What is the difference between base table and view?
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Answer Posted / sunanda
Views:
1. This is one type of relation which is not a part of the
physical
database.
2. It has no direct or physical relation with the database.
3. Views can be used to provide security mechanism.
4. Modification through a view (e.g. insert update delete)
generally
not permitted
Base Relation:
1. A base relation is a relation that is not a derived relation.
2. While it can manipulate the conceptual or physical
relations stored
in the data.
3. It does not provide security.
4. Modification may be done with a base relation.
We can assign the view a name & relate it the query
expression as
Create View <View Name> as <Query Expression>
Let EMPLOYEE be the relation. We create the table EMPLOYEE
as follows:-
Create table EMPLOYEE
(Emp_No integer of null
Name char (20)
Skill chars (20)
Sal_Rate decimal (10 2)
DOB date
Address char (100) )
For a very personal or confidential matter every user is not
permitted to see the Sal_Rate of an EMPLOYEE. For such users
DBA can
create a view for example EMP_VIEW defined as:-
Create view EMP_VIEW as
(Select Emp_No Name Skill DOB Address
From EMPLOYEE)
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