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

What are the states of transaction, What are the states of transaction? ...

What are the states of transaction? The states of transaction are:- a) Active b) Partially committed c) Failed d) Aborted e )Committed   f) Terminated

Explain the three data anomalies, What are the three data anomalies that ar...

What are the three data anomalies that are similarly to take place as a result of data redundancy?  Can data redundancy be completely eliminated in database approach?  Why or why n

State about the use case diagram, State about the Use Case Diagram A u...

State about the Use Case Diagram A use case diagram represents a set of use cases, actors and their relationships. These diagrams shall be used to model context or requirement

Draw an entity-relationship model, Draw an Entity-Relationship model for ...

Draw an Entity-Relationship model for the relational schema given in the Appendix. Show all the entities, relationships, relationship names, and attributes and also underline the

MULTI-LIST FILE ORGANIZATION, sir, could anybody help me in getting complet...

sir, could anybody help me in getting complete information about the mentioned topic

Optimistic concurrency control, Optimistic Concurrency Control Is locki...

Optimistic Concurrency Control Is locking the only way to stop concurrency related problems? There exist some other ways too. One such way is known as an Optimistic Concurrency

Define network dbms, Define Network DBMS The NDBMS is built primarily o...

Define Network DBMS The NDBMS is built primarily on a one-to-many relationship, but where a parent-child representation between the data items cannot be ensured. This may occur

ER Diagram, A database will be made to store information about patients in ...

A database will be made to store information about patients in a hospital. On arrival, each patient’s personal details (name, address, and telephone number) are recorded where poss

Creating views with read only option-data control, Creating views with Read...

Creating views with Read only option : In the view definition this option is used to make sure that no DML operations can be done on the view.

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