Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
Explain the concept of generalization and aggregation in E_R diagrams. Give one example for each one of them?
Generalization: Consider extending the entity set account through classifying accounts as being either savings-account or chequing-account. Each of these is described through the attributes of account plus additional attributes. (Savings has interest-rate and cheque has overdraft-amount.) We can express the similarities among the entity sets through generalization. This is the procedure of forming containment relationships among a higher-level entity set and one or more lower-level entity sets.
Aggregation: The E-R model cannot express relationships between relationships. When would we require such a thing?
Consider a DB along with information about employees who work on a particular project and use a number of machines doing in which work. We get the E-R diagram shown in Figure.
Figure: E-R diagram with redundant relationships
Relationship sets work and uses could be combined into a single set. Therefore, they shouldn't be, as this would obscure the logical structure of this scheme. The solution is to use aggregation.• An abstraction by those relationships is treated as higher-level entities.• For our instance, we treat the relationship set work and the entity sets employee and project as a higher-level entity set called work.• Another figure shows the E-R diagram with aggregation.
Explain the cartesian product in Database Management System
Importance Of File Organisation In Database To execute a database efficiently, there are various design tradeoffs needed. One of the most vital ones is the file Organisation. F
1. Design the logic, using a looping structure, for a program that outputs every even number from 1 through 25 along with its square and cube. 2. Mr. Sanchez owns 12 apartme
You are required to program (in a high level language such as C, C++, Java) and implement a cache simulator which will have the following inputs and outputs:- INPUTS
I need help for my Uni assignments
Introductory course and so does not require any fancy coding. I will provide a guidance document to help you in producing the solutions.
Group By clauses • It is used to group database tuples on the basis of definite common attribute value like as employees of a department. WHERE clause still can be used
Use inheritance as an implementation technique when you are going to use inheritance as an implementation technique, you can achieve same goal in a safer way by making one cla
(a) Differentiate between information and data . (b) List and briefly explain five potential benefits of the database approach compared to conventional file systems. (c) Diff
Objectives After reading this unit you should be able to: Explain storage of databases on hard disks; Discuss the execution of various file Organisation techniques;
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!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd