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!
Saving Derived Attributes to Avoid Re-computation
As discussed, "redundancy means duplication of exact data". But, if multiple copies of same data are present in the system, then it can increase chance of availability of data, but the problem of computing overhead is also associated with it.
To overcome this difficulty we can "cache" or store the redundant data in its computed form and classes or objects might be defined to retain this information. The class which contains cached data must be updated if any of objects that it depends on are changed.
Figure shows use of derived object and derived attribute in OMTool. Each class box contains an ordered list of operations and attributes, each represented as text string (left of diagram). Given the location of the class box itself, the location of each attribute can be computed by adding up the size of all the elements in front of it. Since location of each element is required frequently, location of each attribute string is computed and then stored. The region containing entire attribute list is also computed and saved. In this way, you can avoid the testing of input points against the attribute text element. It is shown in the right side in Figures. If a new attribute string is added to list, then locations of the ones after it in list are simply offset by size of the new element.
Figure: Derived attribute to avoid re-computation
Question 1 Discuss the classification of DBMS based on location of database Question 2 Explain with examples different SQL commands used for creating and deleting relations.
Example -Find the employee name, salary, department number and average salary of his/her department, for those employees whose salary is more than the average salary of that depart
What are referential integrity constraints? A value that appears in single relation for a given set of attributes also appears for a particular set of attributes in another rel
Assigning Responsibility for Operation Many operations might have obvious target objects, but some of these operations could be used at numerous places in an algorithm, by one
Explain what is Aggregation ? Aggregation: This is used whenever we intend to show a relationship between an entity and the relationship. There is no provision for this in th
Mention the purpose of SID and SOD lines SID (Serial input data line): It is an input line by which the microprocessor accepts serial data. SOD (Serial output data line)
Derived horizontal fragmentation: Some applications may include a join of two or more relations. If the relations are stored at dissimilar locations, there may be a major overhead
E-R Model This data model is based on real world that consists of basic objects named entities and of relationship among these objects. Entities are illustrated in a database
Nested Queries Let us see some more complex queries in this section. Sub-queries: Some of the basic concerns of sub-queries are: A sub-query is a SELECT statemen
Describe the two alternatives for specifying structural constraints on relationship kinds? Relationship kinds have certain constraints in which limit the possible combination o
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