Data Modelling

Schemas

A schema is an overall description of a database, and it is usually represented by the entity relationship diagram (ERD). There are many subschemas that represent external models and thus display external views of the data. Below is a list of items to consider during the design process of a database.

• External schemas: there are multiple
• Multiple subschemas: these display multiple external views of the data
• Conceptual schema: there is only one. This schema includes data items, relationships and constraints, all represented in an ERD.
• Physical schema: there is only one