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!
Relations create the database. They must satisfy various properties, like no duplicate tuples, no ordering of tuples, and atomic attributes, etc. Relations that satisfy these basic needs may still have some undesirable characteristics such as data redundancy, and anomalies.
What are these undesirable characteristics and how can we eliminate them from the database system? This part is an attempt to answer this question. Though, please note that most of these undesirable properties do not arise if the database modelling has been carried out very carefully using some method like the Entity-Relationship Model. It is still important to use the methods in this unit to check the database that has been acquired and ensure that no mistakes have been made in modeling.
The central thought in these discussions is the concept of Database integrity, the notion of functional dependency, which rely on understanding the semantics of the data and which deals with what information in a relation is dependent on what other information in the relation. Our prime objective in this section is to describe the concept of data integrity, functional dependence and then describes normal forms using functional dependencies and using other types of data dependencies.
OBJECTIVES
After reading this section you should be able to
To eliminate duplicate rows (distinct operator) Example: SELECT DISTINCT DEPTNO FROM EMP;
Differentiate between static hashing and dynamic hashing. Ans: Static Hashing comprises the number of primary pages in the directory fixed. So, while a bucket is full, we requ
What should be declared explicitly in the corresponding ABAP/4 Statements to access internal tables without header lines & why? Work Area. This is needed as the Work Area is
What are aggregate functions? And list the aggregate functions supported by SQL? Aggregate functions are functions that take a collection of values as input and return a one va
management information system based on functional organisation
Now that she understands more about the benefits of databases, the play-scheme manager would like to extend the play-scheme database to include data for schools and instructors as
Define weak and strong entity sets? Weak entity set: entity set that do not have key attribute of their own are known as weak entity sets. Strong entity set: Entity set that
Define decision tree classifiers? As the name suggests decision tree classifiers use a tree: Every leaf node has an associated class, and every internal node has a predicate as
PHYSICAL DBMS ARCHITECTURE The physical architecture defines the software components used to process and enter data, and how these software components are related and interc
When are two schedules said to be view equivalent? Ans: Two schedules that is denoted as S and S' are said to be view equivalent if the subsequent three conditions are met
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