Introduction of database system :
database system concepts

What is Database management system, or simply DBMS..?
Just, consider the phonebook of your mobile phone. It contains a list of all contacts. In general, this list includes contact names and numbers. But, it can also include some other data about contacts, such as address, birth-date, e-mail id, etc depending upon the features of your mobile. You can insert (store) new contact details in this phonebook, update (modify) existing contact details, delete (remove) some contacts if not required, or search for a particular contact. This phonebook has a database, collection of data about various contacts, and a set of programs, to perform various operations like as insert, update, delete and search. In short, the phonebook of your mobile phone is one kind of DBMS.

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This post provides an overview of database management system, formerly known as DBMS. Chapter begins with the description about basic concepts of database management systems such as data, information, database, and database systems. After this, various ways to store and manage data are described including paper based systems, file processing systems and database management systems with their advantages and disadvantages. This follows the overview of various terminology used in DBMS. This includes data administrator, database administrator, metadata, system catalog, data dictionary and data warehouse.

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DBMS – an overview

This section start with the description about data and information. It differentiates data and information – almost synonymously used terms in practice, but technically totally different from one another. After this, database and database systems are defined along with primary goals of DBMS. It follows description of operations that can be performed on DBMS and some of the well-known database-system applications.

What is database?

“A database is a collection inter-related data.”

It represents some aspect of the real world.
For example, consider a collection of customer id, name, address, contact number for some customer of a bank. Here, all the data – id, name, address, contact number – are inter-related. They all belong to some particular customer. In other words, they represent some particular customer.
Also, data about accounts, loans, employees, branches are inter-related in context of some banking system. So, these data, in combine, forms a database for a bank.

A database is some kind of collection of data. Though, any arbitrary (or random) collection of data is not considered as a database. For example, collection of some vehicle number, balance of account and percentage of student do not form a database.

Database management system

“A management system may be a collection of inter-related data and a group of programs to control those data.”

Data manipulation involves various operations like store data, modify data, remove data and retrieve data.
database system concepts

In other words, DBMS can be described as-
DBMS = Database + A set of Programs

Where database is referred as DB and a set of programs are referred as MS (Management System).
Database management system is also referred as database system only.

Notice here that, the database and software (a set of programs) together is called database system.
The primary goal of a DBMS is to provide efficiency and convenience in storing and retrieving database information.
DBMS also provides safety of the information against system crashes as well as an unauthorized access.

Operations performed on Database Systems

A database system can be considered as a container to store database. It also provides functionalities to manipulate database.
Various operations can be performed on such kind of database systems. Some of the basic operations are :
Creating containers for database such as tables, or files.
Inserting new data into existing database.
Modifying (or updating) data in existing database.
Removing (or updating) data from existing database.
Retrieving data from existing database.
Destroying containers for database such as tables, or files.
Along with these, a number of different operations can be performed on database systems depending upon the requirements of the system. These operations may include database back-up and recovery, performance monitoring, authorizing data access to provide safety to the database, and so on.

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Database system Applications

Now a day, DBMS are used in number of applications. Some of the well-known applications are listed in table given in

System                                            Data/Information to be managed
Banking system                              Customers, Accounts, Loans, Employees, Transactions…
Inventory system                            Items, Bills, Orders, Customers, Vendors, Employees….
Library system                                Books, Magazines, Authors, Publications, Students, staff, Faculties…
Railway reservation system           Train, Routes, Fairs, Schedules, Stations, Passengers, Reservations, Employees….
College/university                         Students, Subjects, Staff, Results, Scholarships…
Hospital management system       Patients, Doctors, Medicines, Employees, Wards, Instrument, Beds…
Cyber-CafĂ© management             Customers, Computers, Plans, Employees, Bills, Usages….

Data v/s Information

Data is plural form of ‘datum’. Data and information are generally represented in form of collection of
characters- digits and alphabets. But, in the world of computers, they can be in form of images, sounds,
or even videos.

Data means known facts, which will be recorded and have implicit meaning.
Information means processed or organized data.
Student no: 7047
Student name: “raj”
City name: ”vadnagar”
Account number: “A01”
Balance: 10000
Percentage : 84.66%
Run-rate in cricket match: 6.0 runs/over

Data convey something less, comparatively.
It is not convenient to represent result as marks of 5 subjects in form of -95, 56, 75, 90, 86.
Information conveys something more, comparatively.
It is convenient to represent result as a percentage in form of 84.66%
Data are row materials used to derive information
For example, masks of subjects.
Information is a product derived from data
For example, percentage.

Though, data and information are technically different form one-another, they are used synonymously in general practice and so, in this book also, they are used inter changeably.

Data storage: Paper-based v/s Computer-based system

Databases were right there before the invention of computers, and computer based database systems. At that time, databases were stored on papers. Still now, size of database is small, paper-based systems are used to manage it.
Paper-based systems are very simple to use. They don’t require any computer related skills. Also, they don’t require any investment in preparing programs, databases, and installing computers. So, they are cheap too.

But, they are convenient only when database size is smaller and data stored in database don not change. They become cumbersome with increase in database size. Some of the disadvantages of these paper-based systems, in comparison with computer-based systems, are as follows.
1.       Back-up

It is not possible to take faster and automatic back-up of database stored in hundreds or thousands of pages. Computer-based systems make this possible.
2.       Compactness

It is not possible to store data compactly. For example, to store all words of English Dictionary, hundreds of pages are required. While in computer based system, only few kilobytes of memory is required for this purpose.
3.       Data Retrieval

Data retrieval in paper-based systems requires too much manual effort. But, computer-based systems provide enhanced data retrieval in easy and efficient way.
4.       Editing

It is almost impossible to edit data written on papers. Such kind of editing will result in chaos. Computer-based systems do not suffer from such kind of problems. It is easy to edit any information stored in computers, in form of file or tables.
5.       Remote Access

It is not possible to access data stored on papers remotely. So, it becomes must for a user to access data at a location where these data are kept on papers. In computer-based systems, it's possible to access data remotely.

6.       Sharing
Sharing of data among multiple users at a same time is not possible in paper-based systems. Computer-based systems allow such kind of sharing.

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