three-schema architecture

The three-schema architecture is a way to organize database systems into three layers to improve flexibility and manageability. The **internal schema** handles how data is physically stored on hardware, like locations and file structures. The **conceptual schema** defines what data is stored, its structure, and relationships, serving as a community-wide blueprint. The **external schema** comprises different user views, showing only relevant parts of the data depending on user needs. This separation allows changes in physical storage or user interfaces without affecting the overall data structure, making databases more adaptable and easier to maintain.