Mark Dixon 1 21 – Databases: Multiple Tables. Mark Dixon 2 Questions: Databases How many records are in the following table? How many fields does the.
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Mark Dixon 1
21 – Databases: Multiple Tables
Mark Dixon 2
Questions: Databases• How many records are in the following table?• How many fields does the following table have?
64
CountryName Population Land Mass Continent
UK 60776238 241590 EuropeSpain 40448191 499542 EuropeGermany 82400996 349223 EuropeEgypt 80335036 995450 AfricaKenya 36913721 569250 AfricaChina 1321851888 9326410 Asia
Mark Dixon 3
Questions: SQL• Write an SQL statement to display the name and
land mass of all countries in Africa.
SELECT Name, Land MassFROM Country WHERE Continent = 'Africa';
CountryName Population Land Mass Continent
UK 60776238 241590 EuropeSpain 40448191 499542 EuropeGermany 82400996 349223 EuropeEgypt 80335036 995450 AfricaKenya 36913721 569250 AfricaChina 1321851888 9326410 Asia
Mark Dixon 4
Session Aims & Objectives• Aims
– To add dealing with multiple tables to your understanding of databases
• Objectives,by end of this week’s sessions, you should be able to:
– identify a suitable primary key for a table– identify duplicated data in a single table– split that table to reduce data redundancy,
using a suitable foreign key– generate SQL statements to (temporarily)
join tables, and use these in your code
Mark Dixon 5
Data Duplication• Look for repeating data:
Track Title Artist Name Country
Paranoid Black Sabbath UK
Falling in Love Aerosmith US
Pink Aerosmith US
Love in an Elevator Aerosmith US
Smooth Criminal Alien Ant Farm US
Meaning of Life Disturbed US
The Game Disturbed US
Voices Disturbed US
Down with the Sickness Disturbed US
Track
Mark Dixon 6
Problem: Data Duplication• takes up lots of space
• can become inconsistent (misspellings)
• difficult to change (need to change each instance)
• difficult to search (misspellings)
Mark Dixon 7
Solution: Normalisation• Part of database design
• Process of breaking data down (splitting)
• Codd– 7 stages of normalisation
• Mathematical• Difficult to apply stages• Most professionals do it instinctively
Mark Dixon 8
Relations (tables)
Track Title
Paranoid
Falling in Love Aerosmith US
Pink Aerosmith US
Love in an Elevator Aerosmith US
Smooth Criminal Alien Ant Farm US
Meaning of Life Disturbed US
The Game Disturbed US
Voices Disturbed US
Down with the Sickness Disturbed US
Track
Artist Name Country
Black Sabbath UK
Mark Dixon 9
Relations (tables)
Track Title
Paranoid
Falling in Love Aerosmith US
Pink Aerosmith US
Love in an Elevator Aerosmith US
Smooth Criminal Alien Ant Farm US
Meaning of Life Disturbed US
The Game Disturbed US
Voices Disturbed US
Down with the Sickness Disturbed US
Track
Artist ID
1
Artist
Artist Name Country
Black Sabbath UK
ID Artist Name Country
1 Black Sabbath UK
Mark Dixon 10
Relations (tables)
Track Title
Paranoid
Falling in Love
Pink Aerosmith US
Love in an Elevator Aerosmith US
Smooth Criminal Alien Ant Farm US
Meaning of Life Disturbed US
The Game Disturbed US
Voices Disturbed US
Down with the Sickness Disturbed US
Track
Artist ID
1
Artist
ID Artist Name Country
1 Black Sabbath UKAerosmith US
ID Artist Name Country
1 Black Sabbath UK
2 Aerosmith US2
Mark Dixon 11
Relations (tables)
Track Title
Paranoid
Falling in Love
Pink
Love in an Elevator Aerosmith US
Smooth Criminal Alien Ant Farm US
Meaning of Life Disturbed US
The Game Disturbed US
Voices Disturbed US
Down with the Sickness Disturbed US
Track
Artist ID
1
2
2
Artist
ID Artist Name Country
1 Black Sabbath UK
2 Aerosmith US
Mark Dixon 12
Relations (tables)
Track Title
Paranoid
Falling in Love
Pink
Love in an Elevator
Smooth Criminal Alien Ant Farm US
Meaning of Life Disturbed US
The Game Disturbed US
Voices Disturbed US
Down with the Sickness Disturbed US
Track
Artist ID
1
2
2
2
Artist
ID Artist Name Country
1 Black Sabbath UK
2 Aerosmith US
Mark Dixon 13
Relations (tables)
Track Title
Paranoid
Falling in Love
Pink
Love in an Elevator
Smooth Criminal
Meaning of Life Disturbed US
The Game Disturbed US
Voices Disturbed US
Down with the Sickness Disturbed US
Track
Artist ID
1
2
2
2
3
Artist
ID Artist Name Country
1 Black Sabbath UK
2 Aerosmith US
3 Alien Ant Farm US
Mark Dixon 14
Relations (tables)
Track Title
Paranoid
Falling in Love
Pink
Love in an Elevator
Smooth Criminal
Meaning of Life
The Game Disturbed US
Voices Disturbed US
Down with the Sickness Disturbed US
Track
Artist ID
1
2
2
2
3
4
Artist
ID Artist Name Country
1 Black Sabbath UK
2 Aerosmith US
3 Alien Ant Farm US
4 Disturbed US
Mark Dixon 15
Relations (tables)
Track Title
Paranoid
Falling in Love
Pink
Love in an Elevator
Smooth Criminal
Meaning of Life
The Game
Voices Disturbed US
Down with the Sickness Disturbed US
Track
Artist ID
1
2
2
2
3
4
4
Artist
ID Artist Name Country
1 Black Sabbath UK
2 Aerosmith US
3 Alien Ant Farm US
4 Disturbed US
Mark Dixon 16
Relations (tables)
Track Title
Paranoid
Falling in Love
Pink
Love in an Elevator
Smooth Criminal
Meaning of Life
The Game
Voices
Down with the Sickness Disturbed US
Track
Artist ID
1
2
2
2
3
4
4
4
Artist
ID Artist Name Country
1 Black Sabbath UK
2 Aerosmith US
3 Alien Ant Farm US
4 Disturbed US
Mark Dixon 17
Relations (tables)
Track Title Artist ID
Paranoid 1
Falling in Love 2
Pink 2
Love in an Elevator 2
Smooth Criminal 3
Meaning of Life 4
The Game 4
Voices 4
Down with the Sickness 4
Track Artist
ID Artist Name Country
1 Black Sabbath UK
2 Aerosmith US
3 Alien Ant Farm US
4 Disturbed US
PrimaryKey
ForeignKey
Mark Dixon 18
Question: Prescriptions• Identify duplication and separate:
Date Surname Forenames Drug Name
6 Jan 04 Jones Alison Co-codamol
11 Jan 04 Smith Bob Tegretol
18 Jan 04 Hope John Co-codamol
5 Feb 04 Johnson Sally Co-codamol
8 Feb 04 Smith Bob Tegretol
10 Feb 04 Smith Bob Sorbitol
Prescription
Mark Dixon 19
Question: Solution
Date PatientID DrugID
6 Jan 04 1 1
11 Jan 04 2 2
18 Jan 04 3 1
5 Feb 04 4 1
8 Feb 04 2 2
10 Feb 04 2 3
Prescription
PatientID Surname Forenames
1 Jones Alison
2 Smith Bob
3 Hope John
4 Johnson Sally
Patient
DrugID Drug Name
1 Co-codamol
2 Tegretol
3 Sorbitol
Drug
Mark Dixon 20
People Database (with Hobbies)ID Surname Forenames Phone email
1 Dixon Mark 01752 232556 mark.dixon@plymouth.ac.uk
2 Smith John 01752 111111 john.smith@john.smith.ac.uk
3 Jones Sally 01752 888888 sally.jones@sally.jones.com
4 Bloggs Fred 01752 123123 fred.bloggs@aaaaaa.com
5 Anderson Genny 01752 987987 genny@bbbb.cccc.com
HobbyID Description PersonID
1 Archery 1
2 Herpetology 1
3 Music 1
4 Football 2
5 Rugby 2
6 Hitting people with swords 1
Hobby
Person
Mark Dixon 21
Entity-relationship diagrams• Each table in db
– stores details of entity• shown as rectangular box
•Relationships between tables
–represent relationships between entities
•shown as line between entities (boxes)
Person Hobby
Mark Dixon 22
Relationship Types• One-to-one
• One-to-many
• Many-to-one
• Many-to-many– (can't be implemented in relational database)
A B
A B
A B
A B
Mark Dixon 23
Question: Which relationship type?
ID Surname Forenames Phone email
1 Dixon Mark 01752 232556 mark.dixon@plymouth.ac.uk
2 Smith John 01752 111111 john.smith@john.smith.ac.uk
3 Jones Sally 01752 888888 sally.jones@sally.jones.com
4 Bloggs Fred 01752 123123 fred.bloggs@aaaaaa.com
5 Anderson Genny 01752 987987 genny@bbbb.cccc.com
HobbyID Description PersonID
1 Archery 1
2 Herpetology 1
3 Music 1
4 Football 2
5 Rugby 2
6 Hitting people with swords 1
Hobby
Person
Person
Hobby
Mark Dixon 24
SQL: Joining tables
SELECT * FROM Person, Hobby;
Two tables
Cartesian set(all recordcombinations):
ID Surname Forenames Phone email HobbyID Description PersonID1 Dixon Mark 01752 232556 mark.dixon@plymouth.ac.uk 7 Archery 12 Smith John 01752 111111 john.smith@john.smith.ac.uk 7 Archery 13 Jones Sally 01752 888888 sally.jones@sally.jones.com 7 Archery 14 Bloggs Fred 01752 123123 fred.bloggs@aaaaaa.com 7 Archery 15 Anderson Genny 01752 987987 genny@bbbb.cccc.com 7 Archery 11 Dixon Mark 01752 232556 mark.dixon@plymouth.ac.uk 8 Herpetology 12 Smith John 01752 111111 john.smith@john.smith.ac.uk 8 Herpetology 13 Jones Sally 01752 888888 sally.jones@sally.jones.com 8 Herpetology 14 Bloggs Fred 01752 123123 fred.bloggs@aaaaaa.com 8 Herpetology 15 Anderson Genny 01752 987987 genny@bbbb.cccc.com 8 Herpetology 11 Dixon Mark 01752 232556 mark.dixon@plymouth.ac.uk 9 Music 12 Smith John 01752 111111 john.smith@john.smith.ac.uk 9 Music 13 Jones Sally 01752 888888 sally.jones@sally.jones.com 9 Music 14 Bloggs Fred 01752 123123 fred.bloggs@aaaaaa.com 9 Music 15 Anderson Genny 01752 987987 genny@bbbb.cccc.com 9 Music 11 Dixon Mark 01752 232556 mark.dixon@plymouth.ac.uk 10 Football 22 Smith John 01752 111111 john.smith@john.smith.ac.uk 10 Football 23 Jones Sally 01752 888888 sally.jones@sally.jones.com 10 Football 24 Bloggs Fred 01752 123123 fred.bloggs@aaaaaa.com 10 Football 25 Anderson Genny 01752 987987 genny@bbbb.cccc.com 10 Football 21 Dixon Mark 01752 232556 mark.dixon@plymouth.ac.uk 11 Rugby 22 Smith John 01752 111111 john.smith@john.smith.ac.uk 11 Rugby 23 Jones Sally 01752 888888 sally.jones@sally.jones.com 11 Rugby 24 Bloggs Fred 01752 123123 fred.bloggs@aaaaaa.com 11 Rugby 25 Anderson Genny 01752 987987 genny@bbbb.cccc.com 11 Rugby 21 Dixon Mark 01752 232556 mark.dixon@plymouth.ac.uk 12 Hitting people with swords 12 Smith John 01752 111111 john.smith@john.smith.ac.uk 12 Hitting people with swords 13 Jones Sally 01752 888888 sally.jones@sally.jones.com 12 Hitting people with swords 14 Bloggs Fred 01752 123123 fred.bloggs@aaaaaa.com 12 Hitting people with swords 15 Anderson Genny 01752 987987 genny@bbbb.cccc.com 12 Hitting people with swords 1
Mark Dixon 25
SQL: Joining tables
SELECT *FROM Person, HobbyWHERE Person.ID = Hobby.PersonID;
Two tables
Matching recordsID Surname Forenames Phone email HobbyID Description PersonID
1 Dixon Mark 01752 232556 mark.dixon@plymouth.ac.uk 1 Archery 1
1 Dixon Mark 01752 232556 mark.dixon@plymouth.ac.uk 2 Herpetology 1
1 Dixon Mark 01752 232556 mark.dixon@plymouth.ac.uk 3 Music 1
1 Dixon Mark 01752 232556 mark.dixon@plymouth.ac.uk 6 Hitting people with swords 1
2 Smith John 01752 111111 john.smith@john.smith.ac.uk 4 Football 2
2 Smith John 01752 111111 john.smith@john.smith.ac.uk 5 Rugby 2
Mark Dixon 26
SQL: Joining tables
ID Surname
1 Dixon
1 Dixon
1 Dixon
1 Dixon
2 Smith
2 Smith
SELECT ID, SurnameFROM Person, HobbyWHERE Person.ID = Hobby.PersonID;
Mark Dixon 27
Question: SQL Joining Tables• Write an SQL query to join the following:
Track Title Artist ID
Paranoid 1
Falling in Love 2
Pink 2
Love in an Elevator 2
Smooth Criminal 3
Meaning of Life 4
The Game 4
Voices 4
Down with the Sickness 4
Track Artist
ID Artist Name Country
1 Black Sabbath UK
2 Aerosmith US
3 Alien Ant Farm US
4 Disturbed US
Mark Dixon 28
MS Access: SQL Query• Open database• Create new query• Select SQL item from drop-down list
SQL View DataSheet View
Mark Dixon 29
SQL: More• Loads more:
– group by– aggregate functions: average, count– inner joins– outer joins (left and right)
• Have a look at:– http://www.w3schools.com/sql/sql_join.asp
Mark Dixon 30
Tutorial Exercise: Countries• LEARNING OBJECTIVE:
avoid duplicate data by splitting a tablecreate a web-page to temporarily re-join and display the data
• Task 1: Create the Countries database (from the lecture) with the Country table.
• Task 2: Split the Country table to remove duplicate data.identify the duplicate dataput it in a separate tablecreate a primary key for the new tablecreate a foreign key in the old table that links to the new table
• Task 3: Create a web page to display a list of Countries with associated data (Population, Land Mass, and Continent).
• Task 4: Add a text box and button to your page. When the user clicks the button the page should display only countries that match the continent entered in the text box (e.g. if the user types in Africa and clicks the button, only the African countries should be displayed).
Mark Dixon 31
Tutorial Exercise: Music• Task 1: Create the Music database (from the lecture) with the Track
and Artist tables.• Task 2: Create a web page to display a list of Artists.• Task 4: Change that web page, so that each artist name is a link to
another page, which displays all the tracks by that artist. Hint: Use query strings to pass the artist ID between pages.
Mark Dixon 32
Tutorial Exercise: Prescriptions• Task 1: Create the Prescription database (from the lecture) with the
Prescription, Patient, and Drug tables.• Task 2: Create a web page to display a list of Drugs.• Task 3: Change that web page, so that each drug name is a link to
another page, which displays all the people using that drug.
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