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Databases
Introduction
DEFINITION: A database is a collection of data or information which is

held together in an organised or logical way.


Computerised Databases
There are many examples of computerised databases, some of which
you will have used at home or school.
In order to find the right web sites…

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Type in the category you are looking for e.g. builder, type in the area e.g. Warwick and a
search will be performed on all the records in the database before giving you a list of results
which match your requirements a second or so later.
Details of every person in…

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Tables
Databases store data or information in tables, just like the one below:

The table allows you to see all of the records
stored in the database. Tables can store many
records, from a few dozen for a small database up
to millions for a large company database.



Records
As…

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Primary Key
When you started school, you were given a 'student ID' or a 'candidate number' (primary key).

This enables all of the girls called Charlotte Smith to be recognised.
Therefore, it is important that every single record in a database has something to uniquely
identify it and this is…

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Field Lengths
Once 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,…

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The main benefit of a relational database is
that data doesn't have to be duplicated. When
a customer books an appointment for their
pet, a new record is created on the
'appointment's table' and the relevant
Customer and Pet IDs are chosen.
Reducing data duplication reduces the amount
of data…

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Reports
Once you have run a query, the results are displayed in a table.
Whilst this shows all of the data, it isn't very nicely presented. Also, if you had hundreds of
results then it might be hard to look at all of the data and pick out specific things.…

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Comments

Miss Morgan

A brilliant revision guide, with all you need to know.

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