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The information On Databases

Edward Coburn

on 6 November 2009

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Transcript of Databases

Databases Introduction DEFINITION: A database is a collection of data or information which is held together in an organised or logical way. Have you ever used the yellow pages? Have you ever kept details of your friends or families birthdays in a birthday book? If you answered yes to any of these questions, then you have used a 'Paper based' database! computerised Databases There are many examples of computerised databases, some of which you will have used at home or school. Many schools now use electronic registers, These contain a database with records for every student in the school. An example of a computerised database would be a search engine, they are basically databases used on a computer or electronic device Computerised vs paper based databases Can hold a vast amount of data very fast to find specific data limited by physical storage space Can take a while to manually search through data
Can be kept secure with passwords Has to be locked up manually Tables Databases store information in tables, These help keep the information organised and easy to find Example Records As you saw previously, each table can store a whole lot of data DEFINITION: A record is all of the data or information about one person or one thing. Fields Each table contains a lot of records.

A record is made up of lots of individual pieces of information. Look at Wonder Woman's record: it stores her first name, last name, address, city and age.
DEFINITION: a 'field' is one piece of data or information about a person or thing. Data Types When you set up a database, you need to think about the
'data type' which you will use for each field
Here is a database table with the different data types set up for you to see primary Key It is important that every single record in a database
has something to uniquely identify it and this is called
the 'Primary Key' or sometimes the 'Key Field' When you started school, you were given a 'student ID' or an 'office number'
This enables all of the girls called _________ to be recognised. Field Lengths When you have chosen your datatypes, you need to
think about the best 'field length' for each field. Most databases will have a default
field length set up, in this case it is 50 This means that each text field is able to store up to 50 letters, numbers or symbols. Validation As well as choosing the correct data types to try to reduce the number of errors made when entering data into the database, there is another method that can be used when setting up the table. This is called 'Validation'. What Validation can do, is to check that the
data is sensible, reasonable and allowable Verification Verification means to check the data that you have entered against the original source data Think about when you choose a new password, you have to type it in twice. This lets the computer check if you have typed it exactly the same both times and not made a mistake Flat File Databases When you first set up your database, you can
choose to make a 'flat-file' database or a
'relational database'
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