integrity Problems
• Constraints (e.g., account balance > 0) were embedded in program code, making updates
difficult.
5. Atomicity of Updates
• Failures could leave the database in an inconsistent state.
• Example: A fund transfer should either complete fully or not happen at all.
6. Concurrent Access Issues
• Multiple users accessing data simultaneously could cause inconsistencies.
• Example: Two users withdrawing money at the same time might lead to incorrect balance
updates.
