three schema architecture in dbms | 3 schema architecture | three level architecture of dbms

Опубликовано: 02 Декабрь 2019
на канале: QuickCS
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Three schema architecture in dbms: Three level architecture.
What are we going to learn?
Reason of creation of 3 schema architecture.
What is three schema architecture?
Why is 3 schema architecture created?
Three schema architecture was created to keep the physical database separate from the user applications.
What is 3 schema architecture?
In 3 schema architecture, the schemas can be divided into 3 levels.
The internal level
The conceptual level
The external level or view level
1. The internal level
The internal level has an internal schema, that describes the physical storage structure of the database.
The internal schema uses a physical data model to describe the complete details of data storage and access paths for the database.
2. The conceptual level
The conceptual level has a conceptual schema, which describes the structure of the whole database for a community of users.
The conceptual schema hides the details of physical storage structures and concentrates on describing entities, data types, relationships, user operations, and constraints.
3. The external level
Basically external level has different external views for different users.
Each external schema or external view, describes the specific part, that the specific user group is interested in and hides rest of the database, for that user group.
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