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
An example of a weak entity is Staff because the availabilityID cannot be uniquely identified unless it is used in conjunction with the foreign key known as availabilityID in the A
Run the following queries. For each query show 1) What you expect the output to be based upon the data 2) the SQL code and 3) the output running the query in Oracle. 1. Show all c
what is natural join?
Domain Constraint It shows that each attribute in a relation has to contain an atomic value only from the corresponding domains. The data types associated with commercial RDBMS
Write A short note on temporary tables? Temporary Tables - Temporary tables exists solely for a particular session, or whose data persists for the duration of the transaction
Define upgrade and downgrade? It gives a mechanism for conversion from shared lock to exclusive lock is called as upgrade. It gives a mechanism for conversion from exclusive
Construct an ER diagram for a hospital along with a set of patients and a set of medical doctors Associate with every patient a log of the several tests and examinations conducted.
NEED FOR A DATABASE MANAGEMENT SYSTEM A Database is a structured, persistent collection of data of an organisation. The database management system (DBMS) manages the database o
Un-Normalized Form (UNF) If a table having non-atomic values at every row, it is said to be in UNF. An atomic value is something that cannot be further decomposed. A non-atomic
Define instance and schema? Instance: Collection of data kept in the data base at a particular moment is known as an Instance of the database. Schema: The 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