Introduction to Database Management System

INTRODUCTION TO DATABASE & DATABASE MANAGEMENT SYSTEM
Data
Data is the plural form of the latin word “Datum” Which means raw facts and figures. So Data is the collection of facts and figures, which describe entities. An entity is thing having real existence.
Data Types

• Alphabetic data.
• Numeric data.
• AlphaNumeric data
• Sound
• Images
• Video
• Pointing

Data Management or Processing of Data: -
Making the data resource of an organization available for use and controlling its use is called data management or data processing. Its main purposes are listed below.

• Data collection.
• Data organization.
• Data storage.
• Data retrieval
• Data manipulation
• Data Analysis

There are two approaches towards data processing.

• Traditional/Conventional file approach.
• Data base approach.

Traditional/Conventional File approach
In this approach separate application program are written for individual data processing activities.
Traditionally a large organization would have different files for different purposes. For example there might be one file for course grades, another for students records and a third for tuition billing. Each file would be used independently to produce its own separate reports. If we change our address some one had to make the change separately in each file.







Course grade file                  Student Record file                 tuition billing File
Disadvantages of Traditional file Approach

• Data Redundancy

In file processing system, the same data (fields) may be duplicated in several files often in different formats. This is knows as data redundancy. When data fields are repeated in different files they waste storage space. Example: Suppose that there are two files of a student 1st is “Student Information” and 2nd is “Student Fee Detail” files, both files may contain system fields of data like, roll no, name, father name, address, phone # etc

• Lack of data integrity

Integrate means reliability and accuracy of data. The stored data must satisfy certain types of consistency constrains. Example: In above example file, Roll No, and Marks of students should be numeric value. It is very difficult to apply these constrains on files in file processing system.

• Program data dependency

Program data dependency is a relationship between data in files and program required updating and maintaining the files. Applications programs are developed according to a particular file format in file processing system. If the format of file is changed, the application program also needs to be changed accordingly. Example: If there is a change in the length of postal code, it requires change in the program. The change may be costly to important.
Database Approach
A database approach system is computerized record keeping system. It is a system whose overall purpose is to maintain data and make it available when it needed.
Data: is raw f acts in an organization
Base: is the main foundation and support for an organization on which an organization depends.
Database: Database is such data on which whole organization depends and need support of it.
Database is an organized collection of related data that is stored in an efficient and compact manner.
The word Organized means that data is stored in such a way that the user can use this data easily.
The word related means that a database is normally created to store the data about a particular topic.
The word efficient means that the user can search the required data quickly.
The word Compact means that the stored data occupies as little space as possible in computer.
Advantages of databases approach system
The advantages of databases approach system are as follows;

• Reduce data redundancy

Data redundancy can be controlled to some extent in database system, but it cannot be eliminated.

• Improved data Integrity: after controlling of data redundancy Lack of integration problem is controlled also
• More Program independence: Data is not dependent on programs
• Increased security: Database approach system provides better security features.

Disadvantages of databases and DBMSs
Although there are clear advantages to having databases and DBMSs there are still some disadvantages.

• Cost issue
• Back up and recovery issue
• Data vulnerability issue

The data storage hierarchy in a database
The data storage hierarchy consists of levels of data stored in a computer file. Bits, bytes (character), fields, records, files and databases as represented in Computers.

• Database: - A database is a collection of interrelated files. A vocational training institute database might include files on all past and current students in all departments. There would be various files for each student OJT_ record, session performance, personal record and so on.
• File: - A file is a collection of related records. And example of a file is collected data on every student in the same department of a VTI including all names, addresses, and ID#s
• Record: -A record is a collection of related felids. An example of a record would be our name, date of birth and ID

Hierarchy of Database

• Field: - A field is a unit of data consisting of one or more characters. An individual field typically contains a fact about a person, place thing or event. An example of a field is our name date of birth or ID number.
• Character: - Where as a byte is a unit of measure, a character is a singleton set of data such as a single letter, number or special character such as ; or $ or %.

Components of a Database System
The major components of a data base system are as follows.
DBMS (The Software)
A DBMS is a collection of programs that are used to create and maintain a database. DBMS is a general-purpose software system that provides the following facilities:

1. It provides the facility to define the structure of database. The user can specify data type, format and constraints for the data to be stored in database.
2. It provides the facility to store data on some storage medium controlled by DBMS.
3. It provides the facilities to insert, delete, update, and retrieve specific data to generate reports etc

Database: -
Database is an organized collection of related data that is stored in an efficient and compact manner.