1. Database revision for higher

2. Field Types
Text – Mixture of letters, words, numbers and/or symbols. Can’t perform a calculation on a number in a text field.
Number
Integer – whole numbers.
Real – decimal/floating point numbers.
Date
Time

3. Field Types - continued
Graphic
Calculated – field containing a formula.
Link - a hyperlink to a file outside the database. The file could be a web page or a document.
Boolean - holds one of two values. E.g. Yes/No
Object – field that contains a variety of different types of data such as a presentation, audio, video or graphic

4. Calculated field
Uses the values in another field or fields to calculate the contents of a new field.

5. Validation
Validation is used to make sure that a user only inputs data in the correct format. If the user makes an error the database will display an error message and ask the user to re-enter.

6. Validation 4 different types of validation: Presence Check
Restricted Choice
Field Length
Range Check

7. Presence check
When a presence check is set up on a field, that field cannot be left blank, some data must be entered into it.
The presence check does not check that the data is correct, only that some data is present.
You may have used this before when completing an online form. If you try to leave a field blank you will be asked to go back and enter information into the field.

8. Restricted Choice
When a restricted choice check is added to a field it gives the user a list of options that they can select.
Saves time & reduces the amount of errors entered.
Can you give some other examples of restricted choice checks you have used when entering a form on the internet?

9. Field length A Database designer will restrict the field length to:
Save the amount of memory a database file takes up.
Stop someone from entering too many characters into a field.
E.g. If a user inputs a telephone number of an error should appear!

10. Range check
The range of a field refers to the acceptable range of values it will accept.
E.g. if a field holds the month as a number from 1 (January) to 12 (December) then the range is 1 to 12
>=1 and <=12
If a number outside the range is typed in an error message will appear.

11. Types of Database
The two main types of computerised databases are flat-file and relational.
Flat-File – a flat file database is stored in a single table:

12. Flat file database problems
Data is duplicated – when a new record is created the member details and game details would have to be entered
Data duplication wastes space on backing storage
Data duplication increases the chance of human error when typing in the same customer’s details or game details a number of times or when changing data
A customer’s details can only be recorded when they rent something
Removing a game from the database may remove the only record that stores details of a member. The member details will be lost!

13. Flat file database problems
Insertion Problems – adding a record - it is not possible to store details of a game without a member taking it out.
Deletion Problems – deleting a record - if a game is deleted it may delete the only occurrence of a member.
Update Problems – changing a record - if a member changes their name or address more than one record would need to be updated.

14. Library Flat File Database System ExampleID
surname
forename
address
town
post code
book
ISBN
date
borrowed
returned
001
Bell
John
23 High Street
Arbroath
DD7 5FT
Fiction in Action
12/4/13
19/4/13
Fishing
013
Smith
Emma
17 Main Street
Carnoustie
DD7 5VF
Mother’s Curse
20/4/13
067
Roberts
Susan
The Elms
DD7 8HG
My Life
18/4/13
24/4/13
There are a number of problems associated with storing the data in this form as a single table.
Can you spot the:
Insertion Problem
Deletion Problem
Update Problems

15. solving flat file database problems
Create a Relational database i.e. linked table database
stores data in more than one table
stores data once
remove the possibility of data duplication and data inconsistency

16. Linked Tables/Relational Database
The previous table contains multi-valued fields. The fields subject, ISBN, date borrowed and date returned contain more than one value for the member John Bell. ID
surname
forename
address
town
post code
book
ISBN
date
borrowed
returned
001
Bell
John
23 High Street
Arbroath
DD7 5FT
Fiction in Action
12/4/13
19/4/13
Fishing
013
Smith
Emma
17 Main Street
Carnoustie
DD7 5VF
Mother’s Curse
20/4/13
067
Roberts
Susan
The Elms
DD7 8HG
My Life
18/4/13
24/4/13

17. Linked Tables/relational database
Remove the repeating values and place them in a table of their own
Library database:-
MEMBER (MemberID, Surname, Forename, Address, Town, Postcode)
LOAN (ISBN, Book, DateBorrowed, DateReturned, *MemberID)
MemberID is the primary key in the MEMBER table.
ISBN & Member ID are the primary key in the LOAN table. MemberID is a foreign key in the LOAN table

18. Primary Key A field or set of fields that uniquely identify a record
E.g. In a customer table, there may be a number of clients called John Smith so to uniquely identify which John Smith there could be a key field called Customer ID
Primary keys are underlined
What primary key would be used to identify you in the following databases:
School
SQA
Doctors Surgery
Dentist

19. Foreign Key A field that links two tables together
It is not a primary key in its own table, but is a primary key in another table
Library example –
Member ID is the primary key in the customer table and the foreign key in the loan table
MEMBER(MemberID, Surname, Forename, Address, Town, Postcode)
LOAN(ISBN, Book, DateBorrowed, DateReturned, *MemberID)
Foreign keys are indicated by a star *

20. Hardware Database Example
Can you spot the multi-valued fields?
Can you spot data duplication?
Now try to turn this into a linked table and solve the problems above.

21. Hardware Database Example
Solve flat-file database problemswe split the table into 2 tables by removing the repeating values into a table of their own and creating primary keys.
Now there is no connection between orders and customers. What should we do to fix this?

22. Structures and links (Database)
Higher Computing Science

23. What you need to know and do
Implementation of relational databases with a minimum of three linked data tables
Description, implementation and exemplification of compound keys and surrogate keys
Description, exemplification and identification of entity relationships (one-to-one, one-to-many, many-to-many)
Description, exemplification and implementation of entity relationship diagrams
Description and implementation of complex database operations including:
input (forms)
searching/sorting/calculations (queries)
output (reports)

24. Implementation of relational databases with a minimum of three linked data tables
Data modelling is used to decide which tables and fields are required
There follows examples of 3 databases so that you understand why the tables exist and why contain those fields
You do not need to be able to carry out the process of normalisation

25. Example of normalisation
Bits ‘N’ PCs
Example of normalisation

26. Bits ‘n’ PCs Limited Bits ‘n’ PCs Limited
Order number: Order Date: 01/02/2004
Customer Number:
Name: Mrs Joanna Bloggs
Address: 12 High Street
Auchenshoogle
Inverness-shire
Postcode: IV99 2QW Telephone No:
Total: £19.69
Item Code
Description
Unit Cost
Quantity
Sub-Total
1170
Medium widgets (blue)
£2.25 3
£6.75
5499
Large deluxe widget (red)
£9.99 1
7937
Small economy widget (green)
£0.59 5
£2.95

27. Un-normalised form Write down all the attributes that must be stored
Identify a primary key

28. Large deluxe widget (red) Small economy widget (green)
Bits ‘n’ PCs Limited
Bits ‘n’ PCs Limited
Order number: Order Date: 01/02/2004
Customer Number: 34567
Customer Name: Mrs Joanna Bloggs
Address: 12 High Street
Auchenshoogle
Inverness-shire
Postcode: IV99 2QW Telephone No:
Total: £19.69
Order(
Order_number
Order_date
Customer_number
Customer_name
Address
Postcode
Telephone_no
Item_code
Description
Unit_cost
Quantity)
Item Code
Description
Unit Cost
Quantity
Sub-Total
1170
Medium widgets (blue)
£2.25 3
£6.75
5499
Large deluxe widget (red)
£9.99 1
7937
Small economy widget (green)
£0.59 5
£2.95

29. Sample data Multi-valued attributes = repeating data items Oder_number
Order_date
Customer_number
Customer_name
Address
Postcode
Telephone number
Item Code
Description
Unit Cost
Quantity
654321
1/9/04
234567
Mrs Joanna Bloggs
12 High Street
Aunchenshoogle
Inverness-shire
IV99 2QW
1170
Medium widgets (blue)
£2.25 3
5499
Large deluxe widget (red)
£9.99 1
7937
Small economy widget (green)
£0.59 5
Multi-valued attributes = repeating data items

30. Un-normalised Form with repeating data items identified
Order ( Order_number
Order_date
Customer_number
Customer_name
Address
Postcode
Telephone_no
Item_code
Description
Unit_cost
Quantity)

31. First Normal form
Remove all multi-valued attributes to a new entity

32. Customer UNF 1NF 2NF 3NF Order ( Order_number Order_date
Customer_number
Customer_name
Address
Postcode
Telephone_no
Item_code
Description
Unit_cost
Quantity)
Order
( Order_number
Order_date
Customer-_number
Customer_name
Address
Postcode
Telephone_no)
Order
( Order_number
Order_date
*Customer-_number)
Customer_name
Address
Postcode
Telephone_no)
Customer
(Customer_number
Item_code
Description
Unit_cost
Quantity)
Order_item
( *Order_number
*Item_code
Quantity)
Order_item
( *Order_number
Order_item
( *Order_number
*Item_code
Quantity)
Description
Unit_cost
item
(Item_code
item
(Item_code
Description
Unit_cost

33. Description, implementation and exemplification of compound keys and surrogate keys
a primary key that consists of more than one field
uniquely identifies a record
used when there is no primary key – i.e. no single attribute (field) that stores a unique value for each entity occurrence (record)
E.g. Oder_number and Item_code in the Order_item table
Surrogate key:-
a primary key that is created to uniquely identify a record when there is no primary key or when a compound key is not attractive e.g. has 3 fields
E.g. Item_code, Customer_number

34. Description, exemplification and identification of entity relationships (one-to-one, one-to-many, many-to-many)
In your Genius Guide:-
One-to-one - a primary key links one record in one table to one record in another table, where it is a foreign key
One-to-many - a primary key links one record to more than one record in another table, where it is a foreign key
Many-to-many– when read in both directions – read one-to-many from left to right and one-to-many from right to left
The full story follows .....

35. E/R occurrence modelling
Systems analyst uses E/R occurrence modelling to identify relationship between two entities
To create an E/R occurrence diagram the systems analyst must fully understand the system and have sample data

36. Drawing an E/R occurrence diagram
1. Create a list of primary key values
Van Reg
P385 ASA
KY51 AFZ
YT71 7YE
D842 YSA
Client Nbr
2711
0921
2. Link primary keys

37. What is the point of an E/R occurrence diagram?
Pattern of lines identifies nature of relationship between the two entity sets
3 possible patterns. One pattern for each relationship cardinality:-
1 to 1
1 to many
Many to many

38. 1 to 1 relationship Create a list of primary key values
Link key values
Computer name
Paris
Washington
London
Geneva
Edinburgh
Payroll number
030/829112
040/881929
040/546781
030/112000
050/444878

39. 1 to Many Relationship Course code CC871 CC101 CC891 Student ID
NW872818C
RT77712C
UI828211E
NQ829111D
NW872819C

40. Many to Many Relationship
Food supplier
Beefy soup Co.
Baters Ltd
Luxury Soup
McCampbells
Outlet
Big store
ADSA Market
SafeCo

41. Description, exemplification and implementation of entity relationship diagrams
Created by a systems analyst to illustrate the entities (tables) and the relationships that exist between them that were identified when designing the database
Picture of entities, relationships, (attributes/fields) and cardinality
Example:-  

42. Entity Relationship Diagram
Order
( Order_number
Order_date
*Customer-_number)
Customer
(Customer_number
Customer_name
Address
Postcode
Telephone_no)
Order_item
( *Order_number
*Item_code
Quantity)
item
(Item_code
Description
Unit_cost)
Entity Relationship Diagram
Order
Customer
Order_item
Item

43. Example of normalisation and ER diagram
Application Forms
Example of normalisation and ER diagram

44. Application form Application no: 56 Applicant no: 118 Applicant name:
Johnathon Appleby
Date of birth:
3/2/1990
Applicant Address:
3 Sycamore Street
Valleyfield
Aberdeen
AB65 WY65
Course code:
GD65
Course title:
Information Systems
Date received:
7/11/2006
Qualification code
Qualification Title
Grade Obtained
DT567
S Grade Maths 1
KU786
S Grade English
FE453
S Grade Computing
MK897
S Grade History
DS432
S Grade French 2
ML987
S Grade Art & Design
DP874
S Grade Chemistry
CD432
S Grade Physics

45. Entities and attributes
Application
Applicant
Course
Qualification
Qual_code
Application_no
*Applicant_no
*Course_code
Date_received
Applicant_no
Applicant _name
Applicant_address
Date_of_birth
Course_code
Course_title
*Application_no
*Qualification code
Grade_obtained
Qualification code
Qualification_title
Identify a surrogate key and a compound key
Draw an ER diagram

46. Draw the ER Diagram for Application forms
Application (Application_no
*Applicant_no
*Course_code
Date_received)
Applicant (Applicant_no
Applicant_name
Applicant_address
Date_of_birth)
Course (Course_code
Course_title)
Qualification (*Application_no
*Qualification code
Grade_obtained)
Qual_code (Qualification code
Qualification_title)
Applicant
Course
Application
Qualification
Qual_code

47. ER diagrams For you to do
Room service
Films
Sports Day
Zoo
ICT Courses

48. Exemplification and implementation of data dictionary including name, type, size, required and validation
 Created when designing a database
Shows the structure of tables and the properties of fields
A table that lists the attributes(fields) of each entity (table) with their properties:-
Name
Type
Size
Required
Validation

49. Basic rules used when naming attributes (fields) and entity sets (tables)
The names must be suitable for most database packages:-
Use lower case letter
No spaces – use underscore _
Meaningful names
Keep it short e.g customer_tel_nbr

50. Data dictionary columns
Entity set – becomes the name of the table when it’s created on the computer
Name – names of attributes that will become field names in the database table
Type – data held in the attribute will be constrained by type (Ch3). Text, integer, Boolean, real, object, link date & time
Size – text attributes are constrained by maximum length
Required - indicates whether the field may be null
Validation- next slide

51. Data dictionary columns (cont’d)
Validation – each attribute is constrained by the range of acceptable values. 4 types of validation check:-
Presence - whether null values are allowed
Range - above/below/between certain values
Permitted values -one of a selection of values is allowed
Format - data must conform to specific pattern and/ number of characters
PK/FK – identifies primary and foreign keys

52. Data dictionary example
Table name
Field name
Key
Type
Size
Required
Validation
DVD
DVD Code PK
Integer Y
Film Code FK
Text 4
Look up the Film table
Cost
Currency
Range check >=1 and <=3
MEMBER
Member number
Title
Restricted choice
Mr/Mrs/Miss/Ms
Forename 15
.....
....

53. Order
( Order_number
Order_date
*Customer-_number)
Customer
(Customer_number
Customer_name
Address
Postcode
Telephone_no)
Order_item
( *Order_number
*Item_code
Quantity)
item
(Item_code
Description
Unit_cost)

54. Description and implementation of complex database operations
Input (forms):-
used to provide a simple form for entering data
 Query: –
used to search a database for records that match criteria
used to sort data into order
calculated field - generates its value other field(s) in a table
Output (reports):-
used to generate a printable copy of the output from a query
formatted to look good
can also sort or carry out calculations

55. Example of exam question about complex database operations
Pupil
Course
Choice
Teacher
pupil ID
course ID
pupil ID *
teacher ID
pupil name
course title
course ID*
teacher name
date of birth
level
teacher ID*
room no
register class
department
 Describe how this report was generated:-
pupil ID: 2453
course title
level
teacher name
room no
Computing Science
National 5
Mrs Forbes
B210
Business Management
Mr Brown
B209
Administration & IT
Mrs Stirling
B108

56. Answer - Description of complex database operations
“Create a query with the following fields:
Pupil.pupil ID = 2453
Course.course ID
Course.level
Teacher.teacher name
Teacher.room no
And then create a report using the data from the query”

57. Further Example of exam question about complex database operations
A report is produced each time a customer makes an order. An example is shown:-
This report is based on a query. State a list of the tables and fields that would be used in this query and any criteria that would be used to select the above data.

58. Answer - Description of complex database operations
Customer.Customer No
Order.Order No
Order.Quantity
Item.Description
Item.Unit Cost
[Customer.Customer No] = 5284

59. ... And another example of exam question about complex database operations
The report includes a single total of £ after the two subtotals. Describe how this can be done in the report
 Answer:-
SUM([Order.Qty]*[Item.Cost]) is placed in the Report Footer