1. Lesson 10
Databases

2. We Are Learning Today
Describe a database as a persistent organised store of data
Explain the use of data handling software to create, maintain and interrogate a database

3. What is a database?
Go and list 5 databases that we use in our everyday lives..... 1 2 3 4 5

4. What is a database? A database is a store of data that is
persistent – it is held on some form of permanent medium such as a disk or flash memory
related – the data in a database is not just a haphazard collection of facts
organised – the data is stored in a structured predictable way so that it can be more easily processed
usually held for the benefit of some organisation – all businesses and other organisations depend on their stored data

5. Database levels A database can be viewed at three levels:
The external view
The conceptual view
The physical view

6. The external view
This is what the user sees. It is a view that is designed to be useful for a particular job.

7. The conceptual view
This is concerned with how the data is organised. It has to do with the design of the tables and how they are linked.

8. The physical view
This is concerned with how the data is actually stored on the storage medium.
The designers and the users of the database are not concerned with this detail. It is looked after by the database software.

9. Types of databases Flat file – we will look at one....
Relational – Used in the main by most businesses
Hierarchical – not really used now, but do exist!!!

10. Elements of a database Entity Attributes Record Field
Note down the following in your books!!!

11. Learning Activity
Produce a mind map of the previous terms and explain them in more detail.
Entity
Attributes
Record
Field
HINT: Use the emindmaps software to produce this.

12. Learning Activity Take the file out of the shared files....
You will complete the presentation on Database Concepts

13. Flat File Databases Consist of only table
Example would be a personal address book:
fairly small
Stores few items
Fields could be:
First_name
Address_1
Telephone_No
Record is when we have a full set of data about that person
Could be set up easily in a spreadsheet

14. Example Flat File First Name Last Name Telephone Street City Postcode
DOB
Claire
Pate
404 Morbi Road
Southampton
SO528GD
28/06/1999
Susan
Landry
32 Nullam Road
SO555GF
05/04/1978
Brian
Hodge
541 Sed Avenue
SO123YW
26/01/1999
Noelle
Hewitt
704 Varius Street
SO10 7NJ
04/08/1994
David
Goff
97 Primrose Close
SO552AW
30/01/1998

15. Task Possibly a definition of what a flat file database is
List the advantages and disadvantages of using flat file databases
Set up an example mark book for this class – either in Access or Excel

16. Data Redundancy What is it? What can this cause? Examples…
The unnecessary repetition of data
What can this cause?
Complex processing problems because each time a piece of data is repeated each instance has to be updated.
Examples…
Come up with one!

17. Data Integrity, validation and verification
Data Integrity is – the state of data being as it should be, it is what it should be!
Validation is – the process of checking data as it is input to ensure that it is reasonable
Verification is – the process of checking that data is true or correct

18. Validation
This type of checking is carried out by data handling software
It is useful for when data is copied into the computer systems by human operators
It does not prevent all errors, just the breaking of the rules!

19. Verification
Verification quite often can only be performed by human inspection
It can be as simple as just carefully comparing what is entered in the database with the source material.
Humans make errors too easily – so is slower more reliable method is to enter the data twice using two operators
It compares then highlights any differences

20. Task
Using the worksheet on Validation and Verification complete the following:
Research the different types of validation checks explaining what each is and how it works
Explain what each machine used to enter data is and a benefit and limitation of it

21. Lesson 12
Relational Databases

22. We Are Learning Today
Understand the relationship between entities and tables.
Understand the components of a relational database, such as; tables, forms, queries, reports and modules.
Understand the use of logical operators in a database.

23. What is a relational database?
Stores data in tables
Each table contains data about one entity
A table is called a relation

24. How are tables linked? Primary keys – we will look at what they are
Foreign keys – we will look at what these are

25. The Employee Table
Which columns acts as primary and which as foreign keys?

26. Example of a Relational Database Diagram
pub_id
job_id
Publishers --
pub_id
Jobs --
job_id
Highlight the primary and foreign keys
emp_id
Employee --
emp_id
pub_id
job_id
pub_id
job_id

27. Entity Relationships
Data about different entities needs to be kept separate
Tables are linked together to keep data duplication at a minimum
Linking tables in a ONE –TO-MANY way avoids data redundancy
Cats and fleas (example from book!)
Cat
Flea

28. Entity Relations Cat Flea
A cat has many fleas, but a flea can only have one cat.
Think of three more examples of this.
Get ready to feedback to the class.

29. Entity Relationship Diagram
Connections with “crows feet”
Three prongs means MANY
One prong means ONE
Cat
Flea

30. The DBMS The DBMS must allow data sharing allow multiple user access
allow multiple applications to work on them
hold just one copy of data that everyone can access – this prevents inconsistent updates
make it possible to change the data in a database without having to change the applications.

31. Referential integrity
Different applications must not cause conflicts.
Records must be locked while one application is performing an update so that another application cannot produce an inconsistent result.
Inconsistent changes must be prevented – for example , an exam subject must not be deleted if there are students connected to it. This is called maintaining referential integrity.

32. Realistic Example – Hotel Booking
What needs to be included?
What would the relationships be?
Tables we will have:
Room
Booking
Client

33. Task Make a list of field names we will need in each table: Room
Booking
Client
Field
Datatype
Room_number
Integer (number)
Room_type
Text
View
Boolean
Bath TV

34. Relational Databases Stores data in tables
Each table has data about ONE entity
A table is called a RELATION
Table has attributes, as fields
Rows which are records
Each table has to have a primary key
Tables are LINKED using PRIMARY and FOREIGN keys

35. Concurrency Locking of a file
Where might you use this? Note down in books
Read through this on page 103