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

Deadlock prevention, Deadlock Prevention One of the easiest approaches ...

Deadlock Prevention One of the easiest approaches for avoiding a deadlock would be to obtain all the locks at the begin of the transaction. Though, this approach restricts conc

What is a view in sql and when can views be updated, What is a view in SQL?...

What is a view in SQL? When can views be updated? A view is a virtual table which consists of columns from one or more tables. Through it is same to a table; it is stored in

Search the salary of employees who are not ‘analyst’ , Example- Search the ...

Example- Search the salary of employees who are not 'ANALYST' but get a salary below than or equal to any people employed as 'ANALYST'. SELECT EMPNO, ENAME, JOB, SAL FROMEMP

Data models, After going by the database architecture, let us now dwell on ...

After going by the database architecture, let us now dwell on an important query: how is the data organised in a database? There are a lot of basic structures that exist in a datab

Data modelling and normalization methodology, MOSS VALE is a town with 1500...

MOSS VALE is a town with 15000 inhabitants. The fire department wishes to develop a system that automates the despatch of fire engines to attend fires. The ERD below describes the

Describe log based recovery, Describe log based recovery The most usabl...

Describe log based recovery The most usably structure for recording data base modification is the LOG the log is a sequence of log records recording all the update activities i

What is the function of sql server agent windows service, What is the funct...

What is the function of SQL Server Agent Windows service? - It's a Windows service that handles tasks scheduled within SQL Server environment. These tasks are also known as job

Create student db and perform delete operation, Create Student DB and perfo...

Create Student DB and perform delete operation? STUDENT (name, student#, class, major) COURSE (course name, course#, credit hours, department) SECTION (section identifier, co

What is the use of group by clause, What is the use of group by clause?  ...

What is the use of group by clause?  Group  by  clause  is  used to apply  aggregate  functions  to a  set  of  tuples. The attributes given in the group by clause are used to

Two types of blocks in the fixed -length representation, What are the two t...

What are the two types of blocks in the fixed -length representation? Define them. Anchor block: Have the first record of a chain. Overflow block: Have the records other tha

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