St Andrew’s High SchoolStandard Grade Computing

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Databases

Standard Grade

Computing Studies

St Andrew’s High SchoolStandard Grade Computing

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Databases

DefinitionsA database is a structured collection of similar information which you can search through.

File A collection of structured data on a particular topic. A file is made up of records.

Record Information held about one person or thing. A record is made up of fields.

Field A single item of information.

St Andrew’s High SchoolStandard Grade Computing

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Types of Fields

Text holds letters, numbers and symbols

Numeric hold numbers for calculations

Date holds a date

Time holds a time

Graphic holds a picture

Calculated field performs a calculation on the contents of one or more fields.

St Andrew’s High SchoolStandard Grade Computing

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SearchingThe search facility allows you to look for information in the database.

A search may be:Simple Look for records with a match on one

field ( They have one thing in common.) eg Hair = “Brown”

Complex Look for records with a match on more than one item in one or more fields.Eg Hair = “Brown” AND Eyes = “Blue”

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Comparison operators< Less than< = Less than or equal to= Equal to> = Equal to or greater than> Greater than< > Not equal to

Contains

Eg. To find all records for 1st to 3rd year in a school database you could search for:

Year <= 3rd

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Credit

In a complex search we need to link the searches together using one of the following operators:

AND Both items required in each recordOR One item required in each record

Eg To search a school database for all Standard Grade Computing pupils you could search for:

Year = ‘3rd’ OR Year = ‘4th’ AND Subject = ‘Computing’

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Sorting

Sorting allows you to arrange the records in a database in alphabetic or numeric order. This can be ascending (A to Z or 1 to 9) or descending (Z to A or 9 to 1)

Sorting on More than one fieldWhen two items are the same in one field they can be separated using a second field for sorting.

For example, it is common to sort lists of names first by surname and then by first name

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Calculated Field(Also called a computed field). A calculated field allows you to carry out a calculation on another field or fields and return the answer in the calculated field. (similar to formulae in a spreadsheet).

Example: Field 1: Date of birthField 2: Today's dateField 3: Age

Field 3 is a calculated field and contains the formula: Today’s date - Date of birth

Other examples of calculated fields often used in reports include totals and sub-totals.

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ReportsAny information on your database that you print out is a report. You would normally do a search and / or a sort, and then select which fields you want to print.

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Size of a fieldThis is the total number of characters, including spaces, needed to hold the information in a field.

Eg. A Field containing the data‘Computing Department’

Would have a field size of 20

Examples of databases include:-Telephone directoryPolice National ComputerA personal Christmas card list

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Calculating the storage requirements of a database file

Field Size of field

1 302 43 254 245 66 37 28 6

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Field Size Bytes required1 30 302 4 43 25 254 24 245 6 66 3 37 2 28 6 6

Total for one record= 100 bytes

If a database has 50 records the storage space required=100 X 50 = 5000 bytes5000 / 1024 = 4.88 Kilobytes

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KeywordsThis is the text used to search a file for a particular entry.

Key FieldThis is a field which contains unique information for each record. That is, each record has a different number or text in the key field. Doing a search for an item on a unique field will only give one record.

Example: SQA has a database of all pupils attempting Standard Grade Exam. Each pupil has a unique candidate number because there will be more than one pupil with the same name and date of birth.

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Data Protection

Definitions:

Data User is a person who holds and uses personal data about others or controls the use of it.

Data Subject is a person about whom personal data is stored by a data user.

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The Data subjects have the following rights:

• to know if data is held about them on a computer

• to see a copy of this personal data

• to make corrections if necessary

• to ask for compensation if data is inaccurate or access given to an unauthorised person.

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Under the Data Protection Act (1984) data users must:• get and process the information fairly and

lawfully• register what reason they hold it for• hold only relevant information • hold only accurate and up to date information• not keep information any longer than needed• give individuals access to information about

themselves and, where necessary, correct or remove wrong information

• take appropriate security measures.

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Exceptions to the Act

There are exceptions to people’s right to see data held about them. The public are denied access to data held by the Police or security forces.

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Misuse of ComputersThe Computer Misuse Act is intended to protect all

types of information (not just personal) stored on computer systems.

HackingThis is the act of trying to gain unauthorised entry to files. This is done by using a wide area network and passwords.

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VirusesSome people enjoy writing and distributing computer viruses which destroy data and cause computers to crash or take up processor time in meaningless calculations. Viruses are usually spread by copying files (from unofficial sources).

To prevent viruses spreading:• Don’t share disks.• Don’t copy software.• Use an anti-virus program to check disks

regularly.

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Mail Merge

A database is the second general purpose package (along with a word processor) required to produce a mail merged document. Having studied both these packages, we are now in a better position to understand how a mail merge works.

Mail merging is the process of combining details from a database with a standard letter in a word processing package, to produce personalised letters - as many letters as there are records in the database.

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Name Flossie

Year S1

Name Josie

Year S5

Name Phyllis

Year S4

Database

Dear Parent,

I am pleased to inform you that your child ___________ has won a prize for the best Computing student in __________

Head Teacher.

Word Processed Standard Letter

Having created your database and your standard letter, you are ready to combine the two, filling the gaps in the standard letter with information from the database.

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The database field names are used to mark where in the standard letter information from the database will be inserted. These are shown in brackets like so << >> to mark them.

Dear Parent,

I am pleased to inform you that your child <<Name>> has won a prize for the best Computing student in <<Year>>

Head Teacher.

Word Processed Standard Letter with database fields inserted ready for mail merge.

When the mail merge is performed the field names in brackets are replaced with the appropriate fields from the database. This is done for every record in the database.