Ch 1: Your Future and Computer Competency - Content

1
3 / 12
CHAPTER
Databases
MIS105 Lec14 Irfan Ahmed Ilyas
2
Lecture Objectives

• Integrated File Approach for saving data
• Benefits/ Drawback
• Database Accessing Approach
• File based Programs
• DBMS based access
• Introducing DBMS
• Working of a basic DBMS
• Main DBMS Features
• Users in a DBMS Environment

3
Database Implementation Approaches

• Integrated File Approach
• Data is scattered among many different data files
• Each file is saving data relevant to its subject
  only
• Files are linked together through data pointers
  (common field values)
• The integrated collection of these data files is
  normally contained in one single disk file
  (database file)
• Disadvantage Cross-referencing across the files
  is needed for detailed reporting
• Benefit Data duplication is minimized which
  removes the updation anomalies

4
Integrated File Database Example

• A Student Grade Database
• STUDENT saving only student personal
  information
• GRADE_REPORT saving only grade information
  about student courses
• The process which decompose data optimally among
  data files is called Normalization.

5
Integrated File Database Example

• For detailed information, a cross-referencing
  activity is needed
• While reading GRADE_REPORT, other student details
  can be found by using the data pointer
  (StudentNumber) in the STUDENT file
• Data updation anomalies are removed
• Addition Anomaly While adding a new students
  grade in GRADE_REPORT file, no need to check for
  any data consistency .
• Deletion Anomaly Deleting all grades for any
  student, doesnt delete the student information
  from STUDENT file.
• Modification Anomaly A students attribute
  change in STUDENT file (like Name) doesnt need
  to be reflected in his grade records in
  GRADE_REPORT file (key attribute is an exception).

6
Accessing a Database

• Directly Accessing the database files
• Programs which directly work upon database files
  in order to
• handle data maintenance, like creating, defining,
  updating data, in files
• carry out the end-user job.
• Any high level language like C, Java etc. can
  be used to write such programs
• Disadvantages
• Structural Dependence
• These programs are very sensitive to the data
  file record structures
• A small change in the structure of any files
  record needs to change all the programs working
  over it.
• End users are always dependant on programmers for
  even a simple access to the database.

7
1. File Based Application Programs
Accounting End User
Registration End User
Other End Users
Accounting Application
Registration Application
Any other application.
8
Accessing a Database

• 2. Using DBMS Software
• DBMS Software is a collection of general purpose
  programs that enables users to create and
  maintain an integrated file database
• Separates the job of data maintenance from
  end-user use of stored data
• Available as a packaged software, called General
  Purpose Database Management System (DBMS)
• DBMS Main Features
• Data Structural Independence
• Different end-user applications can access
  database on disk through DBMS
• DBMS makes the applications unaffected with any
  structural change happened in database
• DBMS uses control information data (Data
  Dictionary) to inform the application programs
  about the structural details of the database
  files
• Data Dictionary is updated automatically by DBMS
  in case of any structural change done on the
  database

Chapter 11 (p268)
9
Example Data Dictionary
DBMS User
10
.. 2. Using DBMS Software

• .. DBMS Main Features
• Data Query Language
• DBMS lets its users/ application programs to
  access database by making use of some query
  language
• A query language is a set of standardized
  commands to perform different database
  maintenance activities
• SQL (Structured Query Language) is the most
  widely used.
• Examples of SQL commands are
• CREATE TABLE to create new data tables (files)
• SELECT to display selected data records
• UPDATE to modify selected data records
• and many others.

Chapter 11 (p295)
11
Details of DBMS Components

• Database Engine
• Controls all the data management activities (like
  database creation, retrieval, validation,
  manipulation etc.)
• DBMS Interface Objects
• Easy to use graphical interfaces (menus, buttons,
  wizards etc.) to access the underlying database
• Each of these objects are interacting with
  database engine in the background through SQL
  commands

12
A Look to Database Management Systems

• Create, modify, gain access to databases
• Subsystems
• DBMS engine
• Data definition subsystem
• Data dictionary
• Data manipulation subsystem
• SQL
• Application generation subsystem
• Data administration subsystem
• Database administrators

Chapter 11, pg294
13
A Working DBMS
DBMS Package
Programmers
Database Application
Programming Interface
End User
S Q L C O M M A N D S
Interface Objects
Database User/ Operator
Disk Storage
Integrated File Database
14
Database Personnel
Chapter 11 (p276)

• End Users
• Requires access to the database for their jobs
• Perform querying, updating and reporting on the
  stored database
• Usually provided with a user friendly application
  program interface
• Database Designers
• Identifying the logical/ structural database
  picture for an environment
• Database Administrators
• Controlling security, structural updates and
  performance issues for a corporate database
• System Analysts and Application Programmers
• Responsible for generating easy to use
  application programs for the end user requirements

15
Users in a DBMS Environment
End User
Database Designer
Database Administrator
Information System Application Program(s)
DBMS Modules
Data Definition Module
Data Manipulation Module
Database Creation Module
16
(No Transcript)