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Computing and Information Science

Databases

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Computing and Information Science

What is a Database

•A database is acollection of data.

•The data that iscollected can beorganised for aparticular purpose

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Fields

In a database, a field is one piece of information about aperson or thing. For example, a database about pupilsmight have the following fields:

•Forename

•Surname

•Form class

•Date of birth

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Records

In a database, a record is all the information whichrelates to one person or thing. So if we look at a schooldatabase, all the information about one pupil (forename,surname, date of birth and form class) would be onerecord in the database.

Or, if you look at the phone book, thename, address and telephone numberfor one person is a record.

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Files

In a database, a file is the entire collection ofinformation. In a school database, this would be therecords on all the pupils in the school

Or, if you look at the phone book, theentire book would be the file.

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Summary of Structure

If we think of a database as a table of information, thenwe can identify the structure as:

 FIELD is a column

 RECORD is a row

 FILE is the complete

table

Fields

Records

File

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Searching

A simple search

is a search where you are only looking for one value onone field, e.g. surname = Jones.

A complex search

is when you are searching for more than one thing

-either on different fields (e.g. surname = Jones andforename = Brian),

-or for different values in the same field (e.g. surname =Jones or surname = Smith).

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Search Operators

Search operators are used to help specify the records weare searching for. Common examples are:

•Equals (=)

•greater than (>)

•less than (<)

•highest or lowest value

If you are carrying out a complex search, the searchcriteria can be linked by using AND or OR. Using AND willfind records meeting both criteria only, and using OR willfind records meeting either of the criteria specified.

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Sorting

Sorting simply means putting the database into order, eitherascending (A – Z,

1 – 100) or descending (Z – A, 100 - 1). A sort on one field of thedatabase (e.g. surname or date of birth) is known as a simplesort.

Surname

Forename

Smith

William

Smith

Thomas

Smith

Abigail

Thomson

Fred

Thomson

Julie

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Sorting

A complex sort is when the database is sorted on more than onefield, e.g. sorted in order of surname and forename. This means thatif there is more than one record containing the same surname thenthey will be sorted by forename.

Surname

Forename

Smith

Abigail

Smith

Thomas

Smith

William

Thomson

Fred

Thomson

Julie

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Editing a Database

A database that has been created can be editedby either adding or deleting records or adding ordeleting fields.

Adding a field allows more data to be stored.

For example adding the date of births to amembers club database.

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Creating a Database

Before creating a database it is very important to design which field namesand field types are to be used.

Common field types used are.

Text :Any field which contains letters and numbers

Number: Any field which contains only numbers

Date/Time:Any field which contains a date or time

Boolean (Yes/No):A field which contains only two values eithertrue/false or yes/no

There are other field types available but these are the most commonlyused.

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Creating a Database

The length of each field is also important.

The database should not have too much room for set aside but also cannotuse too little.

For example:

A database may hold chefs names, including Ken Hom and Marco PierreWhite.

For the forename field we will need to have at least 5 characters for the chefsgiven (Ken and Marco) but there may be chefs with longer forenames so weshould perhaps set aside 10 characters for forename.

For the surname field we will need to have at least 12 characters for thechefs given (Hom and Pierre White, a space is counted as a character) butthere may be chefs with longer surnames so we perhaps should set aside 20characters.

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Altering Output Format

You can alter the output format of your database bychoosing which fields/records will appear either on themonitor or on a printout, for example:

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Reporting

One of the most powerful features of database packages isthe reporting feature. This allows you to use any part ofyour database to create a printed report on a specific area.Reporting allows you to:

Select which fields you want to appear

Select which records you want to appear

Select the order in which the records appear

Include calculations on the data

Add text and formatting to the such as report

headings, underlining, page numbering and so on.

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Creating a graphic field

Creating a graphics field allows pictures to be included intoyour database.

This is an important feature, making databases moreinformative.

For example the passport office, police and customs wouldall make use of databases like these.

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Creating a Computed Field

A computed field is a field type which involves a calculation.

The data the field contains is calculated using the values ofdata in other fields of the record.

For example a record might consist of 4 fields.

Name of product:Text

Cost Price:Number

VAT:Number

Total Cost:Calculated (Cost Price + VAT)

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Calculating Storage Requirements Example

Here is the design for a simple school database whichcontains 300 records.

The storage required for one record:

20 + 20 + 4 + 40 + 15 = 99 bytes

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Calculating Storage Requirements Example

There are 300 records in the database, so the totalstorage space required is:

99 x 300 = 29 700 bytes

We can convert this to kilobytes by simply dividing thetotal by 1024:

29 700/1024 = 29kb

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Multimedia Databases

Many CD-Roms contain information stored in a database. Forexample, a multimedia encyclopaedia is essentially a database ofarticles. These databases usually have a search tool that allows youto find articles containing keywords.

Find articles including the phrase “World War One”

It is also possible to do more complex searches involving severalkeywords using AND, OR and NOT

Find articles including the words “World War One” OR “FirstWorld War”

It is also possible to search web pages in the same way using aSearch Engine such as google or altavista

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Data Protection Act (1998)

The Data Protection Act (1998) became law on 1st March 2000. Itgoverns the processing and storage of personal information held byorganisations/businesses/schools on computer. It also governs somepaper records.

If an organisation is going to store data about people, it has to registerthis intention with the Data Protection Commissioner, who keeps apublic register. This register stores the name and address of the datacontroller, and a description of the processing being carried out.Individuals can consult the register to find out what processing isbeing carried out. The data subject must also be aware of the databeing stored and for what purpose.

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Data Protection Act - Principles

The following definitions apply under the Data ProtectionAct:

•Data Subject –

•The person whom the information is about.

•Data Controller –

•The organisation collecting and controllingpersonal information

•Data User –

•Someone authorised by the Data Controller(eg an employee) to use the personalinformation

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Data Protection Act - Principles

Personal information must be:-

Obtained and used fairly andlawfully.

Only used for specified purposes(the purpose must be specifiedprior to obtaining the data).

Adequate, relevant and notexcessive.

Accurate.

Processed in accordance with thedata subject’s rights.

Secure.

And must not be:-

Kept longer than necessary,

Transferred to countrieswithout adequate protection.

There are 8 data protection principles:

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•To see personal information being held about you (right ofsubject access).

•To prevent processing likely to cause substantial damage ordistress (not in all cases).

•To prevent processing for the purposes of direct marketing.

•To take action to rectify, block, erase or destroy inaccuratedata.

•To ask Commissioner to assess whether the Act has beencontravened.

•To take action for compensation if damage or distress iscaused.

Under the Data Protection Act, a Data Subject has thefollowing rights:-

Data Protection Act - Definitions

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Computer Misuse Act (1990)

The Computer Misuse Act (1990) was made to try toprevent unauthorised access to computers, otherwiseknown as hacking. Under the Act, it is illegal to:

•Gain unauthorised access to a computer, itsprograms and its data;

•Gain unauthorised access to a computer, itsprograms and its data with the intent to commit afurther offence;

•Modify computer material after gainingunauthorised access - this includes hardware,programs and data.

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This act gives people certain rights over work they do. Itcovers books, music, films and computer programsamong other things. The act makes it illegal to

•Create copies of work (e.g. pirate software, copymusic CDs and DVDs)

•Use illegally copied materials (e.g. listening topirated CDs)