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.
You are required to write a report which evaluates two of the following issues in relation to your case study database: a. Security issues b. Performance issues c. Backup
Load sample data into the database tables design and test queries to return the following information • All rows and columns for employees • All rows and columns for customers •
Explain current page table and shadow page table. The key idea behind the shadow paging method is to maintain two page tables during the life of the transaction: the current pa
Question 1: Define the term business intelligence tools? Briefly explain how the data from one end gets transformed into information at the other end? Definition Exp
Benefits of using heuristics
cardnality ratio for humanresource mangement system
composite attribute
what is database management system? & why it is required?
Normal 0 false false false EN-US X-NONE X-NONE
Illustrate the view of software architecture A model is a semantically closed abstraction of system composes of elements. It can be visualized using any of the following five v
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: +1-415-670-9521
Phone: +1-415-670-9521
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd