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

Compare the efficiency of the two mining processes, Consider the following ...

Consider the following database containing five transactions. Let min_sup = 60%. Mine all frequent itemsets using Apriori and FP-growth algorithm. Compare the efficiency of the t

Modelling and normalisation, Task Part A. Create an ERD from a business pro...

Task Part A. Create an ERD from a business problem. (50 marks) Read the following problem and complete the tasks listed below. THE ABS Blood Bank Australian Blood Services (ABS) i

Explain retrieval in qbe, Explain retrieval in QBE? Retrieval in QBE : ...

Explain retrieval in QBE? Retrieval in QBE : A "GUI" for expressing queries. Based on the Domain Relational Calculus (DRC) Actually invented before GUIs. Very co

What is predictive modelling, Problem: (a) Data mining is one of the b...

Problem: (a) Data mining is one of the best ways to analyse data and using software techniques, hidden and unexpected patterns and relationships in sets of data can be extrac

How can redundant associations be done, How can Redundant Associations be d...

How can Redundant Associations be done It can be done by asking questions: i)  Is there a specific arrangement of network which would optimize critical aspects of completed

Can your organization scan large format documents, Can your organization sc...

Can your organization scan large format documents? Yes, large format scanning used for such entities as city plans and blueprints is available. We selected scanners with the ab

Give an example of multiple inheritance, Give an example of multiple inheri...

Give an example of multiple inheritance.  One example of multiple inheritance is a committee for students affair which include faculty and administrative staff member.

2phase locking, we need example of 2phase locking

we need example of 2phase locking

Unix System Administration, What Command You Use What Day of the week were ...

What Command You Use What Day of the week were you born

Enforce referential integrity, Use Access 2007 to create a database calle...

Use Access 2007 to create a database called UniLib.mdb. - this file should be created on your personal drive at the university (or C: if you're using Access 2007 at home) and t

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