Easy DBMS Aptitude Questions 2008
(Part - 2)
What is Data Independence in DBMS?
independence means that "the application is independent of the storage
structure & access strategy of data". In other words, The ability to
modify the schema definition in one level should not affect the schema
definition in the next higher level.
types of Data Independence:
in physical level should not affect the logical level.
Modification in logical level should affect the view level.
Data Independence is more difficult to achieve
What is a view in DBMS? How it is related to data independence?
view may be thought of as a virtual table, that is, a table that does not really
exist in its own right but is instead derived from one or more underlying base
table. In other words, there is no stored file that direct represents the view
instead a definition of view is stored in data dictionary. Growth &
restructuring of base tables is not reflected in views. Thus the view 136 can
insulate users from the effects of restructuring & growth in the database.
Hence accounts for logical data independence.
3. What is Data Model in DBMS?
collection of conceptual tools for describing data, data relationships data
semantics & constraints.
4. What is E-R model?
data model is based on real world that consists of basic objects called entities
& of relationship among these objects. Entities are described in a database
by a set of attributes.
5. What is Object Oriented model?
model is based on collection of objects. An object contains values stored in
instance variables with in the object. An object also contains bodies of code
that operate on the object. These bodies of code are called methods. Objects
that contain same types of values & the same methods are grouped together