Introduction to Databases

Introduction to Databases

• Data refers to raw facts about people, places, events, or concepts. Data is processed to reveal meaning and becomes information.
• Information is essential for making informed decisions.
• Lack of adequate information can result in poor decision-making.
• Data is a valuable resource that requires integrity and security controls for proper management.
• Data management is a discipline that focuses on effective data generation, storage, and retrieval.

Traditional File Systems

• Traditional file systems were often used before database systems, but they presented several problems:
  • Extensive programming in third-generation language (3GL) was required to access data, making ad hoc queries impossible.
  • Data and structural dependence made changes to data or file structure difficult and time-consuming.
  • Data redundancy resulted in inconsistencies and data anomalies (modification, insertion, deletion).
• Data dependence meant that any changes to a file's data structure required modifications to the programs accessing it.
• Structural dependence meant that changes to the file structure also required changes to related programs.
• Data redundancy led to conflicting versions of the same data, resulting in data inconsistency and a lack of integrity.

Database Systems

• Database systems offer advantages over traditional file systems by providing a centralized repository for related data.
• Eliminating inconsistency, data anomalies, data dependence, and structural dependency are some of the key benefits of database systems.
• Storing data structures, relationships, and access paths in a centralized manner makes data accessible for various applications.
• The database approach encourages the use of existing data for multiple applications.

Objectives of Database Technology

• Data independence: The ability to change the logical or physical structure of data without requiring changes to application programs. This is achieved through the database catalog/dictionary (metadata) and helps to maintain consistency.
• Minimal data redundancy: Reducing the duplication of data by separating data into logical sets. Data sharing ensures that information is only stored once.
• Increased data sharing: Encouraging the simultaneous use of the same data by multiple users without creating inconsistencies.
• Improved data quality: Implementing validation rules and integrity constraints to eliminate data integrity problems.
• Improved security of data: Protecting data from unauthorized access by implementing user identification, passwords, and data encryption.
• Improved access to data: Providing easy access to data through standardized query languages and user-friendly interfaces.
• Reduced program maintenance: Minimizing the impact of changes to data structures by managing modifications to the database catalog or directory.
• Inter-relating data through a data model: Representing data structure and relationships within the database using different models (conceptual, implementation).

Database vs. File Systems

• Database systems offer a more structured and efficient approach to data management compared to traditional file systems.
• Database Management Systems (DBMS) provide a set of programs to manage database structures and regulate data access.
• DBMS functions include data dictionary management, data storage management, data transformation and presentation, security management, multi-user access control, backup and recovery management, data integrity management, database language and application programming interfaces, and database communication interfaces.

Database Models

• Data models are used to represent the logical structure of data and relationships within the database.
• Conceptual models focus on the logical nature of data representation.
• Implementation/Physical models emphasize the specific storage and retrieval of data in the database.
• Hierarchical data model: Represents data in a tree-like structure where each parent can have multiple children, but each child has only one parent.
• Network data model: Allows each record to have multiple parents. It is composed of sets, where each set has an owner record and member records. Member records can have multiple owners.
• Relational database model: The most common data model, presented to users as a collection of tables. Each table consists of rows (tuples) and columns (attributes). Tables are related by sharing common entity characteristics.

Relational Database Model Terminology

• Relation: Represented as a table in a relational database, consisting of tuples (rows) and attributes (columns).
• Tuple: A single row in a relation, representing a specific instance of data.
• Attribute: A single column in a relation, representing a specific data characteristic.

Summary

• Databases provide a more efficient and structured approach to data management than traditional file systems.
• A DBMS is a software system that implements and manages a database.
• Databases offer a centralized data repository, promoting data sharing, integrity, and security.
• Data independence, minimal redundancy, and improved data quality are key advantages of database systems.
• The relational database model is the most widely used model, providing flexibility and ease of use for users.

This quiz covers the fundamental concepts of databases, including the distinction between data and information, the importance of data management, and the limitations of traditional file systems. Understand how data integrity and security play a critical role in effective data handling. Test your knowledge on the principles that underlie the management of data.