Databases

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

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 (e-mail or phone) Favourites Google iPod/MP3 player Web-sites, e.g. ECOS, YouTube, Amazon, etc. PVRs (Sky+, TiVO, etc.)

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.

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?

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!

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

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?

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

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!

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.

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

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

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

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

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