ICT - databases

ICT - databases

1. Types of data

   • Number
     • Real
       • Any number including whole numbers and fractions
     • Interger
       • A whole number
   • Text/string
     • Letters, numbers and other characters such as puntuation
   • Date/time
     • Any time or date
   • Currency
     • Money including foreign currency

2. Defintions

   • Database - an organised collection of related data. It is possible to edit, add, manage and retrieve data. The structure of a database allows data to be found and used quickly
     • A field is a single item of data within a record. E.g. the surname of a person
     • A record consists of a collection of related fields.
     • A file is a collection of related fields
     • A key field uniquely identities each record. No two records have the same data in their key field.
       • The purpose of the key field is to be able to refer to an individual record using a single field.
     • Uses of a database
       • Add, change or delete records
       • Search for a particular record
       • Sort the record in a given order
       • Print reports about some aspect of the database
   • A report is a printed document that contains data from a database, organised and analysed in a certain way.
   • Forms are used to make data more attractive and secure rather than entering data into raw tables
   • A calculated field is used if the data changes from day to day, for example age
   • One main use of databases is to fid information quickly. To search for information you use a query. You are "querying a database". A query specifies for and what records you are searching for and what fields from the records you would like to display
     • Simple search query - looks for data in one field
     • Complex query search - looks at data with multiple criteria
     • You use wildcard searches in a query for data that only you know part of. for example find all the surnames beginning with the letter S

3. Types of validation

   • Range check
     • The data entered must be in a sensible range
   • Type check
     • This ensures that the data is of the correct type
   • Length check
     • The length of the input is checked for the number of characters used.
   • Presence check
     • Some data has to be entered
   • Format/ Picture check
     • If the data entered has a particular pattern then an input mask can be used to force the data to conform
   • Lookup lists
     • If the data entered consists of a limited number of possible entries then the computure can compare entry with a list of allowed answes

4. Security

   • If data is secure
     • It can't fall into the hands of unauthorised people
     • It can't be deystroyed
     • It can't be altered
   • Software methods
     • Passwords
       • Authorised users are given a username, each user also has a password
     • Access rights can be placed in individual files to give:
       • No right to access the file
       • Read access (user can view file but not alter it)
       • Write access (allowing the user to alter the contents of the file)
     • Back-ups
       • Back-ups are saved onto removable media (e.g. CDs, DVDs, memory sticks), stored at a separate location in a locked room or fireproof safe, made regularly.
       • A back-up is a second copy of the data

5. Benefits of using a database

   • Fast access
     • Faster to find data than with a filling cabinet
   • Easy to edit
     • You can easily change and update data
   • Validation
     • You can set checks on the data entered to check that it is appropriate
   • Reports
     • Results of searches can be used can be used to print reports that may help management in their decision marking
   • Sharing
     • Databases can be shared with any number of users, any user can edit the data
   • Security
     • You can set passwords on database