CHAP-3 PART-B
Database Management System
Data is most important for any organization or in a company, the
organization’s primary objective is to store data, manage data and retrieve
data from computers and this is only possible with database management
systems.
A database is an organized collection of data that is maintained electronically.
Any kind of data like text, numbers, pictures, videos and files can be stored in
a database. This data can be stored, retrieved and edited using software
known as a database management system
DATA AND INFORMATION
Data – Data is a collection of facts which do not have any meaning.
This data is unstructured information such as numbers, text, symbols
and images.
Information – Information depends on data, this information has some
meaning. This Information refers to organized and structured data.
Databases and DBMS
Database – A database is a collection of logically related data items
stored in an organized manner, It is also considered as a data bank.
DBMS (Database Management System) – This software that is used
to create, update and retrieve data is known as database management
system. Some of the common examples of DBMS are LibreOffice Base,
MS Access, Open Office Base, Oracle, MySQL.
Advantages of DBMS
Organized Storage – In database data are stored in an organized
manner, so that retrieval of the data is fast and accurate.
Data Analysis – In database you can retrive the data based on certain
criteria for example average, maximum or minimum value etc.
Data Sharing – Databases can share the data with other applications.
Minimal Data Redundancy – In database duplicate data is not allowed,
it means that same data will not be repeated in the table.
Data Consistency – In database if any record is changed in any one of
the tables then the same data will update in other tables also.
Increase Efficiency – In the database the data is organized which
helps to retrieve and search data efficiently.
Increases Accuracy – In the database the data is retrieved accurately
from the database.
Increases Validity – In the database the valid data is being entered
and checked by the database.
Security – Unauthorized access is not allowed in the database
DATA MODELS
This structure of the database is known as a data model. The data models
describe the relationships between the data. A database can be designed in
different ways dependent on data storage.
There are different data models such as –
Hierarchical data model
Network data model
Relational data model
Hierarchical Data Model
In Hierarchical Data Model the data is organized like tree structure and data is
stored in the form of a tablNetwork Data Model
In this model, multiple records are linked to the same master file. This network
model is considered as a tree where the master table present in the bottom
and other tables linked to the master table.
Relational Data Model
In relational data models are based on relationships between two or more
tables of the same database. This is the most popular data model.
Relational Database Model
E. F. Codd given the concept of Relational Database Model in 1970. The most
popular type of database model is the relational model. In relational database
models the data elements are stored in different tables, this table is related
through the common fields.
Relational Database Terminology
Some of the common terms used in RDBMS.
Entity – Entity is a piece of data that is stored in the database, for
example student rollno, name and age is the entity of the student
record.
Table – Table is a collection of logically related records, It is organized
as a set of columns.
Field or Columns or attributes – The smallest entity in the database is
known as field, a collection of fields is known as record, a collection of
records make a table and a collection of tables make a database.
Data Values – Data values are raw data represented in character,
numeric or alphanumeric.
Record or Row – The collection of data values of all the fields are
known as record.
Primary Key – The field which uniquely identifies a row in a table. The
primary key used to be a unique identifier for the table.
Relational Database – A relational database is a collection of related
tables.
Foreign Key – The field or a combination of fields of one table can be
used to uniquely identify records of another table, then that particular
field is known as the foreign key.
Candidate Key – All the field values that are eligible to be the primary
key are the candidate key for that table.
Alternate Key – One or two fields in the table are made as primary key
but others are the alternate key.
Objects of an RDBMS
The database is a collection of object or a feature that is used to store,
represent or retrieve data, different types of objects in a database are given
below –
Table – Table is a collection of row and column which is used to store
data. The data in the database is first stored in a table.
Form – A form is used to enter data in a table, form is the interface
between database and users, it is an easiest method to enter data in
database using user friendly manners. A form consists of a text box,
radio button, labels, check box etc.
Queries – Queries are used to retrieve the desired result from the
database.
Reports – The output of any query in the database may be displayed in
the form of reports.
Components of a Table in DBMS
1. Table Name
o Every table must have a unique name.
o Example: Student, Employee, Library.
2. Fields / Columns / Attributes
o Vertical part of the table.
o Represent the type of data stored (like Name, Roll_No,
Age).
o Each field has a data type (e.g., Text, Integer, Date).
3. Records / Rows / Tuples
o Horizontal part of the table.
o Each row represents one complete set of related data.
o Example: A student’s details (Roll_No, Name, Class).
4. Cells
o The intersection of a row and a column.
o It contains the actual data value.
o Example: In row 1, column "Name" → Rahul.
5. Primary Key
o A field (or combination of fields) that uniquely identifies
each record in the table.
o Example: Roll_No in the Student table.
6. Foreign Key (when linked to another table)
o A field in one table that refers to the primary key of
another table.
o Helps in maintaining relationships between tables.
📊 Example Table: Student
Roll_No (PK) Name Class Age
101 Rahul 10A 15
102 Sneha 10B 14
103 Arjun 10A 15
Table Name → Student
Fields / Columns → Roll_No, Name, Class, Age
Records / Rows → Each student’s details
Cells → Intersection of Roll_No=101 and Name=Rahul
Primary Key → Roll_No
