UNIT – VIII DATABASE MANAGEMENT SYSTEM, Lecture notes of Database Management Systems (DBMS)

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UNIT – VIII

DATABASE MANAGEMENT SYSTEM

Page no - 211

Database Concepts

Page no - 211

SESSION 1

 Data Comprises of numbers, alphabets or any other form like pictures,

sound etc. It is collected from various sources but not organized. Such data cannot be used directly to make meaningful decisions. Example of data are

 Sugam scored 704 marks out of 800.

 Ojas was born om 14th^ Feb, 2019.

 When data has been worked upon to give it more meaning, it is called

information. Some examples of information are:

 Danish scored more marks than Sugam did.

 Ojas is 17 years old now.

 Information is the data that has been organized and processed.

 To be useful to decision makers, information must be delivered to

the right person, at the right time, in the right place. It must be

accurate, timely, complete, concise and relevant.

 Data item or field: A set of characters which are used together to

represent a specific data elements, They are also known as field.

E.g. Roll number of a student may be represented as Roll_No.

 Record: Collection of fields is called Records. E.g. The class

record for a student contains such data fields as Roll_No., Name,

Marks etc.

 File: Collection of records is called a file. E.g. A class file might

consist of the student marks record for a class.

Database is the collection of interrelated data e.g. Consider the

names, telephone numbers and addresses of people you know. This is a collection of related data and hence database.

It is managed by an individual(or group) called the Database

Administrator(DBA), who is responsible for designing, creating and maintaining the database to satisfy the needs of users.

All access to database is controlled by a sophisticated software

package called Database management System (DBMS).

DBMS is the collection of interrelated data and a set of

procedures to access that data.

 RDBMS stands for Relational Database

Management System.

 A relational database system contains of

a collection of tables , each of which is

assigned a unique name i.e. A relational

model represents the database as a

collection of relations.

 A relation is a table with columns and

rows.

Name Age City Suresh 25 Banglore Amit 29 Banglore Sudhir 24 New Delhi

• It has three column headers : Name,

Age and City.(Called Attributes )

• The row of a table is called as tuple,

so there are 3 tuples.

• The degree of a relation is the

number of attributes it contains, there are 3 attributes or degree three.

• The most popular DBMS includes:
• Open office base
• Microsoft Access
• Microsoft SQL Server
• MySQL
• Oracle

 PRIMARY KEY: Primary key is asset of one or more attributes that can

uniquely identify tuples within the relation.

 CANDIDATE KEY: All attributes combinations inside a relation that can serve

as primary key are candidate keys as they are candidate for primary key position.

 ALTERNATE KEY: A candidate key which is not the primary key is called an

alternate key.

 SUPER KEY: A super key is a set of one or more attributes that, taken

collectively, allows us to identify uniquely an entity in the entity set.

 FOREIGN KEY: A non-key attribute, whose values are derived from

the primary key of some other table, is known as foreign key in the

current table.

Database management

system is a collection of interrelated data and a set of programs to access that data..

The main goal of DBMS is to

provide a way to store and retrieve database information that is both convenient and efficient.

Data: collection of related information.

Hardware: consists of secondary storage like DVD ROM, USB devices, The processor and associated main memory.

Software: required software for query.

Users: includes all types of users

Procedures: General instructions to use DBMS, includes procedure to setup and install a DBMS, to login n logout, to manage etc.