Database Management System
Grade 12
Data:
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.
Information:
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.
Database:
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.
Database
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 A 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 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.
