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Databases What is a Database? A database is a way of storing a collection of related information A database could be manual but it is usually computerised Who would use a Database? Police criminal records database Hospital patients database DVLA database Library database Directory Enquiries database Examples of Manual Databases Telephone Directory Dictionary Encyclopaedia Atlas Diary Filing Cabinet A Database of Videos Name of film Starring Video Number Certificate Category Braveheart Mel Gibson 1578 15 Historical Epic VIDEO FILE Titanic Leon Liar Liar Jim Carrey Star Wars Ewan 157 MacGregor 4574 12 4657 Dra 12 U Comedy Sci Fiction File, Record, Field A database contains many files Each file contains many records Each record contains many fields VIDEO File BRAVEHEART Record CATEGORY Field A field is a single piece of information about a person or thing in a record. A record is a collection of related fields about a person or thing A file is a collection of records grouped together. Advantages of using a Computerised Database Speed of access Reliability Less storage space Easy to add, amend, delete records The database can be sorted and searched Selected information can be printed Disadvantages of a Computerised Database Hardware and Software must be purchased Training must be given Database must be maintained Features of Database Packages A database is a GPP It has all the features of any GPP – eg Load, Print, Save, Amend, Delete In addition a database allows you to Add, amend or delete records Search and sort records Types of Field Text – only letters eg abc, ABC Numeric – only numbers eg 123, 890 Date – a formatted date eg 12/12/02 Time – a formatted time eg 1500 hours Graphic – a picture eg Searching the Database Records can be searched for particular information You can do a complex You can do a simple search – searching on search – searching two or more fields on one field Once you have performed your search all the records which match the search conditions are displayed. You could search a database of criminals for those over a certain height. Sorting the Database Sorting allows you to sort the records in the database in a particular order. A database of bank customers could be sorted in ascending order on the field ACCOUNT NUMBER A database of employees could be sorted alphabetically on the field SURNAME More on Sorting The database could be sorted on one field – eg SURNAME The database could be sorted in ASCENDING or DESCENDING order The database could be sorted on 2 or more fields - eg SURNAME and FORENAME The database can be sorted in any order. This allows the user to view the records in the order most suited to their needs. Creating a Database Decide on your field names Decide on your field type Decide on your field size or length (remember spaces count as characters) Add your data or records Save the database with an appropriate name Reports The information you print from the database is called a Report. Before you can print a Report you must set up a Report Definition. You must decide What fields you want to include in your report What order you want the fields printed in Computed Fields Computed or Calculated fields carry out a calculation on another field (s). What goes into a Computed field is calculated by the computer and not inserted by the user - similar to what happens in a spreadsheet. For example Total Cost less Balance Paid could be the formula in the Amount Due field. The computer would perform the calculation and enter the amount in the Amount Due field. Altering Record Format You can display the information in the database in different ways. You can alter what you see on the screen (input format) and how your Report looks (output format) Examples of different formats are: Table List Columns Calculating the Storage Requirements It takes 1 byte to store 1 character To store a name with 20 characters takes 20 bytes To store an address with 50 characters takes 50 bytes To calculate storage space required for one record add up the length of each field and you will have the total number of bytes for each record To calculate the storage space required for the whole database multiply the record storage requirements by the number of records Commercial Databases Many companies used database to build up customer profiles These databases can then be sold or exchanged with other companies The customers details can be used to send mail shots or junk mail using standard letters and mail merge Often people do not know their details are stored on a database Personal Privacy With all this information potentially changing hands some people are very worried that information about them could be accessed. What if the data held about YOU was incorrect or out of date. How might it affect you? The Data Protection Act has been brought in to protect people and their personal data. The act was introduced in 1984 and updated in 1998. The Data Protection Act The parties involved Data Controller (the holder of the information) Data Processor (the processor of the information) Data Subject (the person who the data is about) The Data Protection Act The data subject has the right to: to inspect information held about them have incorrect information changed to apply for compensation if incorrect information has causes distress. Data Protection Act Information stored in a database must be accurate – what does this mean? A database could be created by a credit card company showing the credit rating of its customers Inaccurate information in this database could mean people being refused credit The Act states – information held on computer must be accurate and where necessary kept up to date Principals of the Data Protection Act Data held on computer must be: fairly and lawfully processed; processed for limited purposes; adequate, relevant and not excessive; accurate; not kept longer than necessary; processed in accordance with the data subject's rights; secure; not transferred to countries without adequate protection. The Computer Misuse Act This law makes it illegal to access a computer system without permission Unauthorised access Unauthorised access with intent to commit an offence Unauthorised modification of data Hacking and writing computer viruses are both made illegal by this act. The Copyright & Patents Act Most published material (including text, images, video, music, software etc) is protected by the Copyright, Design and Patents Act 1988. Copyright may be infringed if, without the prior permission of the copyright owner, you Copy a work (including scanning or storing electronically) Issue copies to the public Perform, show or play the work in public Broadcast the work or include it in a cable programme Make an adaptation of the work The Copyright & Patents Act If you do any of these without permission, you are liable to be held personally responsible. Infringing the law may be a criminal offence. Costs of Setting Up a Database System Initial costs Replacement costs Running costs Staff costs Staff training and retraining Expert Systems An expert system is a program that has access to a huge database of knowledge on one particular subject. The program can use this database to make decisions, draw conclusions and offer advice on the subject. This decisions/conclusions/advice are based on the facts contained within the database. The system is an EXPERT on the subject! More on Expert Systems The medical profession use Expert Systems to help diagnose patients Patients symptoms are entered into the computer The computer searches its database for all possible diseases or illnesses which match the symptoms The computer can then search its database for medication/treatment and advice Expert Systems Knowledge Base – Like a massive database but contains facts and rules Inference Engine or Expert System Shell – Compares new information with current data on the system Explanatory Interface (screen) – Displays questions to the user and displays how the system makes its conclusions/reasoning Artificial Intelligence AI stared in 1950’s with people programming computers to play chess A program is classed as AI if it can learn from its mistakes and perform better next time Verification of Data A data processing operator might key in hundreds of records a day How do we know she/he hasn’t make a tyiiing mistook! One way would be for data to be entered twice – perhaps by different operators This method of verification is called double entry Verification of Data Remember when you changed your password on the network you were asked to verify your new password by typing it in twice. The second time you type the password is used to verify what you typed this first time! Validation of Data To validate data means to check that is it allowable, sensible and within prescribed limits or range For example a day of the month must be in the range 1 – 31 If 33 were keyed in it would not be allowed and a message would be displayed telling the operator that it was an INVALID ENTRY In Conclusion A Database is a GPP Databases contain files, records and fields Databases can be searched and sorted by field or fields Databases are used in many businesses Databases can help make decisions Information stored in a database is subject to the Data Protection Act Key Fields A key field is used to identify a specific piece of information in a database A key field is something that is unique Date of birth could be the key field when searching a database of school pupils. Pupils may have the same name – John Smith – but are unlikely to have the same name and date of birth Your Candidate Number would be the key field in the SQA database