ForenameSurnameFormSubjectTeacherGrade HarrySmithAICTMiss BunceA FionaJonesBHistoryMr EvansB...
-
Upload
brandon-deem -
Category
Documents
-
view
217 -
download
0
Transcript of ForenameSurnameFormSubjectTeacherGrade HarrySmithAICTMiss BunceA FionaJonesBHistoryMr EvansB...
Forename
Surname Form Subject Teacher Grade
Harry Smith A ICT Miss Bunce
A
Fiona Jones B History Mr Evans B
Harry Smith A History Mr Evans B
Jenny Fields B Art Miss Gold A
Harry Smith A Art Miss Cold A
Jenny Fields A ICT Miss Bunce
A
What is the problem with this flat file database?
Forename
Surname Form Subject Teacher Grade
Harry Smith A ICT Miss Bunce
A
Fiona Jones B History Mr Evans B
Harry Smith A History Mr Evans B
Jenny Fields B Art Miss Gold A
Harry Smith A Art Miss Cold A
Jenny Fields A ICT Miss Bunce
A
1. Data is duplicated – each exam entry requires the pupil data to be entered again
2. Data is inconsistent – mistakes are made3. Difficult to add an extra field
Large collection of data items stored in separate tables with
links between them
e.g. – driving school has students, lessons and lesson types – all linked by the lesson table
e.g. – driving school has students, lessons and lesson types – all linked by the lesson table
You can view all the related data together
Data independence – data and programs stored separately. You can add an extra table and it won’t affect the programs.
Data consistency – data is only stored once – no danger of it being updated in one place and not in another
No data redundancy – data is not duplicated unnecessarily
More information available to users - all information is stored centrally – not in separate departments
Ease of use – queries etc. Data integrity – validation ensures
data is as correct as possible Greater security – authorised users –
different access levels
Complex and costly to set up Needs greater knowledge to set up Users require more training If data used for a range of
applications – security and confidentiality issues arise
Database is made of records – each record has a structure containing fields.
Data type Description Example
Integer Whole number 4 or 5 or 818809
Currency Number representing a financial amount
£4.55 or $0.99
String Text or characters Josh or 41 Bridge Street
Date/time Dates or times in any format
15th May 2010 or 14:56 or 09/12/2009
Boolean Data which can only be one of two states
Yes or noTrue or false
Query – a method of searching a database for specific information
Report – printed output from a database for a specific purpose
Form – an interface to a table or group of linked tables for data entry
Import – data from an external data source brought into the database
Export – data from the database used for another purpose – e.g. Mail merge letter
Fields can be coded – e.g. M or F Database can have validation Each record has a key field which is
a unique identifier