Ch 1: Your Future and Computer Competency Content

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CHAPTER
Databases
MIS105 Lec13 Irfan Ahmed Ilyas
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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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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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Data Organization in Databases
Character
Character
Character
Field
Record
Data File
A Database
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Data Organization Example

• In a University database

Field Name
Record for Ali
File Student
University Database
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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
• Drivers License
• Student ID Numbers

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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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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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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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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
• Students 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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.. 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 students number is modified, this needs a
  change in all other grade records of the same
  student (Modification Anomaly)

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