1. Databases ©

2. A database is a collection of data organised into a structured format.
What is a database?
Surname: James
First name: Samantha
Date of Birth:
Address: 16 Poppy Close
Town: Southam
County: Warwickshire
Surname: Brown
First name: David
Date of Birth:
Address: 16 Poppy Close
Town: Southam
County: Warwickshire
Surname: Lastler
First name: David
Date of Birth:
Address: 16 Poppy Close
Town: Southam
County: Warwickshire
Surname: Whitefield
First name: Nina
Date of Birth:
Address: 16 Poppy Close
Town: Southam
County: Warwickshire
A database is a collection of data organised into a structured format. ©

3. The word ‘Database’ is often linked to data held on a computer.
Paper based databases
Examples:
Telephone directory
Address book
Card index system
Details of car repairs
Customer returns book
The word ‘Database’ is often linked to data held on a computer. ©

4. Retrieving information
Main difference between paper and computerised databases is speed the data can be accessed.
Computerised databases make it possible to analyse data collected.
Shops – customer purchases
Health authorities – link illnesses to factors e.g. diet
Police – build up profiles of crimes/criminals ©

5. Flat files A flat file is a database held in a single file.
A spreadsheet can be used as a flat file database.
Video no.
Title
Country
Date released
Classification
Rental price 1
Lord of the Rings US
2001 12
3.50 2
Attack of the Clones
2002 PG
2.99 3
About a boy UK U 4
Crocodile Dundee
AUS
1986 15
1.50 5
Die another day 6
Shrek
1.99
Record
Field
File ©

6. Flat files - Uses Flat files are useful for:
Lists of contact names and addresses
Lists of student grades
Details of a video collection
However data stored in one flat file cannot easily be linked to data stored in another flat file. ©

7. Flat files - Problems
There are several drawbacks to holding anything except very simple data in a single flat file.
Have a look at the example and try to find some of the problems which exist with using a flat file as a database. ©

8. Redundant data There is a vast amount of repeated data.
This wastes disk space and slows the database down.
Data entry is time consuming ©

9. Errors on input
Typographical errors occur when data is entered needlessly.
This will affect the quality of the database and the results of queries and data analysis. ©

10. Problems with updating data
If Miss Smith gets married and changes her name, every record would have to be updated.
If a lecturer left and a new one was employed, every record for students taking that course would have to be updated. ©

11. Overcoming problems with Flat files
Not all of the data needs to be entered every time. Some of it could be moved to other tables and accessed when required.
Which data do you think could be moved to separate tables? ©

12. Using multiple tables
The student data could be moved into a separate table as follows:
Student ID
Student forename
Student surname
Date enrolled
Course code 1
Philip
Harris
30/08/2002
119 2
Michael
Jenner
09/09/2002
115 3
Ian
Bemrose
07/09/2002 4
Meena
Akbar
12/09/2002
118 5
James
Payne 6
Campbell
Naeve
12/10/2002
114 ©

13. Using multiple tables
The course data could be moved into a separate table as follows
Course Code
Course title
114
Physics
115
Chemistry
118
Applied Science
119 ©

14. Using multiple tables
The subject information could be moved into a separate table as follows
Subject ID
Subject Name
Day
Period
Lecturer ID 14
Physiology
Tuesday 3 1 15
Atoms 5 2 16
Electrons
Monday 4 17
Particles
Wednesday ©

15. Using multiple tables
The lecturer information could be moved into a separate table as follows:
Lecturer ID
Lecturer Name
Date employed 1
Meaner
03/11/1995 2
Maynard
01/02/2002 3
Noakes
09/10/1999 4
Smith
14/12/2002
A unique ID has been assigned to each lecturer, since if two people were hired with the same name, it would be impossible to distinguish between them. ©

16. Using multiple tables
Note that this structure does not currently allow students to take more than one subject.
In order to do that, another table will be required.
Student_subjectID
Student ID
Subject ID
001 1 14
002 15
003 2
004 3
005 16
006 4
007 ©

17. Problems solved Redundant data has been reduced.
Risk of errors reduced
Modifying and updating data problems resolved ©

18. Flat file information storage and retrieval systems
Read page 95 of Heathcote and write a paragraph explaining the advantages of a ‘database system’ over the ‘traditional file approach’ ©