Introduction to DBMS

Introduction to DBMS

• A Database Management System (DBMS) is a software system enabling users to define, create, and manage a database.
• It provides a structured method for storing, retrieving, and manipulating data.
• DBMSs manage complex data operations, security, and access controls.
• Examples include MySQL, PostgreSQL, Oracle, and SQL Server.

Key Features of DBMS

• Data Definition Language (DDL): Defines the database structure (tables, constraints).
• Data Manipulation Language (DML): Interacts with database data (insert, update, delete, select).
• Data Query Language (DQL): A specific DML for querying data.
• Data Control Language (DCL): Controls data access (permissions, security).
• Transaction Management: Handles concurrent data access with ACID properties (Atomicity, Consistency, Isolation, Durability).
• Security: Manages user authentication, authorization, and access control.
• Data Integrity: Ensures data accuracy and consistency using constraints and rules.
• Data Recovery: Restores data from backups post-failure.

Database Models

• Relational Model: Most common; data in tables with rows and columns, relationships via keys.
• Hierarchical Model: Data structured like a tree with parent-child relationships.
• Network Model: More complex relationships than hierarchical, represented as a graph.
• Object-Oriented Model: Treats data and relationships as objects, allowing complex data structures.
• NoSQL Models: Non-relational models like key-value stores, document databases, graph databases, and column-family stores for very large, complex datasets.

Advantages of Using DBMS

• Data Integrity: Maintains data consistency and accuracy through constraints.
• Data Security: Controls access and protects from unauthorized use.
• Data Sharing: Enables concurrent data access and sharing.
• Data Independence: Separates data from applications; easier to modify database structure.
• Data Efficiency: Improves data storage and retrieval.
• Data Consistency: Ensures data accuracy using constraints.

Components of DBMS

• Database Engine: Manages data storage, retrieval, and manipulation.
• Data Dictionary: Defines the database structure (metadata).
• Query Processor: Evaluates and executes user queries.
• User Interface: Provides tools for database interaction (e.g., graphical, command-line).
• Application Programs: Allow users to interact with the database.

Types of DBMS Users

• DBA (Database Administrator): Manages installation, configuration, backups, and restorations.
• Application Developers: Develop applications that interact with the database.
• End Users: Access the database using applications.

Data Normalization

• Organizes database data to reduce redundancy and improve integrity.
• Prevents insertion, update, and deletion anomalies.
• Involves multiple normalization levels (e.g., 1NF, 2NF, 3NF).

SQL (Structured Query Language)

• Standard language for interacting with relational databases.
• Used for querying, updating, and managing database data.
• Basic commands include SELECT, INSERT, UPDATE, DELETE.

ACID Properties

• Atomicity: All operations within a transaction are treated as a single unit.
• Consistency: Transactions change the database from one valid state to another.
• Isolation: Concurrent transactions execute without interfering with each other.
• Durability: Committed transaction changes are permanent, surviving failures.