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.
Synonyms and Indexes Some of the essential properties of indexes are: An Index is a schema Object Indexes can be formed explicitly or automatically Indexes are m
What are the states of transaction? The states of transaction are:- a) Active b) Partially committed c) Failed d) Aborted e )Committed f) Terminated
Question: a) What is Client/Server and what benefits can be expected from Client/Server systems? b) Explain what middleware is and what it does. Why would MIS managers be p
Explain the Strategy of Database Planning ?
What are the two types of blocks in the fixed -length representation? Define them. Anchor block: Have the first record of a chain. Overflow block: Have the records other tha
The domain that you will model in this assignment is that of courses and students at a university. So as not to make the task too large and unspecified, you will here get a descrip
What are the benefits of decomposing a system? The benefits of decomposing a system into subsystems are that after decomposition, each individual component become smaller and e
wh
When is a transaction rolled back? Any changes that the aborted transaction made to the database must be uncompleted. While the changes caused by an aborted transaction have be
Data Scrubbing 70,000 records Project Description: We need services of a developer competent in data cleansing/Data scrubbing. Scope: - 70,000 records in CSV format.
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