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

Prepare an erd for the scenario, Question: (a) Prepare an ERD for the s...

Question: (a) Prepare an ERD for the scenario given below. (b) Convert the ER diagram produced in (a) above into its physical design. You have to choose an appropriate Pri

Differentiate between a global and a local temporary table, Differentiate b...

Differentiate between a Global and a Local temporary table? - A local temporary table exists only for the duration of a connection or if defined inside a compound statement, fo

Determine the programming language structures, What is the most significant...

What is the most significant feature that does not directly map into programming language structures? Why? Association, since there are complex types of association, like as qu

Explain the two types of participation constraint, Explain the two types of...

Explain the two types of participation constraint.  Total: The participation of an entity set E in a relationship set R is said to be total if each entity in E participates i

Database models, why are older data models are being replaced by new data m...

why are older data models are being replaced by new data models

What is a hashing function, What is a hashing function?  What are the prope...

What is a hashing function?  What are the properties of a good hashing function?  Describe the folding technique for hashing functions.      Ans:  Hashing function is a method

Data warehouse, 1) Define a job scheduling strategy that will meet business...

1) Define a job scheduling strategy that will meet business requirement of reporting availability by 6am CST for the following cubes? Show the job scheduling dependencies in a pict

What is rdbms, What is RDBMS? Relational Data Base Management Systems (...

What is RDBMS? Relational Data Base Management Systems (RDBMS) are database management systems that maintain data records and indices in tables. Relationships may be formed and

Sequential file organisation, Sequential File Organisation The most nec...

Sequential File Organisation The most necessary way to organise the collection of records in a file is to use sequential Organisation. Records of the file are stored in series

What are the ways of obtaining the connection parameters, What are the ways...

What are the ways of obtaining the connection parameters?  Hardwire the parameters into the program. Ask for the parameters interactively. Get the parameters

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