What are the various symbols used to draw an e-r diagram, Database Management System

Assignment Help:

What are the various symbols used to draw an E-R diagram? Explain with the help of an example how weak entity sets are represented in an E-R diagram.

Various symbols used to draw an E-R diagram

13_Symbol ER Diagram.png


Weak Entity Sets - An entity set that does not have a key attribute is called weak entity set. A weak entity must participate in an identifying relationship type with an owner or identifying entity type Entities are identified by the combination of:
• A partial key of the weak entity type
• The primary key of the identifying entity type

Example:
Suppose that a DEPENDENT entity is identified by the dependent's first name and birhtdate, and the specific EMPLOYEE that the dependent is related to. DEPENDENT is a weak entity type with EMPLOYEE as its identifying entity type via the identifying relationship type DEPENDENT_OF

1958_Dependents.png


Related Discussions:- What are the various symbols used to draw an e-r diagram

Entity integrity constraint - relational constraints, It defines that no pr...

It defines that no primary key value can be null. This is as the primary key is used to recognize individual tuple in the relation. So we will not be able to recognize the records

Define the term- state, State The position of object at any moment is ...

State The position of object at any moment is called state. An object can have many states depend upon time. After receiving some input instructions, the object can change its

Fds in relationships and teaches relationship, FDs in Relationships:  E...

FDs in Relationships:  Enrols Relationship: None as it is many to many Teaches Relationship : Course code → Instructor Instructor → Course code The next question is:

Query optimization in database system, Problem : AirwaysCentre, an inte...

Problem : AirwaysCentre, an international airline booking company currently uses a relational database system for their operations, which includes the following relations: P

Normalization, Normalize the given relation to 3NF, justifying each step

Normalize the given relation to 3NF, justifying each step

Explain what is to be done during defining problem statement, Briefly expla...

Briefly explain what is to be done during defining problem statement. To define Problem Statement of a system, define what is to be done and how you can go to implement that. Y

What is deadlock, What is deadlock? Neither of the transaction can ever...

What is deadlock? Neither of the transaction can ever proceed with its normal implementation. This situation is known as deadlock.

Define physical and logical data independence, Define physical and logical ...

Define physical and logical data independence. How does this architecture help in achieving these? Data independence entails that change in one view must not need a change in t

Illustrate the class diagram for class room scheduling, Illustrate the clas...

Illustrate the class diagram for class room scheduling system If in any college, the number of classrooms are limited which have to be allocated to various classes and instruct

Data control, Identify the need and use of data control through problem sol...

Identify the need and use of data control through problem solving, illustration

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