The goal of Three-Schema architecture is to separate the user applications and physical database. In this architecture, schemas can be defined at the following three levels:

• The internal level:- The internal level has an internal schema which describes the physical storage structure of the database.


• The conceptual level:-The conceptual level has a conceptual schema, it describes the entities, data types, relationships, user operations, and constraints.


• The external level or view level:- The external or view level includes a number of external schemas or user views. It describes the part of the database that a particular user group is interested in and hides the rest of the database from that user group.