Weak entity, Database Management System

Assignment Help:

Entity types that do not have any key attribute, and therefore cannot be identified independently, are known as weak entity types. A weak entity can be recognized uniquely only by considering some of its attributes in conjunction with the primary key attributes of another entity, which is known as the identifying owner entity.

Usually a partial key is attached to a weak entity type that is used for unique identification of weak entities associated to a particular owner entity type. The following restrictions must hold:

  • The weak entity set and the owner entity set must participate in one to many relationship set. This relationship set is known as the identifying relationship set of the weak entity set.
  • The weak entity set necessary to have total participation in the recognized relationship.

 


Related Discussions:- Weak entity

Determine the benefits of object oriented design, Determine the benefits of...

Determine the benefits of Object oriented design OOD also gives reusability, which saves time, costs and productivity gains through direct mapping to properties of Object-Orie

Domains, A domain is a set of permissible values that can be given to an at...

A domain is a set of permissible values that can be given to an attribute. So each attribute in a table has a definite domain. Values to these attributes cannot be assigned outside

Data fragmentation-use of partial data by applications, Use of partial data...

Use of partial data by applications : In common, applications work with views rather than whole relations. Thus, it may be more appropriate to work with subsets of relations rather

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

Database Models, Benefits and Limitations od Data Models?

Benefits and Limitations od Data Models?

Note gate, i want notes on this topic

i want notes on this topic

Identify all renters who have viewed all properties, Consider the subsequen...

Consider the subsequent relations RENTER(rno, fname, lname, address, tel_no, pref_type, max_rent) VIEWING(rno, pno, date, comment) PROPERTY_FOR_RENT( pno, street, area ,city,

What is class diagram, Class Diagram A class diagram is required to su...

Class Diagram A class diagram is required to support functional necessity of system. In a static design view, class diagram is used to model vocabulary of the system, simple c

Update operations, The Update Operations : Update operations are used fo...

The Update Operations : Update operations are used for altering database values. The constraint violations faced by this operation are logically the similar as the problem faced

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