1. Lesson Objectives
Aims You should know about: 1.3.2: (a) indexing (d) SQL – Interpret and Modify (e) Referential integrity (f) Transaction processing, ACID (Atomicity, Consistency, Isolation, Durability), record locking and redundancy.

2. Referential Integrity
In a relational database every foreign key must correspond to the primary key in another table.
In other words, every link must point to a record that actually exists
If it doesn’t, there’s a problem… this is called an “orphan record”

3. Transaction Processing
Transaction processing means taking multiple smaller operations and grouping them together in a single ‘transaction’ operation.
If any of the smaller operations fails then the transaction as a whole must fail.
The aim of transaction processing is to ensure that complex operations are not left partially complete by hardware or software failures.
For example, imagine transferring £ from one bank account to another. This operation is made up of two smaller ones
Removing £ from one account
Adding £ to another
If either of these smaller operations is not successful, the operation as a whole must fail, otherwise £12,000 just vanished…

4. ACID
There are four properties of a successful transaction: atomicity, consistency, isolation, and durability (ACID):
Atomicity: either every part of the transaction is successful or none is.
Consistency: all parts of the transaction must be in line with the database rules; for example, they do not create duplicate keys.
Isolation: ensures that even if different transactions are happening at the same time, the results are the same as if they were happening one after the other.
Durability: once a transaction has been successfully completed, its actions are not undone.

5. SQL
Structured Query Language
This is the language used to manipulate data in a database
It is incredibly powerful and can retrieve data based on rules from many tables at once

6. You are expected to know…
SELECT
FROM (* wildcard)
WHERE
LIKE (% wildcard)
AND OR
DELETE
INSERT
DROP
JOIN

7. Example SELECT * FROM People WHERE Surname = “Chunder” Results:ID
Surname
Forename
Age
Height 1
Jones
Jack 67
167 2
Chunder
Captain 83
178 3
Mandela
Nelson 42
175
SELECT * FROM People WHERE Surname = “Chunder”
Results: 2
Chunder
Captain 83
178
SELECT Surname, Age FROM People WHERE Surname = “Chunder”
Results:
Chunder 83

8. Your turn
The best way to learn any language is to practise it:
Complete the lessons!

9. Review/Success Criteria
You should know:
How to read/write simple SQL statements