Download DATABASES

DATABASES
REVISION
BOOKLET (and exam questions)
NAME: ____________________________
CLASS: __________________
DATABASES
DEFINITION: A database is a collection of data or information which is held
together in an organised or logical way.
There are a few terms that you need to understand when learning about databases.
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
Each table contains a lot of records.
DEFINITION: A record is all of the data or information about one person or one
thing. In the table below, all of the information about each cartoon character is stored
in a 'row' or 'record'.
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.
Each of these individual pieces of information in a record is called a 'field'.
DEFINITION: a 'field' is one piece of data or information about a person or thing.
DATA TYPES
Here is a database table with the different data types set up for you to see:
PRIMARY KEY
Imagine what would happen if Mrs Smith telephoned the school to ask the secretary
to pass on a message to her daughter Charlotte.
If there were nothing to uniquely identify the students' records, the secretary would
have to search for all of the 'Charlotte Smiths' in school and then say, 'sorry to keep
you waiting Mrs Smith, could you just tell me if your daughter is in year 7, 8, 10, 11
or 13? And if she is in year 7, which one of these five girls is she?'
How about a patient going to have an operation. 'Oh hello Mr Jones, I have 4 Mr
Joneses having an operation today, can you tell me if yours is to remove your tonsils,
your arm, put your leg in a cast or give you a hair transplant?'. I think that would be
one very worried patient!
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'.
FLAT FILE DATABASE
When you first set up your database, you can choose to make a 'flat-file' database or a
With a flat file database, all of your data is stored in one large table.
RELATIONAL DATABASE
In the database below, the data is split up into sensible groups i.e. customer data, pets
data and appointments data. Then a separate table is made for each group.
Customer Table
Pet Table
Appointment Table
Once the tables have been set up, a relationship can be created to link them together as shown by the lines linking the tables below.
This is known as a 'relational database'.
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, because every time
you have to type the same data in, there is a risk you could mis-spell it.
Databases
1. Explain what the term ‘data’ means and give an example
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2. Explain what the term ‘information’ means and give an example
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3. Explain in your own words what a database is used for
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4. Give an example of a paper-based database
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5. Give an example of a computerised database
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6. Explain what each of these terms mean in relation to a database and give
an example:
Field
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Record
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File
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7. What is the purpose of a primary key?
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Which of the following database fields would be the most suitable to use as a
primary key (tick and explain why)?
Student Name
Student Address
Student Number
Student D.O.B.
Student’s Form
Which of the following database fields would be the most suitable to use as a
primary key (tick and explain why)?
Car model
Car make
Colour
Registration
number
Number of doors
8. Explain the difference between a ‘flat-file’ database and a ‘relational’
database
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9. When setting up your fields in a database, you should choose the most
appropriate datatypes. Explain what type of data would be stored in each of
the following datatypes
Alphanumeric (text)
Text and text with numbers
combined
Number
Numbers including those with
decimal places
Currency
Date/Time
Logical/ Boolean/ Yes No
Autonumber
Give an example for the following data types
Alphanumeric (text)
Number
Postcode – CV64 3RT
Currency
Date/Time
Logical/ Boolean/ Yes No
Autonumber
Which would be the most appropriate data type for the following?
£15.99
NQTR56N8J
15, Pear Tree Avenue
14th November 2002
Male Female
16
10. Explain why it is important to change the field length from the default of
50 characters to something more appropriate
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Decide which would be appropriate field lengths for the following fields
Gender (male/female)
Forename
House number and street name
Postcode
Telephone number
11. When setting up a database table, it is a good idea to use validation.
Explain what the purpose of validation is for.
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Validation cannot stop incorrect information from being entered into the
database. Explain why, giving an example
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There are different types of validation which you might choose to include. Fill
in the table on the next page:
Type of
Explanation
Example
validation
Required field
This means that data must be
entered into every field – the
field cannot be left blank
Type check
Range check
Presence check
Picture or
format check
Telephone number
12. Explain what the term ‘Garbage in Garbage out’ (GIGO) means
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13. Explain what the term ‘Verification’ means and give examples of how
verification can be performed
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14. Sometimes data which is used regularly is coded. Think of an appropriate
code to use for the following examples:
Males, Females
M F
Green, Red, Blue, Brown
Ford, Volkswagen, Honda, Toyota
Think of two advantages of coding data
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Think of a disadvantage of coding data
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15. Explain how you could search for data in a database and give an example
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In order to search for data from a database, you can use ‘operators’.
Complete the table below to show some of the operators which you can use.
Operator
Means
Example
>
Greater than
Greater than £5,000
Less than
Exactly £15
<>
Greater than or equal to
Less than or equal to
16. Once you have found the data you need from the query, you may want to
use it to create a report. Explain why this might be a good idea.
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DATABASES
Your school keeps details of their teachers in a database. They use codes for
some of the information.
A copy of their main table looks like the one below:
1
2
3
5
4
Jane Jones
F
F
BA
Simon Brown
Judith
Mathers
Lois Burns
Malcolm Field
David Chase
Margaret
Foster
Sally
Chadwick
Patrick
Roylick
Richard
Brand
M
F
HI
EN
F
F
BA
BA
F
M
M
F
GG
FR
SC
MA
P
F
P
P
BEd
PHD
MSc
BSc
F
ICT
F
BSc
M
DT
F
MA
M
RE
S
MA
PE
Some of the fields in this table might be a little hard to understand at first.
The school have shortened the answers and made them into a code.
What do you think the advantages of storing data as a code might be?
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The field headings should be:
Name
Gender
Subject
Qualification
Full/Part
time
Which subjects do you think these codes stand for :
Code
Subject
PE
HI
EN
GG
FR
SC
MA
ICT
DT
RE
The codes for qualifications are:
BSc = Batchelor of Science
Bed = Batchelor of Education
MSc = Master of Science
BA = Batchelor of Arts
PHD = Doctor of Philosophy
MA = Master of Arts
Write the teacher’s qualifications in full
Name
Jane Jones
Qualification
Simon Brown
Judith Mathers
Lois Burns
Malcolm Field
David Chase
Margaret Foster
Sally Chadwick
Patrick Roylick
Richard Brand
One piece of data is probably wrong in the database.
Which one do you think it is? ……………………………………………………………………
How many male teachers work at the school? ……………………………………………
How many female teachers work part time? ………………………………………………
Which teacher has an MSc and is male? ……………………………………………………
Which teachers are female and have a BA? ……………………………………………….
The following teachers will be joining in September. Add their details to the
database:


Mrs Gillian White who teachers science, works full time and has a
Master of Science degree
Mr Julian Waite who works part time teaching history and has a
Batchelor of Arts degree
Name
Gender
Subject
Qualification
Full/Part
time
DATABASES 2
The local zoo has created a database to store records about each of the
animals.
A copy of their main table looks like the one below:
Animal
Name
Gender
Age
Food
Breed
Giant Panda
Pongo
Giant Panda
Penguin
Lion
Lion
Crocodile
Gorilla
Zebra
Snake
Parrot
Bongo
Pingu
Hermes
Tarsa
Spike
Gemella
Stripey
Leyla
Robina
8
M
F
M
M
F
M
F
M
F
F
7
5
4
4
7
122
8
2
25
Bamboo
Bamboo
Fish
Fresh meat
Fresh meat
Fresh meat
Fruit
Grass
Live mice
Nuts and
seeds
1. How many fields are there in the zoo database? ……………………………………
2. How many records are stored in the database? ………………………………………
3. One of the fields has been sorted into ascending order.
Which field is it? ………………………………………………………………………………………
4. One item of data in the database looks incorrect.
Which one do you think it is?…………………………………………………………………….
5. Explain your answer
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6. A code has been used for the ‘gender’ field.
What do you think the code stands for? …………………………………………………….
7. Why might a code be used?
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8. How many animals are there in the database which are female?………………
9. Give the names of the animals which eat fresh bamboo?
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10. Give the name of the animal which eats fresh meat and is female?…………