1.

Illustrate the difference between the three levels of data abstraction.

Answer»
Internal LevelConceptual Level External Level
Describes how the data is actually stored on the storage medium.Describes what data are actually stored in the database and relationship existing among data. Concerned with the data is viewed by individual users. At this level, complex low-level data structure are described in details. Concerned with the data is viewed by individual users.
At this level, complex low-level data structure are described in details.At this level, the database is described logically in terms of simple data-structures.Only a part of the database relevant to the users is provided to them through this level.


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