Introduction to Databases and DBMS

Basic Definitions

• A database is a collection of related data.
• Data is known facts with implicit meaning.
• Metadata is data that describes other data.
• A mini-world is a specific part of the real world with data stored in a database (e.g., student grades at a university).

File-Based System vs. Database Approach

• File-based systems were early attempts to computerize manual filing systems.
• Each file in a file-based system is independent and called a flat file.
• Flat files lack structured interrelationships.
• File-based systems have limitations like data redundancy, inconsistency, program-data dependence, limited data sharing, lengthy development times, higher maintenance costs, low data security, and poor real-world modelling.

Database Approach

• The database approach overcomes the limitations of file-based systems.
• A database is a collection of similar records with relationships between them.
• A Database Management System (DBMS) is software that manages the database.
• Examples of DBMS include Oracle, SQL Server, and MySQL.
• A database system includes the DBMS software, data, and sometimes applications.

Advantages of the Database Approach

• Control of data redundancy: Minimizes data duplication.
• Program-data independence: Separates data definition from applications.
• Improved data sharing: Centralized data ownership and access for the organization.
• Data consistency: Reduces inconsistencies by controlling redundancy.
• Increased application development productivity: Streamlines development.
• Enforcement of standards: Provides consistency and standardization.
• Improved data accessibility and responsiveness: Integration and query languages like SQL enhance access.
• Improved security: Enhances data protection.

Disadvantages of the Database Approach

• Upfront costs: Installation, management, and conversion expenses can be high.
• Ongoing costs: Requires specialized personnel, backup, and recovery management.

Functions of a DBMS

• Data Dictionary Management: Stores definitions of data elements and their relationships (metadata).
• Data Storage Management: Stores data, entry forms, report definitions, validation rules, procedural code, and multimedia formats.
• Data Transformation and Presentation: Processes data into required structures.
• Security Management: Controls access through usernames, passwords, and restrictions.
• Multiuser Access Control: Enables simultaneous access while maintaining integrity.
• Backup and Recovery Management: Protects data integrity and restores databases.
• Data Integrity Management: Enforces rules to reduce redundancy and ensure consistency.
• Database Access Languages and Application Programming Interfaces: Provides non-procedural languages like SQL for querying.
• Database Communication Interfaces: Enables access from different network environments, including the internet.

Example of a Database

• A UNIVERSITY database, incorporating entities like STUDENTS, COURSES, SECTIONS, DEPARTMENTS, and INSTRUCTORS.
• Relationships include:
  • SECTIONS belong to specific COURSES.
  • STUDENTS take SECTIONS.
  • COURSES have prerequisites.
  • INSTRUCTORS teach SECTIONS.
  • COURSES are offered by DEPARTMENTS.
  • STUDENTS major in DEPARTMENTS.

Characteristics of the Database Approach

• Self-describing nature:
  • DBMS catalogs store database descriptions (metadata), enabling the DBMS to work with different applications.
• Insulation between programs and data:
  • Program-data independence allows changing data structures without modifying access programs.
• Data Abstraction:
  • Data models hide storage details and provide a conceptual view of the database.
• Support of multiple views:
  • Users can access different views of the database relevant to their needs.
• Sharing of data and multi-user transaction processing:
  • Concurrent users can access the database.
  • Concurrency control ensures correct transaction execution or abortion.
  • Recovery subsystems guarantee permanent recording of completed transactions.
  • OLTP (Online Transaction Processing) is vital in database applications.

Explore the fundamental concepts of databases, including definitions of key terms like data, metadata, and mini-worlds. Learn about the differences between file-based systems and the advantages of the database approach. This quiz provides a comprehensive understanding of Database Management Systems (DBMS).