CONCEPTS OF DATABASE MANAGEMENT SYSTEM

 Chapter 10 
Concepts of database management system

A database is an organized collection of Data.

Database Management System

A database management system is a software package with computer programs that

controls the creation, maintenance, and use of a database. It allows organizations to

conveniently develop databases for various applications. DBMSs include Oracle, IBM DB2, Microsoft SQL Server, Microsoft.

Data can be organized into two types:

• Flat File: Data is stored in a single table. Usually suitable for less amount of data.

• Relational: Data is stored in multiple tables and the tables are linked using a common

field. Relational is suitable for medium to large amount of data.

Advantages Of DBMS

 Reduces Data Redundancy

The database management systems contain multiple files that are to be stored in many

different locations in a system or even across multiple systems. Because of this, there

were sometimes multiple copies of the same file which lead to data redundancy.

This is prevented in a database as there is a single database and any change in it is reflected

immediately. Because of this, there is no chance of encountering duplicate data.

 Sharing of Data

In a database, the users of the database can share the data among themselves. There are

various levels of authorization to access the data, and consequently the data can only be

shared based with the authorized users.

Many remote users can also access the database simultaneously and share the data

between themselves.

 Data Integrity

Data integrity means that the data is accurate and consistent in the database. Data Integrity

is very important as there are multiple databases in a DBMS. All of these databases

contain data that is visible to multiple users. So it is necessary to ensure that the data is

correct and consistent in all the databases and for all the users.

 Data Security

Data Security is an important concept in a database. Only authorized users should be

allowed to access the database and their identity should be authenticated using a username

and password. Unauthorized users should not be allowed to access the database under any

circumstances as it violates the integrity constraints.

 Privacy

The privacy rule in a database states that only the authorized users can access a database

according to its privacy constraints. To secure data levels are set in the database and a

user can only view the data which is allowed to be seen. For example - In social

networking sites, access constraints are different for different accounts a user may want

to access.

RDBMS

A relational database is a type of database. It uses a structure that allows us to identify

and access data in relation to another piece of data in the database. Often, data in a

relational database is organized into tables.

Keys

Primary key: a primary key is a set of one or more fields that uniquely identifies each record in a table

Composite Primary Key : a composite key refers to a combination of two or more attributes that uniquely identify the records in a table. 

Foreign Key: A foreign key is a field or set of fields that is used to establish a relation b/q the two tables

It consists of one or more fields whose value matches with a primary key in another table