Definitions :
Data :
Data is considered as accurate and reliable facts. A fact may be text, number, sound, picture etc.
Eg:
A salesman maintains their customer’s address, phone number of all their customers. These facts are called as data.
Information :
When the data is organi...
Data is considered as accurate and reliable facts. A fact may be text, number,
sound, picture etc.
Eg:
A salesman maintains their customer’s address, phone number of all their
customers. These facts are called as data.
Information :
When the data is organized into a meaningful format, at that point it
becomes information.
Database :
It is a system which is designed to meet the information requirement of
people at different levels with in the organization.
(Or)
It is a place where we keep the data permanently on the secondary storage
device during the application process.
Note :
Any information system has 2 important components.
1) Software
2) Data
,DBMS (Data base Management System) :
It is a software which allows the user to access the information from the data
base.
The objective of DBMS is to provide a convenient and efficient methods
for adding, modifying, removing and distributing the data.
Entity :
It is a basic building unit to construct the database and it represents real
world objects.
Eg :
A student in a college.
Entity set :
A group of similar interrelated set of objects are considered as entity set.
Entity set is also called as relation(RDBMS), or table(oracle).
Attribute :
It is a property of the entity set. At the time of adding attributes to the entity
set, we should take care whether it is useful or not to the organization.
Attribute is also called as column or field or port.
Attribute value :
It is a value allowed to stored into appropriate attribute.
Domain :
A set or list or values which are permitted to store into the attribute.
Eg :
Marks of student is permitted between 0 and 100 are known as domain,
negative marks and marks greater than 100 are not allowed.
,Types of attributes :
1. Simple attributes
2. Composite attributes
3. Single value attributes
4. Multi value attributes
5. Derived attributes
Simple attributes :
If the attribute is not possible to divide into sub parts is called as simple
attributes.
Eg :
Rollno, Pincode, etc
Composite attributes :
If one attribute is possible to divide into sub parts is called as composite
attributes.
Eg :
Name, Address etc.
Single value attributes :
If the attribute is used to identifying one particular instance in database is
called as single value attribute.
Eg:
Emp no, Account number, Roll no etc.
Instance
Emp No : 101
Emp Name : RAJI
Job : Software Engineer
Salary : 1,00,000
, Multi value attributes :
If the attributes allows more than one type of value
Eg:
Course, Telephone number which allows multiple values as land number,
mobile number etc.
Derived attributes :
If one attribute value depends on another attribute is called as derived
attributes. Here existing attribute in database is called as stored attribute and
new one is called as derived attribute.
Eg :
1. Age(derived attribute) depends on data of birth(stored attribute)
2. Experience(derived attribute) depends on data of joining(stored attribute)
Data base :
A data base is an electronic collection of information designed to meet
a handful of needs.
Data base must provide mechanism to retrieve data quickly as
applications interact with their contents.
RDBMS : Relational Data Base Management System
To be able to function, an organization needs information, example
list of books in a library, customer details in retail business.
A major requirement of any computer system is to store and retrieve
data in a way that is meaningful to the end user. So the core of any
information system is data, which is to be transformed into information
through data modeling.
The DBMS is the software and collection of tools that manages the
data base.
A RDBMS is a data base management system that based on the
relational model. The objective of RDBMS is to achieve normalization of
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