1. Databases

2. Database Introduction
In this lesson, we will be looking at:
What we mean by the word database
What we can do with a database
How information in a database is arranged
Why it is important that the information in a database is correct

3. Why Learn About Databases?
I think that databases are the most important thing in ICT!
As a user of ICT, you will use a database every day:
Contacts ( or phone)
Favourites
Google
iPod/MP3 player
Web-sites, e.g. ECOS, YouTube, Amazon, etc.
PVRs (Sky+, TiVO, etc.)

4. What is a Database? A database is a store of information.
The information is store in a very organised or structured way to make it easier to understand.
The information is usually stored in a particular order.
Examples include filing cabinets, card files, etc., as well as computer databases.

5. An Example? Think about a telephone directory:
Is it important that the data is structured (well organised)?
Does the order of the information make any difference?
Can we change the order?

6. Computer Databases A computer database can: Store information
Search through information for something specific
Sort information into different orders
Searching can be done much more quickly than with paper records, and you can’t keep changing the order of a filing cabinet!

7. Database Structure Databases are made up of:
fields – a fields is the smallest unit of storage, containing just one item of data
a field usually has a type – e.g. text, number, etc., so that the computer know what sort of information to expect
records – a record is all of the fields for one person or thing

8. Examples All sorts of organisations use databases:
What organisations would keep a database?
What information (i.e. records) would the database contain?
What data (i.e. fields) would be contained in those records?

9. Correct Information
Why is it important that the information in a database is correct?
if you search for something and it hasn’t been entered correctly, you won’t find it
if it was a doctor’s database, someone could end up getting the wrong treatment
there’s a saying in ICT – garbage in, garbage out – but the computer can’t really check whether information is right

10. Sources of Error
What could lead to incorrect information being retrieved from a database?
omission – missing things out altogether
transcription error – entering the information incorrectly
inconsistency – e.g. using F in some places and Female in others, so when you search for F you don’t find the females!

11. Answering Questions
You can use the sorting and searching facilities of databases to help you use your data to answer questions and perform research:
You can search to look for specific items of data
You can sort for the …st, e.g. highest, biggest, first, longest, last, etc.

12. Searching a Database
When you search you use criteria – this is the match that you are looking for, e.g. age is more than 10.
A search (or filter) with one criterion in a database is called a simple search
A search on two or more criteria at the same time is called a complex search
You can also use wildcards in your criteria for partial matches

13. AND & OR
When you combine two or more criteria you need to decide how to combine them – a bit like doing a sum in Maths
If you want to find records where all of your criteria are true, use AND
If you only want to match records from the database where any of the criteria are true, use OR

14. AND & OR People with blonde hair Blonde hair AND blue eyes
Blonde hair OR blue eyes
People with blue eyes

15. AND and OR AND and OR are called Boolean operators
When you mix them, AND is done before OR (like X is done before + in Maths) unless you use brackets
Sometimes AND and OR mean the opposite of the everyday use, so take care!
If you’re looking for an exact match (e.g. not more than or less than) it doesn’t make sense to use AND for two criteria using the same field

16. Partial Matches
Most database programs allow you to have criteria using partial matches such as contains, begins with, or ends with
If you can’t, you might see the * symbol used – this is called a wildcard
A wildcard can match one or more character of any type, e.g. the criteria owner is earl* would find villages owned by someone whose name began with earl