DATABASE MANAGEMENT
SYSTEM[DBMS]
2620003
[Unit: 1]
Prepared By
Lavlesh Pandit
SPCE MCA, Visnagar
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 INTRODUCTION OF DBMS
 Data:
 Data are Known facts and that can be recorded and that have implicit meaning.
 Data is rows facts or figures collected about entity.
 Anything can be data.
 Data is information that has been translated into a form that is more convenient
to move or process
For e.g., Student information
Student Enrollment no
Stud Name
Stud Address
Contact Number
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Entity
Entity is any real world object it may be place, person, thing concept or
theory about which we are storing the data.
Attributes
Attributes are property (characteristic) of an entity.
An attribute is a specification that defines a property of an object.
Database
The database organized collection of related information.
A database is a collection of persistent data that is used by the application
system of some given enterprise.
Collection of computerized data file is also known as database.
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Database system
The Database System is basically a computerized record keeping system
which is used to store the information and allows the user to retrieve and
update the information on demand.
It is a computerized system whose overall purpose is to store information
and to allow users to retrieve and update that information On user demand.
The Database has for major component.
 Data
Hardware
Software
Users
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 Data
It is a very important component of the database system. Most of the
organizations generate, store and process large amount of data.
The data stored in the system is partitioned into one or more
database.
The data is divided into different parts:
Integrated Data
Shared Data
Meta Data
Integrated data:
Data integration involves combining data residing in different sources
and providing users with a unified view of these data
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 Shared Data:
 Shared data means that individual pieces of data in the database can be
shared among different users , in the sense that each of those users can
have access to the same piece of data , possibly for different purposes.
 Metadata:
A description of the structure of the database is known as Metadata. It
basically means "data about data". System Tables store the Metadata, which
includes.
-Number of Tables and Table Names
-Number of fields and field Names
-Primary Key Fields
Application Metadata - It stores the structure and format of Queries,
reports and other applications components.
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Hardware:
Your PC (Personal Computer) is a system, consisting of many components.
Some of those components, like Windows XP, and all your other programs, are
software. The stuff you can actually see and touch, and would likely break if
you threw it out a fifth-story window, is hardware.
Ex…Printer to print the information and hard disk to store information.
Software:
Computer software, or just software, is a collection of computer programs
and related data that provides the instructions for telling a computer what
to do and how to do it.
Software is often divided into two categories. Systems software includes
the operating system and all the utilities that enable the computer to
function.
Applications software includes programs that do real work for users. For
example, word processors, spreadsheets, and database management
systems fall under the category of applications
software.
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User:
Users are those persons who need the information from the database to
carry out their primary business responsibilities i.e. Personnel, Staff,
Clerical, Managers, and Executives etc. On the basis of the job and
requirements made by them they are provided access to the database
totally or partially.
We people are considered as database application user.
Users of the DBMS
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Information
 Meaningful data is known as information.
Information is the summarization of data in a presentable form.
Fundamentals of Database
Users of the system can perform a variety of operations an such files-for
example:
•Adding new, empty files to the database;
•Inserting data into existing files;
•Retrieving data from existing files;
•Changing data in existing files;
•Deleting data from existing files;
•Removing existing files from the database.
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Database Management System(DBMS)
A Database Management System is a software system that is used
both to create Databases and manage the information stored within it.
The end users and application programmers are enable by DBMS
software to share data.
It providing systematic method to creating , updating , retrieving and
storing information in a database.
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Characteristics of DBMS
•Self describing nature of database system
•Insulation between programs and data abstraction
•Support of multiple views of data.
•Shared between different users
•Always Persistence
•Correctness of data
•Provide high Security
•Non-Redundant
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Self Describing Nature of database system
• A fundamental approach of the database is that the database system
contains not only the database it self but also a complete description of
database structure and constraints.
• The definition is store inside DBMS catalog which contain information such
as the storage of each file, the data type and storage format of each data
item and various constraints on the data.
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Insulation between programs and Data Abstraction
•In tradition file processing system the structure of a data file are embedded
in application program so any changes to the structure of a file may require
change in the complete program.
•By contras the DBMS access the program that does not require changes in
the most of the cases. The structure of the data file are stores inside the
DBMS catalogue separately from the access programs, we call this property
Program & Data Independence.
Support of Multiple Views of Data.
A database typically has many numbers of user, each of them requires
deferent different view of data. A view may be substitute of database or it
may be contain virtual data that are derived from database file.
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Shared between different Users
•Data in database are shared among different users and application.
•A multi-user DBMS as is name implied must allow the multipal user to
access the database as the same time.
Always Persistence
•Data in a database exist permanently in the sense that data can live
beyond the scope of the process that created it.
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Correctness of data
•Data should be correct with respect to the real world entity that they
represent.
Provide high Security
•Data should be protected from Un-Authorized access.
Non-Redundant
•No two data items in a database should represent the same real world
entity.
E.g. Same roll no. does not represent the same Student
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Elements of Database
The following are the various elements of database…
I.
II.
III.
IV.
I.
Data items
Entity and attribute
Logical and physical data
Schema
Data items:
•Data item means pies of information. It is stored as a file.
II. Entity and attribute
•
Entity is any real world object it may be place, person, thing concept or
theory about which we are storing the data.
•
Attributes are property (characteristic) of an entity.
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III. Logical and Physical data
•The term logical structure refers to the way the programmers look as the
database and physical structure referred to the way the data which are
actually store in a database on specific storage device.
IV. Schema
•The term scheme mains of overall chart of the data item and reword
store in a database.
•Description of database is called database schema.
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 Instance and Schema
•
The DB schema is corresponds to the variable declarations along
with associated type definitions in programs.
•
The formal definition of database schema is set of formulas that
specify integrity constraints that are applied on the database.
•
Schema contains 'No of records + Type of data + No of attributes’.
•
The schema defines the table fields , relationship , views , indexes ,
packages , procedures , functions , queues , triggers , types .
Sequences , materialized view , synonyms , DB links , java and XML
schemas and other element.
•
Not change frequently.
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 Schemas Example
account_n
umber
branch_name
balance
branch_name
branch_
city
assets
A-101
Kalawad Road
500
Kalawad Road
Rajkot
7100000
A-215
Maninagar
700
University Road
Rajkot
9000000
A-102
Vastrapur
400
Maninagar
Ahemdabad 400000
A-305
S.G.Road
350
Patel Nagar
Delhi
A-201
University Road
900
Vastrapur
Ahemdabad 1700000
A-222
M.G.Road
700
Hawda
Kolkatta
300000
A-217
University Road
750
Kandiwali
Mumbai
2100000
S.G.Road
Ahemdabad 8000000
3700000
Account_schema=(account_number , branch_name , balance)
Branch_schema = (branch_name , branch_city , assets)
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 Database Instance :

The DB instance is corresponds to the value of the variables in a programs
at a point in time corresponds to an instance of a database schema.

The collection of information stored in the DB at particular time is called
Instance of DB state or snapshot.

The DB instance update every time where data are added or update.

Schema is called intension and Instance is called Extension.
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 Types of Schemas :
The types of DB schemas are listed below
1)
Physical Schema : This describes the DB design at physical level.
2)
Logical Schema : This describes the DB design at the logical level.
3)
Subschema : DB have several schemas at view level. that describe
different view of the DB
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Database System Applications
1)
Banking : For Customer information , accounts ,loans , and banking
transaction
2)
Airlines : For reservation and schedule information. Airlines were among first
to use databases In a geographically distributed manner.
3)
Universities : For Students information , course Registration and grades.
4)
Credit Card Transaction : For purchases on credit cards and generation of
monthly statements.
5)
Telecommunication : For keeping records of calls made, generating monthly
bills, maintain balances on prepaid calling cards , and storing information about
the communication networks.
6)
Sales : For Customer , Products and purchase information.
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Advantage of DBMS
•The Data can be shared between User
•Controlling Redundancy
•Restricted unauthorized access
• Inconsistency can be avoided ( To Some Extent)
•Providing multiple User Interface
•Transaction support can be provided
•Standards can be enforce
•Represent complex relationship among data
•Provide Backup and Recovery
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•The Data can be shared between User
•A database allows the sharing of data under its control by any number of
application programmes or users.
•Many User can see data at a given time.
•Redundancy can be reduced
Centralized control of the data by the DBA avoid unnecessary duplication
data and effectively reduce that total amount of data.
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•Restricted unauthorized access
o DBA can ensure that the only means of access to the database is
through the proper channels, and hence can define security constraints
to be checked whenever access is attempted to sensitive data.
o Different constraints can be established for each type of access (
retrieve, insert, delete, etc ) to each piece of information in the database
•Inconsistency can be avoided
o If the given fact is represented by single entry ( i.e if the redundancy is
removed), then such an inconsistency cannot occur.
o Alternatively, if the redundancy is not removed but is controlled (by
making it known to the DBMS), then the DBMS can guarantee that the
database is never inconsistent as seen by the user.
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•Transaction support can be provided
-A transaction is a logical unit of work typically involving several database
operations- in particular, several update operations.
-The standard example involves the transfer of a cash amount from one account A to
another account B. Clearly two update are required here, one to withdraw the cash
from account A and the other to deposit it to account B.
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 View of Data
 Data Abstraction
•
To retrieve data effectively
•
Efficiency is needed into database to represent data in a complex
structure
•
Due to some non computerized data users , developer hides the
complexity from users through several levels of abstraction , to simplify
users interaction with database system.
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The Three Level Architecture of DBMS.
1. Physical Level (Internal level)
2. Logical Level(Conceptual level)
3. View Level (External Level or User Level)
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1. Physical Level (Internal level)

The internal level or physical level is physical representation of the
database on the computer

The lowest level of abstraction

Describe How data are actually stored

Describe Low level data structure in detail

How the data is stored physically and where it is stored in database.
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3. What data users and
application programs see ?
2. What data is stored ?
describe data properties
such as data semantics,
data relationships
1. How data is actually
stored ?
e.g. are we using disks ?
Which file system ?
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2. Logical Level(Conceptual level)
This is next higher level of abstraction
• What information or data is stored in the database (like what is the data type or what is
format of data.)
• And also describe what kind of relationship between those data
• Here whole Database is divided into small simple structures
• Users at this level need not be aware of the physical-level complexity used to
implement the simple structures
•Generally, database administrators (DBAs) work at logical level of abstraction.
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3. View Level (External Level or User Level)
•It is the highest level of abstraction.
•The external level is user’s view of the database.
•It describes only a part of the whole Database for particular group of users.
•This view hides all complexity.
• It exists only to simplify user interaction with system.
•The system may provide many views for the whole system.
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 Data Model
•Data Models are internal Structure of Database.
•It is collection of conceptual tools for describing data , data relationships ,
data semantics , and consistency constraints.
•A data model provides a way to describe the design of a database at the
physical , logical and view level.
•The data models can be classified in different categories…
 E-R Data Model
 Relational Data Model
 Object Oriented Data Models
 Semi structured Data Model
 Hierarchical database model
 Network Data Model
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E-R Data Model
•The E-R model is a high-level data model.
•E-R model is basically used to design logical database Structure.
•The logical structure of database can be expressed graphically by E-R
diagram.
•E-R model is widely used in database design.
•Some specific Symbols or Blocks are used to represent E-R diagram
Advantages of E-R Model
•Easy Conversion from E-R to other data models
•Graphically representation for better understanding.
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 To built the E-R model we use the following components
1.
Entities: Specify the item of application to storing the data.
2.
Relationship: Used to connect entities and define the relationship between
entities.
3. Attributes: Define the properties of Entities.
An E-R diagram is expressed graphically which consist following components
I.
Rectangle : Use to represent Entities
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II. Ellipses: Represent attributes.
III. Diamonds: Represent Relationship among Entities.
IV. Lines: Link entities to relationships and relationships to entities
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Figure: Sample E-R Diagram
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Types of Relationship in E-R data model
I. One-to-One(1:1)
II. One-to-many(1:M)
III.Many-to-One(M:1)
IV.Many-to-Many(M:N)
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 Relational Data Model
•The Relational model is collection of table to represent both data and the
relationships among those data.
•Each table has multiple column and each column has unique name.
•Each table contains records of a particular type.
•A Relation model represents the database as collection of relations.
•The Relational Data model is simplified the user’s view of the database.
•Tables are related with each other by sharing common entity characteristics
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• Suppose two tables are CUSTOMER and AGENT.
•
CUSTOMER table contains fields are
CUST_ID
CUST_NAME
CUST_PHONE
AGENT_ID.
•
AGENT table contains field are
AGENT_ID
AGENT_NAME
AGENT_PHONE
AGENT_SAL.
• Even data are stored into different table , the common link b/w the
CUSTOMER and AGENT table is AGENT_ID.
• Although both table are completely independent of one another , data b/w
the table can be easily connect using common links.
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CUSTOMER
AGENT
CUST_ID
AGENT_ID
CUST_NAME
AGENT_NAME
CUST_PHONE
AGENT_PHONE
AGENT_ID
AGENT_SAL
Advantages of Relational Data Model
•Simplicity
• Flexible and powerful query capability
•Ease of design , implementation , maintenance and uses
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Terms use in Relational data model
1. Relational database store data in the form of tables.
2. The rows of the table are called as tuples.
3. The columns of the table are known as attributes.
4. Every attributes has a datatype associated with it.
5. Tables are called as relations.
6. The table name are called as relational variables
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Object Oriented Data Models
•Relational DB is widely successful in variety of application areas.
•However it does not support the distribution of database across the number of
servers.
•Due to these reasons , ODBMS is developed.
•ODBMS is among the most recent approaches to the DBMS.
•They started in the engineering and domain application.
•It has capacity of storing different types of data for example , pictures ,voice ,
video , including text , numbers and so on.
• It is capable to combine object oriented programming with database
technology and thus providing an integrated application development system.
•It provides powerful features like inheritance , polymorphism.
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Semi structured Data Model
•The semistructured data model is permits the specification of data
where individual data of same type may have different set of
attributes.
•The XML(Extensible Markup Language) is widely used to represent
semistructured data.
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Database Language
•A database system provides a data-definition languages(DDL)
to specify the database schema and a data manipulation
Language(DML) to express database queries and updates.
•These two are not different languages , they are simply form
parts of a single database language , such as SQL
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Data-Definition Language
•A language by which we can specify database schema by a set of
definitions that is called data definition languages.
•The DDL is also used to specify additional properties of the data.
•We can specify storage structure and access methods used by the
database system by a set of statement in a special type of DDL called
data storage and definition language.
•This statement define the implementation details of the database
schemas, which are usually hidden form the users.
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•The
data value stored in the database must satisfy certain
consistency constraints.
i.e. the balance on an account should not fall below $100.
•The
DDL provides facilities to specify such constraints.
•The
database system check this constraints every time and database
is update.
•DDL Commands
are…
Create , alter , drop , truncate, rename.
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Data Manipulation Language
A data manipulation language is a language that enables users to
access or manipulate data as organized by the appropriate data
model.
The types of access are :
1) Retrieval of information stored in the database.
2) Insertion of new information into the database
3) Deletion of information from the database
4) Modification of information stored in the database
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DML Commands are…
INSERT INTO- inserts new data into database table
SELECT - extracts data from a database table
UPDATE - updates data in a database table
DELETE - deletes data from a database table
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DCL (Data Control Language)
• GRANT : gives user's access privileges to database
• REVOKE: withdraw access privileges given with the
GRANT command
TCL (transaction control language)
•Commit : save work done
•Rollback : restore database to original since the last
COMMIT
DQL (Data Query Language)
• select
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Data Storage and Querying
•A database system is partitioned into modules that deal with
each of the responsibilities of the overall system.
•The functional components of a database system can be
broadly divided into the storage manager and the query
processor components.
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 Storage Manager
•A storage manager is a program module that provides the interface
between the low-level data stored in the database and the application
programs and queries submitted to the system.
•The storage manager is responsible for the interaction with the file
manager.
•The storage manager translates the various DML statements into
low-level file-system commands. Thus, the storage manager is
responsible for storing, retrieving, and updating data in the database.
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The storage manager components include:
•Authorization and integrity manager: which tests for the
satisfaction of integrity constraints and checks the authority of
users to access data.
•Transaction manager: ensures that the database transaction
executions proceed without conflicting.
•File manager: which manages the allocation of space on disk
storage and the data structures used to represent information stored
on disk.
Buffer manager : which is responsible for fetching data from disk
storage into main memory.
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 The Query Processor
The query processor components include:
•DDL interpreter: which interprets DDL statements and records
the definitions
•in the data dictionary.
•DML compiler: A query can usually be translated into any of a
number of alternative evaluation plans that all give the same result.
The DML compiler also performs query optimization, that is, it
picks the lowest cost evaluation plan from among the alternatives.
•Query evaluation engine: which executes low-level instructions
generated by the DML compiler.
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• Data files: which store the database itself.
• Data dictionary :which stores metadata about the structure of
the database, in particular the schema of the database.
• Indices: which provide fast access to data items that hold
particular values.
Statistical database: A statistical database is a database used for
statistical analysis purposes.
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Application Architectures
Two-tier Architecture
•Database applications are usually partitioned into two or three
parts.
•In a two-tier architecture, the application is partitioned into a
component that resides at the client machine, which invokes
database system functionality at the server machine through
query language statements. Application program interface
standards like ODBC and JDBC are used for interaction between
the client and the server.
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Three-tier Architecture
•In a Three-tier architecture, the client machine acts as merely a front end
and does not contain any direct database calls.
•Instead, the client end communicates with an application server, usually
through a forms interface.
•The application server in turn communicates with a database system to
access data.
•The business logic of the application, which says what actions to carry out
under what conditions, is embedded in the application server, instead of
being distributed across multiple clients.
•Three-tier applications are more appropriate for large applications, and for
•applications that run on the World Wide Web(WWW).
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Advantages of 2-tier architecture:
•Understanding and maintenances is easier.
Disadvantages of 2-tier architecture:
•Performance will be reduced when there are more users.
Advantages of 3-tier architecture over 2-tier architecture
•Easy to modify with out affecting other modules
•Fast communication
•Performance will be good in three tier architecture.
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Database System Architectures
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Database Users and Administrators
There are four different types of database-system users,
differentiated by the way they expect to interact with the
system.
I.
Naive users
II. Application programmers
III. Sophisticated users
IV. Specialized users
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I. Naive users
•Users who interact with the system by invoking one of the
application programs that have been written previously.
•For example, a bank teller who needs to transfer $50 from account
A to account B invokes a program called transfer.
•This program asks the teller for the amount of money to be
transferred, the account from which the money is to be transferred,
and the account to which the money is to be transferred.
The typical user interface for naive users is a forms interface,
where the user can fill in appropriate fields of the form. Naive users
may also simply read reports generated from the database.
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II. Application programmers
•Application programmers are computer professionals who write
application programs.
•Application programmers can choose from many tools to
develop user interfaces.
•Programming languages that combine imperative control
structures (for example, for loops, while loops and if-then-else
statements) with statements of the data manipulation language.
•These languages, sometimes called fourth-generation languages
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III. Sophisticated users
•Sophisticated users interact with the system without writing
programs. Instead, they form their requests in a database query
language.
•They submit each such query to a query processor, whose function
is to break down DML statements into instructions that the storage
manager understands.
•Analysts who submit queries to explore data in the database fall in
this category.
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IV. Specialized users
•Specialized users are sophisticated users who write specialized
database applications that do not fit into the traditional dataprocessing framework.
•Among these applications are computer-aided design systems,
knowledgebase and expert systems, systems that store data with
complex data types .
•Example, graphics data and audio data.
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Database Administrator
•A person who has such central control over the system is called a
database administrator (DBA).
•A database administrator is a knowledgeable person who is
responsible for physical design and management of the database.
•In short the person responsible for defining, updating, and
controlling access to a database management system package.
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The functions of a DBA include:
•Schema definition: The DBA creates the original database
schema by executing a set of data definition statements in the
DDL.
•Storage structure and access-method definition: Define
Storage Structure
•Schema and physical-organization modification: The DBA
carries out changes to the schema and physical organization to
reflect the changing needs of the organization, or to alter the
physical organization to improve performance.
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•Granting of authorization for data access: Administrator can
decided which user can access the database data and what the
limitation of the different user for read and write a database data.
•Routine maintenance:
Periodically backing up the database
Ensuring that enough free disk space is available for normal
operations
Monitoring jobs running on the database and ensuring that
performance is not degraded by very expensive tasks submitted by
some users.
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