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

Write query to select student from math department, Consider the table stud...

Consider the table student and list names of students in the departments other than maths and computer. SELECT std_name FRM student WHERE dept_name NOT IN (‘Maths','Computer);

Write expressions in relational algebra, Given the subsequent relations: ...

Given the subsequent relations:    vehicle (reg_no, make, colour)    Person (eno, name, address)    Owner (eno, reg_no)   Write expressions

Define the terms entity, Define the terms entity, attribute, role and relat...

Define the terms entity, attribute, role and relationship between the entities, giving examples for each of them.         Ans: Entity:   An entity is a "thing" or "object" in th

Heterogeneous ddb and homogeneous ddb, Probelm: (a) A distributed datab...

Probelm: (a) A distributed database (DDB) is a collection of multiple, logically interrelated databases which are physically distributed over a computer network" (i) Give a

The data of a view is not physically stored, The data of a view is not phys...

The data of a view is not physically stored, but derived from one or more tables. True the data of a view is not physically stored

What is meant by object identifiers, What is meant by object identifiers? ...

What is meant by object identifiers? Object-oriented systems use an object identifier to recognize objects. Object identifiers are unique: that is every object has a single ide

Shadow paging, Describe the shadow paging technique.

Describe the shadow paging technique.

Define multivalued dependency, Define multivalued dependency.  What do unde...

Define multivalued dependency.  What do understand by trivial multivalued dependency?  Ans: A multivalued dependency is a full constraint among two sets of attributes in a rela

Define ssn of salesman by using database of business trips, Consider the su...

Consider the subsequent relations for a database which keeps track of business trips of salespersons in a sales office: SALESPERSON (SSN, Name, start_year, Dept_no) TRIP (SSN, Fr

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