Explain displaying an er schema as an er diagram, Database Management System

Assignment Help:

Explain the conventions for displaying an ER schema as an ER diagram?

An E-R Diagram scheme might describe certain constraints to that the contents of a database must conform.

Mapping Cardinalities: Express the number of entities to that another entity can be related through a relationship. For binary relationship sets among entity sets A and B, the mapping cardinality must be one of:

1. One-to-one: An entity in A is related along with at most one entity in B, and an entity in B is related with at most one entity in A.
2. One-to-many: An entity in A is related along with any number in B. An entity in B is related with at most one entity in A.
3. Many-to-one: An entity in A is related with at most one entity in B. An entity in B is associated with any number in A.
4. Many-to-many: Entities in A and B are related along with any number from each other.

The suitable mapping cardinality for a particular relationship set depends on the real world being modeled. Cardinality ratios for binary relationships are represented on ER diagram through displaying 1,M, N etc. on the diamonds.

Existence Dependencies: if the existence of entity X depends on the existence of entity Y, then X is said to be existence dependent on Y.


Related Discussions:- Explain displaying an er schema as an er diagram

Explain the dependency relationship of object oriented, Explain the depende...

Explain the dependency relationship of object oriented A dependency is a relationship which states that a change in specification of one thing can affect another thing, but n

Give the general form of sql query, Give the general form of SQL query? ...

Give the general form of SQL query? Select  A1, A2............., An From  R1, R2..............., Rm Where  P

Aims of the design project, The aims of the project are: 1. To enable th...

The aims of the project are: 1. To enable the students to undertake the detailed design of a specific plant or process 2. The design projects includes: process selection; und

Inheritance, what is relationship inheritance and attribute inheritance

what is relationship inheritance and attribute inheritance

Develop motel point of sale software, Project Description: I need a poin...

Project Description: I need a point of sale for motels. It needs to run on windows and requires being network able so that we can have more than one computer using it at once.

Explain an attributes, What are attributes? Give examples. An entity is...

What are attributes? Give examples. An entity is shown by a set of attributes. Attributes are descriptive properties possessed by every member of an entity set. Example: pos

What is assertion, What is assertion? Mention the forms available. An a...

What is assertion? Mention the forms available. An assertion is a predicate expressing a condition that we wish the database always to satisfy. Domain integrity constraints.

What are the types of indices, Normal 0 false false false ...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Skills required, wrie a report on whether a BSc n information systems devel...

wrie a report on whether a BSc n information systems develops the skills required by employers in Database administration

List two restrictions that are applied on the modification, List two restri...

List two restrictions that are applied on the modification (updation, insertion or deletion) of base tables through view.  Ans: The two restrictions are: 1. If a view

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