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  • Created by: Hannah
  • Created on: 31-05-11 13:12
Preview of databases

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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 for you. Search engines need a vast
computerised database which they search using your entered keywords
Many schools now use electronic registers. These contain a database
with records for every student in the school.
The database records student's attendance both at school and in
If you don't want to use the paperbased version, a telephone number can be found using an
online database such as

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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 the United Kingdom over the age of 18 are kept on local electoral
registers. This database records your name, address, date of birth and national insurance
number.…read more

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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.
As you saw previously, each table
store a great deal of data.
table contains a lot of records.
DEFINITION: A record is all of
the data or information about one
person or one thing.…read more

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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 called the 'Primary Key' or sometimes the 'Key Field'.…read more

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Field Lengths
Once you have chosen your datatypes, you need to think about the best 'field length' for each
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.
In some situations, you may need to use all 50, but think about forenames. How long is the
longest one you can think of? Probably around 12.…read more

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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 which needs to be stored, thus making
the database smaller. It also reduces the risk
of mistakes.
Database Queries
Databases are extremely good at
storing data or information.…read more

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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. There is a
much nicer way of presenting the same data, this is called a report:
This report looks much more
professional than a table of data.…read more

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Miss Morgan

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

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