Explain three level architecture of Database

Explain three level architecture of Database
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There are following three levels or layers of DBMS architecture:

• External Level : Describes part of the database that a particular user group is interested in.

•Conceptual Level: Describes structure of the whole database for a community of users.

• Internal Level : Describes physical storage structure of the database.


External Level or View level It is the users' view of the database. This level describes that part of the database that is relevant to each user. External level is the one which is closest to the end users. This level deals with the way in which individual users view data. Individual users are given different views according to the user's requirement.


Conceptual Level or Logical level It is the community view of the database. This level describes what data is stored in the database and the relationships among the data. The middle level in the three level architecture is the conceptual level. This level contains the logical structure of the entire database as seen by the DBA. It is a complete view of the data requirements of the organization that is independent of any storage considerations. The conceptual level represents all entities, their attributes, and their relationships.


Internal level or physical level It is the physical representation of the database on the computer. This level describes how the data is stored in the database. The internal level is the one that concerns the way the data are physically stored on the hardware.

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