Lecture 1: Introduction to Database - Nubacad.com

MIS 4102 :
Database Management Systems
Md. Zahidul Hasan
Lecturer
Dept. of Computer Science and Engineering
Northern University Bangladesh
Lecture 1
Introduction to Database
Management System
Data and Information
• Data – A collection of raw facts and figures.
Data is an encoded representation of
information.
• Information – Final product created from the
raw data after processing. So, Information is
summarized data or otherwise manipulated
(processed) data.
• Information systems process and manage
data. Data Management involves
“Capturing”, “Retrieval” and “Storage” of
data.
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• A database is collection of data, or
information that is organized so that specific
information can be easily located and
retrieved.
Examples:
• Phone book
Database
• University grading system
• Airline reservation system
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Database Management System (DBMS)
• A database management system (DBMS) is an
integrated collection of programs that are used
to create and manage information in a database.
• Examples:
• Microsoft Access
• Oracle
• SQL Server
• MySQL
• DBMS contains information about a particular
enterprise.
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Database Management System (Cont…)
• Four basic functions performed by all DBMS
are:
• Create, modify, and delete data structures, e.g.
tables
• Add, modify, and delete data
• Retrieve data selectively
• Generate reports based on data
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Database Management System (Cont…)
• Database Applications:
• Banking: transactions
• Airlines: reservations, schedules
• Universities: registration, grades
• Sales: customers, products, purchases
• Online retailers: order tracking, customized
recommendations
• Manufacturing: production, inventory, orders, supply chain
• Human resources: employee records, salaries, tax
deductions
• Databases touch all aspects of our lives
Why Use a DBMS
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Past System for Managing Information
The File Systems Approach
• The information is stored in permanent system files.
• A number of application programs are written to
manipulate the files.
General
Ledger
File
Production
Planning
File
Invoicing
File
Despatch
File
Personnel
File
Payroll
File
Inventory
File
Order
Entry
File
Sequential Files
File Organisation
• records are stored in a fixed sequence
• records can only be read in that sequence, starting from
the first record
• records can only be added at the end of the file (append)
• sequential files are not efficient
Indexed Files
• Use an index to access records in a random fashion.
• Records can be sorted according to an attribute or
preference. (e.g Alphabetically, Ascending, Descending,
etc.)
• Indexed files are efficient, and faster to access.
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Disadvantages of File Processing System
• Data Redundancy: Data Redundancy means
same information is duplicated in several files.
• Data Inconsistency: Data Inconsistency means
different copies of the same data are not
matching. That means different versions of same
basic data are existing. This occurs as the result
of update operations that are not updating the
same data stored at different places.
• Example: Address Information of a customer
is recorded differently in different files.
Disadvantages of File Processing System (cont..)
• Difficulty in Accessing Data: It is not easy to
retrieve information using a conventional file
processing system. Convenient and efficient
information retrieval is almost impossible using
conventional file processing system.
• Data Isolation: Data are scattered in various files,
and the files may be in different format, writing new
application program to retrieve data is difficult.
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Disadvantages of File Processing System (cont..)
• Integrity Problems: The data values may need to
satisfy some integrity constraints. For example the
balance field Value must be grater than 5000. We
have to handle this through program code in file
processing systems. But in database we can declare
the integrity constraints along with definition itself.
• Atomicity Problem: It is difficult to ensure atomicity
in file processing system.
• Example: transferring $100 from Account A to
account B. If a failure occurs during execution
there could be situation like $100 is deducted from
Account A and not credited in Account B.
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Disadvantages of File Processing System (cont..)
• Concurrent Access anomalies: If multiple users
are updating the same data simultaneously it will
result in inconsistent data state. In file processing
system it is very difficult to handle this using program
code. This results in concurrent access anomalies.
Security Problems: Enforcing Security Constraints
in file processing system is very difficult as the
application programs are added to the system in an
ad-hoc manner.
• Database systems offer solutions to all the above
problems.
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The Database Approach
Advantages of using a Database Approach
General
Ledger
Production
Planning
Invoicing
Despatch
Personnel
Payroll
Inventory
Order
Entry
• Flexible Data Access: Database Management Systems
have various tools to manipulate, query, or report data,
such as Structured Query Language (SQL), and Report
Generators. Hence:
• Selected data is easily retrieved
• A DBMS can contain different data views for different
users
• Improved Data Integrity: Modern DBMS consist of
various tools and methods to:
• ensure that data is correct, consistent, and current
• verify data input and check whether data is
„reasonable‟.
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Advantages of Database (Cont…)
• Improved Data Security: Tools such as password access, and
encryption, ensure that data is not:
• deliberately or accidentally damaged or changed
• accessed without proper authorisation
• Data Independence
• Problems occurs from the interdependence of data and
programs are kept to a minimum.
• Reduced Data Redundancy
• Efficient data storage.
• Relational Databases use Normalisation to reduce data
redundancy.
Advantages of Database (Cont…)
• Ability to Share and Relate Data
• Different user groups can use the same data.
• Data in different (physical or logical) parts of the system can
be related for a certain application.
• Increased Productivity
• Centralized Control
• Enhancement of Data Quality
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Costs of Database Approach
Levels of Abstraction
The implementation and use of DBMS is normally
associated with various costs. Such as:
• Initial expenses involve planning costs, and
consultancy fees.
• Computer hardware costs.
• Software costs.
• Database Administrator costs, and staff training
costs.
• Conversion costs of an existing system.
• Various operational costs.
There are three levels of
abstraction for database
design:
1. Physical or Internal level
2. Logical or Conceptual level
3. View or External or User
level
View 1 View 2 View 3
Logical level
Physical level
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Levels of Abstraction (cont…)
1. Physical or Internal level
The lowest level of abstraction describes how the data are actually
stored. Complex low-level data structures and access methods
are described in detail.
2. Logical or Conceptual level
The middle level describes what data are stored in the database,
and what relationships exist among those data. The entire
database is described in terms of a small number of relatively
simple structures.
3. View or External or User level
The highest level of abstraction describes only part of the entire
database of concern to a user or application program. application
programs hide details of data types. Views can also hide
information (e.g., salary) for security purposes.
The system may provide many views for the same database.
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• Conceptual schema:
Example: University Database
• Students(sid: string, name: string,
login: string, age: integer, gpa:real)
• Courses(cid: string, cname:string,
credits:integer)
• Enrolled(sid:string, cid:string,
grade:string)
• External Schema (View):
• Course_info(cid:string,enrollment:integer)
• Physical schema:
• Relations stored as unordered files.
• Index on first column of Students.
View 1 View 2 View 3
Conceptual Schema
Physical Schema
DB
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• Instance
Instances and Schemas
Database change over time as information is
inserted and deleted. The collection of information
stored in the database at a particular moment is
called an instance of the database.
[
• Schema
The overall design of the database is called the
database schema.
Database systems have several schemas,
partitioned according to the levels of abstraction. At
the lowest level is the physical schema; at the
intermediate level is the logical schema; at the
highest level is the subschema.
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Data Models
A data model is a collection of concepts for
describing data and data relationships.
•Entity-Relationship model
•[
•Relational model
•Other models:
object-oriented model
semi-structured data models (XML)
Older models: network model and hierarchical
model
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Entity Relationship Model
Models an enterprise as a collection of entities and
relationships.
Entity: a “thing” or “object” in the enterprise that is
distinguishable from other objects. Described by a set of
attributes.
Relationship: an association among several entities.
Relational Model
The relational model uses a collection of tables to represent
both data and the relationships among those data.
Each table has multiple columns, and each column has a
unique name.
teacherID
name
courseNo
title
teacher
conduct
course
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Object oriented Data Model
• Current generation systems have a need to handle
complex data for complex applications such as -
• computer aided design
• computer aided software engineering
• geographic information systems
• interactive web sites
• Object oriented databases are well suited to
handling graphics based or multimedia applications.
Can Stores objects (documents, multimedia, Image,
Video).
Semi-structured data models -
Extensible Markup Language (XML)
• Defined by the WWW Consortium (W3C)
• Originally intended as a document markup
language not a database language.
• The ability to specify new tags, and to create
nested tag structures made XML a great way to
exchange data, not just documents.
• XML has become the basis for all new generation
data interchange formats.
• A wide variety of tools is available for parsing,
browsing and querying XML documents/data.
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Hierarchical Model
• Stores data as hierarchically related to each other.
Record shape are tree structure.
• Logically represented by an upside down tree
• Each parent can have many children
• Each child has only one parent
NUB
Network Model
A network database is similar to hierarchical DBMS, but
each child record can have more than one parent record.
Thus a child record may be reached through more than one
parent.
University class scheduling system
CIT 1101 CIT 3303 MIS 4102
Faculty of
Science
Faculty of
Business
SMR BA ZH
CSE
CS
BBA
MBA
Student 1 Student 2 Student 3 Student 4 Student 5
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DBMS Languages
• Data-Definition Language (DDL) : DDL concerned
with defining the structure of the database.
• Data-Manipulation Language (DML): DML
concerned with querying and manipulating the data
in the database. They are basically two types:
• Procedural DMLs: Procedural DMLs require a
user to specify what data are needed and how to
get those data.
• Nonprocedural DMLs: Nonprocedural DMLs
require a user to specify what data are needed
without specifying how to get those data.
Goals of Database Design
It is important to design the database in such a way
that:
• A specific item can be reached easily
(maximum guarantee that the desired record will be reached)
• The database can respond to the user’s different questions
easily (necessary relationships are provided)
• The database occupies minimum storage space (choosing
data types and how to express a certain concept is important)
• The database contains no unnecessary data
(storing the gross salary is enough, the net salary can be
calculated from the gross salary)
• Data can be added and updated easily
without causing mistakes (no data redundancy)
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Steps in Database Design
• Requirement analysis
What does the user want
• Conceptual database design
Defining the entities and attributes, and the
relationships between these --> The ER model
• Physical database design
Implementation of the conceptual design using a
Database Management System
Any Question
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Thanks to All
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