Organisation of Data for Effective Retrieval


Background:

In this section you should be able to:


What is a database?

Webopedia defines a database as:

 

A collection of information organized in such a way that a computer program can quickly select desired pieces of data. You can think of a database as an electronic filing system.

 

Traditional databases are organized by fields, records, and files. A field is a single piece of information; a record is one complete set of fields; and a file is a collection of records. For example, a telephone book is analogous to a file. It contains a list of records, each of which consists of three fields: name, address, and telephone number.

 

 


 

Types of databases: flat file vs relational

 

Flat file database: Disadvantages

 

Problem

Description

Examples

Data Inconsistency

The same data appears differently throughout the system.

Different software programs are used.

Changes to data made at different times.

John Smith in English database but J Smith in Mathematics database.

Updated every Thursday in English, every other Friday in Mathematics.

Data Redundancy

The same data is duplicated throughout the system.

Updates an enormous problem.

Errors are compounded.

Imagine John Smith in every school department.

Time is wasted.

Computer memory is inefficiently used.

Data Dependence

Any change in data format or structure requires a change in all the programs that access the data.

If John Smith changes form.

New entrants to school – all personal data in all databases.

Data lacks Integrity.

Can’t be trusted

Is inconsistently presented in various parts of the database.

Not always up to date.

Not always accurate

Database structure is inflexible

Difficult without lots of work to create reports using information from different databases.

Consider if all departmental databases are separate how would we get regular assessment data? – effort and attainment grades. In the past these were written onto lists and a clerical assistant spent days inputting them in – or the exercise was considered impractical.

 


Relational databases: structure



 

Relational Database Management System (RDBMS)


Advantage

Description

Examples

Single Centralised Store

Common data can be shared to all related tables within the organisation regardless of the software package you are using.

SIMS (Student Teachers Academic Records) can be shared in Assessment, Timetabling modules.

Data Redundancy is reduced if not got rid of.

Because there is only one copy of each attribute kept- duplication should be eliminated altogether in a well-designed RDBMS

Changes in personal details are changed in STAR only.

Data Independence

Each table can be administered without reference to other tables, although changes will take immediate effect within related information.

If a Department changes GCSE board this can be changed once in the Courses Table – as long as the Course ID remains the same?

Data Integrity.

Data should now be up to date, the same throughout, accurate and in general can be trusted.

Reports can easily be created with flexible layouts.

Easy to set up new relationships and new entities. New tables and reports can be set up as and when required.

Effort and Attainment grades can be entered centrally and shared wherever and whenever required.

Easier Security

All access to data is via a centralised system, a uniform system of security monitoring can be implemented

MIS is improved

Rather than concentrating on overcoming collection problems can now become creative in generating information.

Identify trends, exception reports, Model different scenarios.

 


Exercise:



Now do the questions at the end of Chapters 17, 18, and 19 of the text book