List two restrictions that are applied on the modification, Database Management System

Assignment Help:

List two restrictions that are applied on the modification (updation, insertion or deletion) of base tables through view. 

Ans: The two restrictions are:

1. If a view does not consist of primary key and/or at least one of the attributes along with the NOT NULL constraint which do not have default values specified, is not updatable. This restriction is needed because if we are inserting any row in the view than all attributes not included in view of the base relation are will be denoted by the NULLs if any default value is not specified. In this type of case, if any attribute is set as NOT NULL or primary key, then it should not be NULL, and the insertion will be violating the constraints.

2. If a view defined by using grouping and/or aggregate functions, is not updatable. This restriction is also needed because, if we want to modify the base relation by view then we are not in the position to identify that tuple(s) will be modified in the group in what way.


Related Discussions:- List two restrictions that are applied on the modification

Explain the role of a database administrator, Explain the Role of a databas...

Explain the Role of a database administrator a. Defining the Schema   The DBA describes the schema which consists of the structure of the data in the application. The DBA

Explain the five levels of capability maturity models, Question 1 What is ...

Question 1 What is data mining? Write Data Mining applications Question 2 What is OLAP? Write the benefits of OLAP Question 3 What is Business Intelligence? Explai

What is the difference between primary key and a unique key, What's the dif...

What's the difference between a primary key and a unique key? Both primary key and unique key enforces uniqueness of the column on which they are explained. But by default prim

Project, write a database program for concurrency transaction in a bank

write a database program for concurrency transaction in a bank

Improved reliability, Improved Reliability: In a centralised DBMS, a server...

Improved Reliability: In a centralised DBMS, a server failure stops the operations of the DBMS. Though, a failure at single site of a DDBMS, or a failure of a communication link cr

What is catalog in dbms, What is catalog in DBMS? Catalog - A relationa...

What is catalog in DBMS? Catalog - A relational DBMS maintains information about every table and index in which it contains. A catalog is a collection of special tables that st

Fragmentation, Differentiate between horizontal & mixed horizontal fragment...

Differentiate between horizontal & mixed horizontal fragmentation?

BCA, Ask qu. Write a XML with database with book details (Book ID, Title, A...

Ask qu. Write a XML with database with book details (Book ID, Title, Author, subject, published year, language, vendor, and price).estion #Minimum 100 words accepted#

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd