Chapter-2

Database Management Systems

Unit 2 Database 2.1 Concept of Database 2.1.1 Introduction: Data, Information, Database and DBMS 2.1.2 Objectives of DBMS 2.1.3 Database Model: Relational Model ,Network Model, Hierarchical Model, Entity Relational Data Model 2.1.4 Concept of Normalization 2.1.5 Types of Normalization 1NF, 2NF 2.1.6 Structured Query Language 2.1.7 Centralized Vs. Distributed Database 2.1.8 Data Security. 2.2 Design Database using DBMS Software 2.2.1             Create a Database 2.2.2 Create Tables and Fields and its properties 2.2.3 Create a Relational Databases 2.2.4 Create and Run Queries 2.2.5 Working with Forms 2.2.6 Generate Reports 2.3 Project Work on DBMS Software

Definition of Data

Data is the collection of raw (unprocessed) facts and figures without any added interpretation or analysis about persons, places and things which can be recorded in the form of words or texts, images, graphics, numbers, audios, videos, sounds etc.

Data have been collected, stored, processed and/or manipulated but have not been organized or placed into context.

For example:-Name, Roll, Marks obtained by student etc.

Examples of Data

1. Student Data on Admission Forms
   When students get admission in a college. They fill admission form. This form     contains raw facts (data of student) like name, father’s name, address of student etc. 
2. Data of Citizens
   During census, data of all citizens is collected.
3. Survey Data
   Different companies collect data by survey to know the opinion of people about their product.
4. Students Examination data
   in examination data about obtained marks of different subjects for all students is collected.    

Types of Data

There are following main types of Data.

1)  NUMERIC DATA
Numeric data consists of 0 to 9 digits, + and – sign and decimal point etc.
For example: 5, 44, 34.55, -45 etc

2)  ALPHABETIC DATA

It consists of all alphabetic letters A to Z, a to z and blank space etc.

For example: Nepal, KIC, SEMI etc.

3)  ALPHANUMERIC DATA

It consists of alphabet letters, digits and special characters like #, $, % etc.
For example: House Number 10-A, 14-August-1947, F-16 etc.

4)  GRAPHIC DATA   

Graphic data or image data consists of charts, graphs and images etc.

For example: a collection of maps of countries, a collection of family pictures etc.

5)  AUDIO DATA

Audio data consists of sounds and voices.

For example: audio songs, radio program, radio news, audio songs etc.

6)   VIDEO DATA

Video data consists of moving pictures.

For example: movie, TV dram, TV news etc.

7)  MIXED DATA

Mixed data consists of combined data of two or more types.

 For example:  TV drama consists of audio as well as video data. 

  

Definition of Information

Information is processed data after data processing which gives a complete sense or proper meaning. Information is useful in decision-making. 

Information of three students:

Id	names	address	roll
1.	Ram	Dharan	5
2.	Rajesh	Biratnagar	6
3.	Riya	Kathmandu	10

Field: - A field is the property or attributes of a table. Simply, a field is a piece of information about a person or place or thing. In above table Id, Name, Address, Roll is known as fields.

Record: - A collection of interrelated fields is called a record.  It is also known as tuple. A tuple is one record (one row). For example above table contains 3 records and each record has 4 related fields namely id, name address, roll.

Tables: -A database table is composed of records and fields that hold data. It organizes the data in the rows and columns form. 
                                                 Where, a row defines a record and a column defines a field.

File:- File is the collection of all related records.

Examples of Information

1. Student Address Labels
   stored data of students can be used to print address labels of students. 
2. Census Report (Total population, Literacy Rate, Male / Female ratio etc.)
   Census data is used to get report/information about total population of a country and literacy rate etc.
3. Survey Reports and Results
   Survey data is summarized into reports/information to present to management of the company.
4.  Result Cards of Individual Students, Result sheets of  a particular Class
   In examination system collected data (obtained marks in each subject) is processed to get total obtained marks of a student. Total obtained marks are Information. It is also used to prepare result card of a student.
5. Merit List
   after collecting admission forms from candidates, merit is calculated on the basis of obtained marks of each candidate. Normally, percentage of marks obtained is calculated for each candidate. Now all the candidates’ names are arranged in descending order by percentage. This makes a merit list. Merit list is used to decide whether a candidate will get admission in the college or not.

Compare between Data and Information

DATA	INFORMATION
Data is collection of raw facts and figures.	Information is processed data.
Data is unarranged and unorganized.	Information is arranged and organized.
Data is meaningless.	Information is meaningful.
Data is input.	Information is output.
Data is used less frequently.	Information is used frequently.
Data represents facts before processing.	Information represents results (obtained after processing).
Data is not helpful in decision-making.	Information is helpful in decision-making.
Data is raw material for information.	Information is the final product of data.
Data are unprocessed records	Information contains processed records
Data is in large amounts	Information is in small amounts
If data is lost, it is very difficult (or even impossible in some situations) to re collect.	If information is lost, it is easily derived from stored data, again.
Data is the asset of an organization and is not available for sale to public.	Normally, information is available for sale to general public.
Data depends upon the sources for collecting data, the collection methods adopted and the people who will collect data.	Information depends upon data.

Definition of Database

A database is an organized collection of interrelated information that can be used for multiple purposes as desired. Database is actually a place where related piece of information is stored and various operations can be performed on it.

An example of a database is a dictionary, where words are arranged alphabetically, and a telephone directory where subscriber names are listed in an alphabetic order, result sheet, salary sheet, attendance etc.

Objectives of database

v  Organized data storage.

v  Convenient retrieve of selected data.

v  Presented selected data in a convenient format.

v  Safety and security of data.

v  Integrity sharing and availability of data.