Three Schema Architecture Overview
📌 The Three Schema Architecture is designed to separate user applications from the physical database structure, operating across three levels: internal, conceptual, and external.
💾 The internal level defines the physical storage structure using low-level/physical data models, detailing how data is stored and defining access paths.
🌐 The conceptual level describes the overall structure of the database (entities, relationships, attributes), hiding physical storage details.
🧑‍💻 The external level comprises multiple external schemas or views, each detailing only the part of the database relevant to a specific user group.

Data Independence Concept
✨ Data independence is the capacity to modify a schema at one level without needing to change the schema at the next higher level.
🔄 When changes occur, only the mapping between the affected levels needs updating, preserving the integrity of higher-level schemas or applications.

Types of Data Independence
🔗 Logical Data Independence operates between the conceptual schema and the external schema (user views/applications).
➕ This allows modifications to the conceptual schema (e.g., adding a new attribute) without requiring changes to external schemas or application programs.
⚡ Physical Data Independence operates between the internal schema and the conceptual schema.
🛠️ This allows modifications to the internal schema (e.g., changing file location or access paths) to improve performance without affecting the conceptual schema, provided the stored data remains the same.

Key Points & Insights
➡️ The DBMS handles transformation of user requests specified in the external schema, sending them sequentially to the conceptual and then the internal schema for processing.
➡️ The process of transforming requests and results between the three levels (internal, conceptual, external) is known as mapping.
➡️ The primary benefit of the three-schema approach is achieving data independence, crucial for system flexibility and maintenance.

📸 Video summarized with SummaryTube.com on Dec 12, 2025, 17:20 UTC