Higher Computing Science Database Structure

2. Database Structure
 A database is a system for organising and storing data
 Databases are made up of one or more files
 Files are a collection of records, and records are made up of fields.

3. Database Structure
 A database is a system for organising and storing data
 Databases are made up of one or more files
 Files are a collection of records, and records are made up of fields.

4. Database Structure
 Each column represents a field
 Each row represents a record

5. Flat File Database
 A flat-file database is a database structure which consists of only a single
table.
 While this is a simple way to store files, a flat-file system becomes
increasingly inefficient as more data is added.

6. Database Anomalies
Whilst the flat-file database might seem to be a good solution to begin with,
there are actually a number of problems which are linked with this approach.
These are known as anomalies.

7. Database Anomalies
Anomaly 1:
Mr O'Hara is a teacher in the English department and he teaches in English
Room 4. Add Mr O'Hara's details to the database.

8. Database Anomalies
Anomaly 1:
Mr O'Hara is a teacher in the English department and he teaches in English
Room 4. Add Mr O'Hara's details to the database.
This is known as an insertion anomaly.

9. Database Anomalies
Anomaly 2:
The art department is reorganising rooms and Miss Dewar is moving from Art
Room 3 to Art Room 1. Update the database to show this.

10. Database Anomalies
Anomaly 2:
The art department is reorganising rooms and Miss Dewar is moving from Art
Room 3 to Art Room 1. Update the database to show this.
This is known as an update anomaly.

11. Database Anomalies
Anomaly 3:
John McGinn has left school. His record should be deleted from the database.

12. Database Anomalies
Anomaly 3:
John McGinn has left school. His record should be deleted from the database.
This is known as a deletion anomaly.

13. Relational Databases
A better approach to database design is known as the Relational Database
Model. In the relational model, the data is stored in multiple tables or relations.
However, in this example we have lost the link between pupil and their tutor
teacher.

14. Relational Databases
We create linked tables by introducing keys.

15. Relational Databases
We create linked tables by introducing keys.

16. Atomic Data
Data items are said to be atomic if they cannot be broken down into smaller
data items.
In this example, Forename and Surname fields are atomic because they
cannot be broken down into smaller data items:

17. Atomic Data
Data items are said to be atomic if they cannot be broken down into smaller
data items.
In this example, the Pupil Name field is not atomic because it could be further
broken down into fields - Forename and Surname: