ForenameSurnameFormSubjectTeacherGrade HarrySmithAICTMiss BunceA FionaJonesBHistoryMr EvansB HarrySmithAHistoryMr EvansB JennyFieldsBArtMiss GoldA HarrySmithAArtMiss ColdA JennyFieldsAICTMiss BunceA What is the problem with this flat file database?
ForenameSurnameFormSubjectTeacherGrade HarrySmithAICTMiss BunceA FionaJonesBHistoryMr EvansB HarrySmithAHistoryMr EvansB JennyFieldsBArtMiss GoldA HarrySmithAArtMiss ColdA JennyFieldsAICTMiss BunceA 1.Data is duplicated – each exam entry requires the pupil data to be entered again 2.Data is inconsistent – mistakes are made 3.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
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 typeDescriptionExample IntegerWhole number4 or 5 or CurrencyNumber representing a financial amount £4.55 or $0.99 StringText or charactersJosh or 41 Bridge Street Date/timeDates or times in any format 15 th May 2010 or 14:56 or 09/12/2009 BooleanData which can only be one of two states Yes or no True 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