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

Need for distributed database systems, Need For Distributed Database System...

Need For Distributed Database Systems A distributed database is a set of database kept on multiple computers that appears to applications as a one database. As a result, an app

Advantages of Observation Methods, Advantages of Observation  Methods: ...

Advantages of Observation  Methods: Bailey has pointed  out four  advantages of observation: 1. Superior in Data  Collection  on Non Verbal Behavior: When  a person  a opi

Security-data fragmentation, Security: Data not needed by local applicatio...

Security: Data not needed by local applications is not stored at the site, therefore no unnecessary security violations may exist. But how can we carry out fragmentation? Fragm

Describe the association - design, Describe the Association: Design  ...

Describe the Association: Design  Before we describe association design let us define association "Association is set of links between two objects in the object model". It is

Explain the disadvantages of creating a temporary table, Explain the disadv...

Explain the disadvantages of creating a temporary table? If you have already created a temporary table with a shown name and attempting to create a second one with that nam

Explain transaction manager and their work, Explain Transaction manager and...

Explain Transaction manager and their work? Transaction Manager: Ensure the database remains in a constant (correct) state despite system failure, and in which concurrent trans

What is a super key, What is a super key? A super key is a set of one o...

What is a super key? A super key is a set of one or more attributes that collectively permits us to recognize uniquely an entity in the entity set.

Define granularity and hierarchy of granularity of locks, Define granularit...

Define granularity, hierarchy of granularity of locks & multiple granularity locking. Explain the modified two phase locking along with multiple granularity locking. Ans: The s

Case study, what problems are raised by the database? why is it so controve...

what problems are raised by the database? why is it so controversial? why is data quality an issue?

What is a candidate key, What is a candidate key? Minimal super keys ar...

What is a candidate key? Minimal super keys are known as candidate keys.

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