Database Management System

Data Storage Hierarchy

Database: Student’s File Contains Several
Teacher’s File file
Staff’s File

File: Result File

Name CGPA Add. Contains several
Arian 3.50 Dhaka record
Brown 3.80 Khulna

Record : Name: Arian Contains several

CGPA: 3.50 fields
Address: Dhaka

Field: Name field Contains several

Arian characters
Byte : Letter A Consists of 8 bits
01000001
Bit (0,1)
 Database & Database Management
System?
• Database is a large collection of stored, integrated file
that can be manipulated.
• A database management system is a computer based
system for defining, creating, manipulating,
controlling, managing, and using database.
• Database management system are replacing old file
management systems and thereby improving data
integrity and independence and reducing data
redundancy.
• Example: MS-Access, Oracle, MySQL, MS SQL
Server, PostgreSQL
Traditional File Management System

Course grade file Student Record File Tuition billing file

Student ID Student ID
Student ID Name Name
Name Address Address
Address Misc. Student Amt. Paid
Grades data Amt. owed

Periodic Report
Periodic
grades For
Billing
report alumni
Statement
students
 Database Management System
Course grade file Student Record File Tuition billing file

Student ID Name Name Student ID

Address Address
Grade Student ID Amt.paid
Name Amt.owed
Address
Misc. Stu.
data

Periodic Report Periodic

grades For Billing
report alumni Statement
students
 Limitations of Traditional File
Management System
• Data Redundancy
• Data Inconsistency
• Lack of Data Integration
• Program Dependence
• Data Dependence
• Limited Data Sharing
• Poor Data Control
• Problem of Security
• Inadequate data Manipulation Capability
 Advantages of DBMS
• Flexibility
• Fast response to information requests
• Multiple access
• Lower user training costs
• Less storage
 Disadvantages of DBMS
• Complex
• Vulnerability (Risk of critical data loss)
• High cost for small enterprises
• Improper use and incorrect decision
• Security problem
 Fundamentals of DBMS
Database management systems need large storage
capacities, usually supplied by magnetic tape, hard
disk packs, CD-ROM, and mass storage systems.
DBMS software usually includes
1. a query language,
2. a report writer,
3. utilities,
4. a data dictionary and
5. a transaction log.
 Query Language
• A query language is an easy –to-use computer language that
provides access to data in database

• The objective of the query language is to provide users with

simple, natural language structure to select record from a
database and produce information on demand

• For example, take request for inventory information.

 DBMS Software

Query: How
many items in stock?
DBMS retrieved
information from
product line
Database Management System Software

1. Query Languages
2. Report Writer
3. Utilities
DATABAS
E

Payroll Personal Product

File File File
 Query language in SQL
• DDL (Data Definition Language)
- Defines the structure of the database
- Deals with the whole database
- Example: Create Database, Alter Database, Drop
Database
• DML (Data Manipulation Language)
-Perform operations on the database
-deals with individual record
Example: Insert data, delete data
 Report Writer
• The report writer aspect of DBMS software
simplifies the process of generating reports after
querying the DBMS system of information
• The procedure is fairly easy
• Report headings, column headings for the items to
be included in the report as well as any tools,
subtotals, or other calculations are easily specified
• The report form can then be saved for future use
 Utilities
• Part of the DBMS software, used to maintain the database on
an ongoing process
• Includes:
Creating & maintaining the data dictionary
Deletion
Protecting the database from unauthorized use
Provides an easy way to recover data when the database is
damaged
Preventing data corruptions when multiple users attempt to
use the same database simultaneously
Recognizing the data in the database into predefined sort
order to make access quicker
 Data Dictionaries
• Essentially a small database with information about the data
& data structure of a database
• It contains metadata i.e. data about data
• Data dictionary maintains standard definitions of all data
item including
What data are available
Where the data are located
Data attributes (Description)
Who owns or is responsible for the data
How the data are used
Who is allowed to update or change the data
Security & privacy limitations
 Transaction Logs
• Contains a complete record of all activities for
mini computer
• Systems for mini computers & mainframe
usually build the transaction log automatically
• Important in reconstruction of the data base
after a failure and in prevention & detection of
unauthorized access.
Data Dictionary & Transaction log

DBMS
Data
Query dictionary
Location of data in
database are
determined
Transaction
log ( records
current
Database activities)

Answer
to
query
 Types of Database Organization
• Common database structure are
1.Hierarchical Model
2. Network Model
3. Relational Model
4. Object oriented Model
 Hierarchical DBMS
• Fields or records are arranged in related groups
resembling a family tree, with “child” records
subordinate to “parent” records
• A parent may have more than one child, but a
child always has only one parent
• To find a record, you have to start at the top
with a parent & trace down the chart to the
child
 Hierarchical Database Model
A cruise ship reservations system

Parts of Los
departure Miami New York
Angeles

Names The love

QE 2 The Oriana
Of Ships Boat

Sailing May 30 July 15

April 15
dates

Cabin A-1 A-2 A-3

number
 Network DBMS Model
• Similar to hierarchical DBMS, but each child
record can have more than one parent record
• A child record may be reached through more
than one parent
• More flexible than the hierarchical one
• Still requires that the structure to be defined in
advance
• There are limits to the number of links that can
be made among records
 Network Database Model
A college class scheduling system

Accounting Finance Marketing

Courses
101 200 210

Instructor Al-Amin Shah Alam Mahadi

Students Student A Student B Student C Student D Student C

 Relational Database Model (RDBMS)
• Relates or connects , data in different files through the use of key field or
common data element
• No access path down through the hierarchy
• Data elements are stored in in different tables made up of rows & columns
• Related table must have a key field that uniquely identifies each row
Advantages:
- User doesn’t have to be aware of any structure
- Can be used with little training
- Entries can be easily added, deleted or modified
Disadvantage:
- Searches can be time consuming
- Costly
 Relational Database Model
A state department of motor vehicles database

Driver’s Street City State Zip Drivers Expiration

Drivers
Name Addres licenses date
License file/ table
s number

Car owner Car Car Driver’s Street City State Zip

file license make & name address
number year

Citation Moving Date Cited Driver’s Fines

Moving violation
number Validation licenses paid/ not
Citation file
type number paid

Parking violation Citation Parking Date cited Car license Fines paid/
Citation file number violation number not paid
type
Relational Database Model
 Object-oriented database model
An object oriented model or object-relational
database management system (ORDBMS), is
a database management system similar to
a relational database, but objects, classes and
inheritance are directly supported in database
schemas and in the query language.
Object-oriented database model
 Entity-Relationship Model

A semantic model that captures meanings and intents.

E-R modeling is a conceptual level model Proposed by
P.P. Chen in 1970s.

• Entities are real-world objects about which we collect

data
• Attributes further describe the entities with particular
values
• Relationships are associations among entities
• Entity set – set of entities of the same type
• Relationship set – set of relationships of same type
 Entity-Relationship Model
SYMBOL
Entity-Relationship Model
 Designing a Database
• Database design is done to meet both logical
and physical organization need
• Logical design refers to what the database is
(What is in it)
• Physical designs refers to how the data is
organized and stored & what storage
hardware is used
 Logical Design
• Refers to what the database is , not how it operates
• Is a detailed description of the database model from the
user perspective rather than the technical perspective
• Involves defining user information , needs, analyzing
data element requirements and logical groupings
considering input & output methods, finalizing the
design, & creating the data dictionary
• Focus is on identifying every element of data necessary
to produce the required information systems reports
and on the relationship among the record
 Physical Design
• Specifies exactly how the data will be arranged &
stored on the direct access storage devices
allocated for DBMS
• Objective is to store data so that it can be updated
& retrieved as quickly and efficiently as possible
• DBMS users are not involved in physical design
of DBMS, since that is determined by the type of
DBMS software they have purchased for their
micro computers or running on a large scale
computer
 Database Administration
• The effective use of database within an organization requires a great
deal of cooperation and coordination

• User requirement and needs throughout an organization need to be

frequently reviewed & overall security and integrity of database
must be ensured

• Organizations working with DBMS need a database administrator

(DBA) , an individual or group of individuals to coordinate all
related database activities and to control the database

• Organizations usually appoint a database administrator to manage

the database & and related activities.
 Jobs of the DBA
1. Database design : Plays a key role in both logical and the physical design
2. Database implementation & operation: guides the use of the
DBMS on a daily basis
3. Coordinating with user : Receives & reviews user requests for
additional BDMS support that have been forwarded by programming analysts
4. Backup & recovery : responsible for preparing plan to periodically back
up database(s) and for establishing procedures for recovery from the failure of the
DBMS software or related hardware
5. Performance Monitoring: constantly monitors the performance of the
DBMS using specializing software to calculate and record operating statistics
6. System Security : responsible for designing & implementing a system that
controls user’s access to the database files and determines which DBMS operation
can be performed , as well as which application programs can be accessed
Thank you !