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 failures of controlling events between objects, What are the f...

What are the failures of Controlling Events Between Objects  Failure Unintentional termination of system. Several possible causes: failure of system hardware, o

.DBMS, please describe the data base management with the easy example &giv...

please describe the data base management with the easy example &give the application?

Write short notes on data ware housing, Write short notes on data ware hous...

Write short notes on data ware housing? Data ware housing applications needs the transformation of data from many sources into a cohesive reliable step set of data configured a

Database design and documentation, A use case diagram giving a pictorial ov...

A use case diagram giving a pictorial overview of user requirements and brief use case descriptions. As the case study contains only an outline of a business scenario, you will als

Fragmentation-design of distributed databases, Fragmentation: It is defini...

Fragmentation: It is definite as partitioning of a relation into various fragments.Every fragment can be stored at a dissimilar site.

Explain growing phase of locking, Explain Growing Phase of locking Grow...

Explain Growing Phase of locking Growing Phase: In this phase the transaction can only obtain locks, but cannot release any lock. The transaction enters the growing phase as so

advantages of database over file system, Q.   Why would you choose a datab...

Q.   Why would you choose a database system instead of simply storing data in operating system file? Define  at a base concept in details. Sol. Advantages of Database over Fil

Describe the algorithm to draw the dependency graph, Describe the algorithm...

Describe the algorithm to draw the dependency graph?   Ans: Algorithm to draw Precedence Graph is like this: a.  For every transaction T i participating in schedule S, make

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