Module - 1
Module - 1
Module - 1
1. Physical level
It is the lowest level of abstraction for DBMSs, defining how data is
stored, data structures for storing data, and database access
mechanisms.
Developers or database application programmers decide how to
store data in the database. It is complex to understand.
2. Logical level
The logical level is the next higher level or intermediate level. It
explains what data is stored in the database and how those data are
related. It seeks to explain the complete or entire data by describing
what tables should be constructed and what the linkages between
those tables should be. It is less complex than the physical level.
3. View level
This is the top level. There are various views at the view level, with
each view defining only a portion of the total data. It also facilitates
user engagement by providing a variety of views or numerous views
of a single database. All users have access to the view level. This is
the easiest and most simple level.
Data Independence
The primary goal of data abstractions in DBMS is to obtain data
independence in order to save time and money when modifying or
altering a database.
Data independence is known as the ability to change the scheme
without impacting the programmes and applications to be rewritten.
Data is isolated from programmes so that changes to the data do not
influence the program's or application's execution.
Data Models
Object Based Data Models