Database Management Concepts

This book is a detailed introduction to Database Management Systems (DBMS) with a strong focus on both theory and practical SQL usage. It is organized like a textbook, moving from basic database concepts to advanced topics such as ER modeling, relational algebra, SQL, normalization, transaction management, concurrency control, and recovery. The style is educational and exam-oriented, with many examples, definitions, diagrams, and practice questions. The opening chapter explains what a database is, why DBMS is needed, and how it improves over file systems. It highlights the main problems of file-based processing, including redundancy, inconsistency, difficult data access, security issues, and atomicity problems. The second chapter covers the Entity-Relationship (ER) model in depth. It explains entities, attributes, keys, weak and strong entity sets, relationship sets, cardinality, participation constraints, and extended ER features such as specialization, generalization, and aggregation. The third chapter introduces the relational model and relational algebra. It explains how tables, tuples, attributes, domains, and keys work in a relational database.