1. 3 / 12 Databases MIS105 Lec13 Irfan Ahmed Ilyas CHAPTER Prepared By:
Mr. S. A. Raza
Mr. Irfan A. Ilyas
Delivered in:
Week #1 (26 – 30 Jan, 2002)

2. Prepared By: Irfan Ilyas
Lecture Objectives
Database Concepts
Data Organization in databases
Key Field
Main activities in Database Maintenance
Defining data
Creating data
Manipulating data
Database Usage
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Prepared By: Irfan Ilyas

3. Prepared By: Irfan Ilyas
Database Concepts
A database is a structured collection of related data, stored in some medium for some specific purpose.
A database usually represents some real world environment, thus reflecting changes happening in that environment.
Examples:
Addresses/ telephone numbers stored in some indexed address book
Course related data saved on a computer disk using some software like Microsoft Excel, Microsoft Access etc.
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Prepared By: Irfan Ilyas

4. Data Organization in Databases
Character
Character
Character
Field
Cha..
Field……
Cha..
Field
Record
Data File
Record
:……….
Data File
………..
A Database
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Prepared By: Irfan Ilyas

5. Data Organization Example
In a University database A L I
Field: ID …
Field: Score
7 0
Field: Name
Record for Ali
File: Student
Record for Rasheed
Record for …
University Database
File: Course
File: Faculty
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Prepared By: Irfan Ilyas

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A Database Example
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….Database Concepts
Key Field
Searching a particular record uniquely in a data file requires at least one field unique in value for all records
Example, in STUDENT file StudentNumber is such a field
Common example of key values (in daily life databases)
Social Security Number
Driver’s License
Student ID Numbers
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Prepared By: Irfan Ilyas

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Electronic Databases
Databases on some electronic media like disks
Computer programs are needed to maintain/ use on disk databases
Three main activities for electronic database maintenance
Defining
Specifying the data types, data validation rules etc. for the data values
Creating
Storing the data values (as defined by the user) on some physical medium
Manipulating
Querying/ searching/ updating the data values
Checking the conformance with the defined data constraints (validation rules)
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Prepared By: Irfan Ilyas

9. Prepared By: Irfan Ilyas
Database Usage
Databases are mostly used as an integral part of related Information Systems
Accounting Staff
Registration Staff
Accounting Information System
Registration Information System
A shared database in a University environment
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Prepared By: Irfan Ilyas

10. Database Implementation Approaches
Flat File Approach
Every data file is tried to be rich in all the relevant details
Every data file is used on a localized basis (e.g. one file for each department).
This makes every file independent of the other files in the database
Benefit: Data Reporting is easily done on each file independently
Disadvantage: Data inconsistencies may result due to data redundancies (duplications)
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Prepared By: Irfan Ilyas

11. Prepared By: Irfan Ilyas
A Flat File Database
A Student Grade Database
All the information needed is placed in one single data file
For example, a spreadsheet containing a single student grade file
No need to refer to any other file for data reporting
Redundant data values
In GRADE_REPORT:
Student’s personal information includes:
StudentNumber, StudentName, Class, Major
Whenever a grade record for a student is inserted in the file, his personal information is repeated.
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Prepared By: Irfan Ilyas

12. .. A Student Grade Database
Possible Data Updation Anomalies (abnormality)
When adding a grade for an already existing student, his personal information needs to be consistent with the existing ones (Insertion Anomaly)
If all grade records for a specific student are deleted, other details for that student will also be lost (Deletion Anomaly)
If any student’s number is modified, this needs a change in all other grade records of the same student (Modification Anomaly)
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Prepared By: Irfan Ilyas

13. Prepared By: Irfan Ilyas
02/3/2002
Prepared By: Irfan Ilyas