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

Cartisian product, Explain the cartesian product in Database Management Sys...

Explain the cartesian product in Database Management System

Explain the static or conservative two phase locking, Explain the Static or...

Explain the Static or conservative Two Phase Locking: Static (or conservative) Two Phase Locking: In this type of scheme, all the data items are locked earlier than any opera

Express the ways provided by mysql for pattern matching, Express the ways p...

Express the ways provided by MySQL for Pattern Matching? MySQL provides two kinds of pattern matching. 1) One is based on SQL patterns 2) Regular expressions.

List the types of authorization, List the types of authorization. A) R...

List the types of authorization. A) Read authorization B) Write authorization C) Update authorization D) Drop authorization

What do you mean through integrity constraints, What do you mean through in...

What do you mean through integrity constraints? Integrity Constraints -An integrity constraint is a condition specified on a database schema and restricts the data in which

What is trigger, What is trigger?  Triggers are statements that are exe...

What is trigger?  Triggers are statements that are executed automatically by the system as the side effect of a modification to the database.

How can you map null values to other values while display, How can you map ...

How can you map NULL values to other values while display? IF( ) , IFNULL( ) keywords are used to do so. They are 'LIMIT' is used for the following kinds of problems: 1) Ans

Disadvantages or unsecure, In Database software have only pure security or ...

In Database software have only pure security or some dis secured by administrator?

What are metrics for choosing the best algorithm, What are metrics for choo...

What are metrics for choosing the best algorithm? Matrices for choosing the best algorithms are as below: Computational complexity Ease of understand ability and im

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