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

What is meant by log-based recovery, What is meant by log-based recovery? ...

What is meant by log-based recovery? The most widely used structures for recording database changes is the log. The log is a sequence of log records, recording all the update a

Calculate the record size r in bytes, An employee record has the following ...

An employee record has the following structure struct employee { int eno; char name[22]; float salary; char dept[10];}; (i) Calculate the record size R in bytes.

Project, Preliminary entities and attributes of human resourse management d...

Preliminary entities and attributes of human resourse management database management system

Availability-data replication, Availability: A site having the copy of a r...

Availability: A site having the copy of a replicated relation fails, even then the relation may be found in another site. Therefore, the system may carry on to process at least th

What is disadvantages of dbms, What is Disadvantages Of DBMS ? 1. Cos...

What is Disadvantages Of DBMS ? 1. Cost of Software and Hardware and Migration - A important disadvantage of the DBMS system is cost. 2. Reduced Response and Throughpu

Candidate keys, Super keys of a relation can have extra attributes. Candida...

Super keys of a relation can have extra attributes. Candidate keys are minimal super key, i.e. such a key have no extraneous attribute. An attribute is known as extraneous if even

Explain different addressing modes of 8086, 1. Explain different addressing...

1. Explain different addressing modes of 8086 Explanation of all addressing modes 2. Write a sequence of instructions to exchange two register contents using stack

#title using the invoice, using the invoice table shown below,write the rel...

using the invoice table shown below,write the relational schema,draw a dependencies,inclunding all partial and transitive dependencies.assume that the table does not contain repeat

Explain data dictonary on oracle, Explain data dictonary on oracle ? Da...

Explain data dictonary on oracle ? Data Dictionary - Data dictionaries are the system tables in which contain descriptions of the database objects and how they are structured.

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