Database Approach
Database technology eliminates many of the problems of
traditional file organization by organizing data:
centralizing data and controlling redundant data and serve
many applications and different groups at the same time.
The database approach is an improvement
on the shared file solution as the use of a database management system (DBMS)
provides facilities for
(1) querying (monitoring),
(2) data security and integrity, and
(3) allows simultaneous access to data
by a number of different users.
Some important
terminology:
·
Database: A database is a collection of
related data.
·
Database
management system: The
term 'database management system', often abbreviated to DBMS, refers to a
software system used to create and manage databases. The software of such
systems is complex, consisting of a number of different components.
·
System
catalogue / Data dictionary: The
description of the data in the database management system.
·
Database
application: Database
application refers to a program, or related set of programs, which use the
database management system to perform the computer-related tasks of a
particular business function, such as order processing.
In order to
remove all limitations of the File Based Approach, a new approach was required
that must be more effective known as Database approach.
The Database is a shared collection of logically related
data, designed to meet the information needs of an organization. A database is
a computer based record keeping system whose over all
purpose is to record and maintains information. The database is a single, large repository of
data, which can be used simultaneously by many departments and users. Instead
of disconnected files with redundant data, all data items are integrated with a
minimum amount of duplication.
The database
is no longer owned by one department but is a shared corporate resource. The
database holds not only the organization’s operational data but also a
description of this data. For this reason, a database is also defined as a
self-describing collection of integrated records. The description of the data
is known as the Data Dictionary or Meta Data (the ‘data about data’). It is the
self-describing nature of a database that provides program-data independence.
A database
implies separation of physical storage from use of the data by an application
program to achieve program / data independence. Using a database system, the
user or programmer or application specialist need not know the details of how
the data are stored and such details are “transparent to the user”. Changes (or
updating) can be made to data without affecting other components of the system.
These changes include, for example, change of data format or file structure or
relocation from one device to another.
In the DBMS
approach, application program written in some programming language like Java, Visual Basic.Net, and Developer 2000 etc. uses
database connectivity to access the database stored in the disk with the help
of operating
system’s file
management system.
E.g., The file system interface and DBMS interface for
the university management system is shown.
Building blocks of a Database
The following three components form the building blocks of
a database. They store the data that we want to save in our database.
1. Columns. Columns are similar to fields,
that is, individual items of data that we wish to store. A Student’s Roll
Number, Name, Address etc. are all examples of columns. They are also similar
to the columns found in spreadsheets (the A, B, C etc. along the top).
2. Rows. Rows are similar to records as
they contain data of multiple columns (like the 1, 2, 3 etc. in a spreadsheet).
A row can be made up of as many or as few columns as you want. This makes
reading data much more efficient – we fetch what you want.
3. Tables. A table is a logical group of
columns. For example, we may have a table that stores details of customer’s
names and addresses. Another table would be used to store details of parts and
yet another would be used for supplier’s names and addresses.
It is the tables that make up the entire
database and it is important that we do not duplicate data at all.
Characteristics of
database
The data in a database should have the
following features:
Organized
/ Related. It should be well organized and
related.
Shared. Data
in a database are shared among different users and applications.
Permanent. Data
in a database exist permanently in the sense the data can live beyond the scope
of the process that created it.
Validity/integrity/Correctness. Data
should be correct with respect to the real-world entity that they represent.
Security. Data
should be protected from unauthorized access.
Consistency. Whenever
more than one data element in a database represents related real-world values,
the values should be consistent with respect to the relationship.
Non-redundancy: No
two data items in a database should represent the same real-world entity.
Independence. Data
at different levels should be independent of each other so that the changes in
one level should not affect the other levels.
Easily
Accessible. It should be available when and
where it is needed i.e., it should be easily accessible.
Recoverable. It
should be recoverable in case of damage.
Flexible
to change. It should be flexible to change.
To
create, manage and manipulate data in databases, a management system known as Database
Management System (DBMS) was developed.
No comments:
Post a Comment