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!
Dependency Preservation
It is obvious that the decomposition must be lossless so that we do not lose any information from the relation that is decomposed. Dependency preservation is another main requirement since a dependency is a constraint on the database. If each attributes appearing on the left and the right side of a dependency appear in the similar relation, then a dependency is considered to be preserved. Therefore, dependency preservation can be checked simply. Dependency preservation is important, because as stated previously, dependency is a constraint on a relation. Therefore, if a constraint is split over more than one relation (dependency is not preserved), the constraint would be complex to meet. We will not talk about this in more detail in this unit. You may refer to the more readings for more details. Though, let us state one basic point:
"A decomposition into 3NF is lossless and dependency preserving whereas a decomposition into BCNF is lossless but may or may not be dependency preserving."
Why do you go for sorting your query results? SQL SELECT command to fetch data from MySQL table. Whenever you select rows, the MySQL server is free to return them in any order
An entity set that does not have sufficient attributes to form a primary key is called? An entity set that doesn't have sufficient attribute to form a primary key is known as w
Define rotational latency time. The time spent waiting for the sector to be accessed to appear under the head is known as the rotational latency time.
Benefits of Sequential File Organisation It is quick and efficient when dealing with huge volumes of data that require being processed periodically (batch system). Dra
The Concurrent Transactions Almost every commercial DBMS support multi-user environment. Therefore, allowing multiple transactions to proceed concurrently. The DBMS must make
Find a 3NF decomposition of the following relation scheme: University (Faculty, Dean, Department, Chair, Professor, Rank, Student}. The University relation satisfies the following
Explain the Recoverable Schedule A recoverable schedule is one in which for each pair of transactions Ti and Tj such that Tj reads a data item formerly written by Ti, the comm
Explain outer join? Outer Join - If there are any values in one table which do not have corresponding value(s) in the other, in an equi-join which will not be chosen. Such ro
What is a query tree? Ans: A query tree, as well known as operator graph, is a tree data structure that corresponds to a relational algebra expression. It denotes the inpu
Probelm: (a) A distributed database (DDB) is a collection of multiple, logically interrelated databases which are physically distributed over a computer network" (i) Give a
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