DBMS | Three-Schema Architecture
What is Three-Schema Architecture in DBMS?
- The three schema architecture is also called ANSI / SPARC architecture or three-level architecture.
- The three schema architecture is used to separate the user applications and the physical database.
- This framework is used to describe the structure of a specific database system.
The three schema architecture is divided into three levels.
- Internal (Physical) level
- Conceptual (Logical) level
- External level (End-user)
Internal (physical) level / schema
The internal schema defines the physical storage structure of the database. And what are the data stored in the database, what is its size, what is its location, and in which file it is stored, all this information is on the physical level? The internal schema is a low-level representation of the entire database. In ANSI terms, it is also called a "stored record".
Conceptual (logical) level / schema
The conceptual schema describes the database structure of the entire database for the users. This schema hides information about physical storage structures and focuses on data types, relationships, entities, etc. That is, in this level, what data will be stored in the database, in what format will the data be stored, what will be the size of the data, and what will be the relation between that data, all these are information. Programmers and database administrators are working on such a level.
External (user view) level / schema
External or View Level contains the same data which is of use to the user, the activity happening in the back-end does not make any sense to the user. Font-end designers work in this level and use HTML, and CSS to decide how to show data to the user.
For example, whenever the user logs in after entering the user name and password to access an application or site, then the interface that comes in front of the user after logging in is called Interface, External or View Level.
