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Chapter 1 Database Management System (Part -I)

Database Management System

Grade 12


Data is the raw fact about anything which is unprocessed, un-interpreted or unorganized, but able to organize into useful information. For Example: Hari, Manager, Pokhara, 5 etc.


When raw data is processed and changed it into meaning data, then the meaningful data is called information. Information is processed, interpreted or organized data.

For Example: Ram, Student of MMC, Manager of Mega Bank, etc.


A database is a large collection of interrelated data of certain place, person or things in such a way that it can be easily access by an application program like DBMS. For Example: candidates of SLC exam, users of Facebook, users of NTC/NCELL etc.

Data Processing

The process of getting useful information from data by processing data with the help of database software is called data processing

Data storage hierarchy or components of a file

u BIT: smallest unit of memory. It can either 0 or 1

u Character: collection of 8 bits. It represents alphabet, number and anyone sign or symbol.

u Field: (data item/data element) holds single facts or attribute to an entity. It is as an attribute

u Record: a collection of related fields which represents a complete unit of information

u File: collection of related records.

u Table

u objects

Problems with file processing

u In a file processing system, data needed for each user application was stored in independent data files. File processing consisted of using separate computer program s that independent data files. Some problems are

u Data duplication:

u Data Dependence

u Lack of data integration

u Record: group of values of the attributes in predetermined order of an instance of an entity set. For eg: Anil Poudel 12 XII is a record of an entity set students.

u File is a collection or identical records in an entity set and is labeled to identify the entity set

u Field: A database field is a place for a piece of information in a record or file

u A database object in a relational database is a data structure used to either store or reference data. The most common object that people interact with is the table. Other objects are indexes, stored procedures, sequences, views and many more.


u Database is simply organised collection of related data arranged in a specific order so that it can be easily access, managed or updated

u Some of the examples are;

u Telephone directory

u Mark ledger

u Result sheet

u Flight schedule

Advantage of database

u It allows sharing large volume of data

u It allows searching of data quickly

u It reduces data duplication

u It allows advance filtering of data

DBMS (Database Management System)

u DBMS is a software which is used to store the data, process them and provide the useful information to the user.

u It involves in creating, modifying, deleting and adding data in database.

Advantage of DBMS.

u Reduce data redundancy

u Control data consistency: (any change made in one file automatically done in all field)

u Facilitates sharing of data

u Ensure data security

u Maintain data integrity: (make sure that database accept only the valid data)

Disadvantage of DBMS

u Required H/W and S/W are expensive.

u Costly and time-consuming procedures

u High operating cost

u Qualified persons are required to operate

u Difficult to recover backup

Database Models

Hierarchical Database model

u hierarchical database model is a data model in which the data are organized into a tree-like structure

u Data are stored as records which are connected to one another through links.

u  Each node is related to others in parent-child relationship.

u  conventional database model.

Network Model

u modified model of hierarchical model

u  each node may have several parents

u  higher level of flexibility than hierarchical

u  Easier to restructure

u  becomes complicated according to the increment in network

u  less user friendly than  hierarchical


Relational Database Model

u Data are arranged in two dimensional table which are easy for user to develop and understand.

u the basic data structure of relational data base is the table. data is presented as relationship or table of two dimension formed by rows and columns

u rows are also called records or tuples.

u the relationship identifies a set of entities(tuples) of the same type.


 u Relational Model (RM) represents the database as a collection of relations.

u A relation is nothing but a table of values.

u Every row in the table represents a collection of related data values.

u These rows in the table denote a real-world entity or relationship.

Object oriented database model

u An object-oriented database is a database that subscribes to a model with information represented by objects.

u Object is any real things that are available in the world which has own data and method so, is independent.

u Therefore objects contain both executable code and data.

u  There are other characteristics of objects such as whether methods or data can be accessed from outside the object.

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Khem Raj Poudel
Khem Raj Poudel
Khem Raj Poudel