1: Creating a Normalised Relational Database Structure

Table of Contents

1. What is Data?
   1. Database - an Explanation
   2. Keys
   3. Summary
2. The Relational Database Model
3. The Need for Normalisation
4. Entity Model Diagrams
5. The Data Dictionary
6. Creating the Database Tables

Database - an Explanation

Let us continue with the DVD example from the previous screen. Imagine you have created, perhaps on individual cards, a record for each DVD in your collection. There is a lot of information held in that set of cards and it would be very useful if we could interrogate it easily. For example we could "ask" our set of cards some questions such as:

"Give me a list of all movie titles in my collection".

"Give me a list of all movies directed by Stanley Kubrick".

"Who directed Alien?"

"What films has Marlon Brando appeared in?"

"Give me a list of all films with runtime greater than 120 minutes"

"What science fiction films do I have directed by Ridley Scott?

The problem we have is accessing the information in our set of cards quickly and easily. You will appreciate that to answer the queries above we would probably have to read every card in the collection in order to ensure that the query was successful. This could be very time-consuming if you have a large DVD collection.

Next: Keys