Relational databases

From MAPH09_2
Revision as of 17:23, 5 November 2009 by Sbrown (Talk | contribs)

Jump to: navigation, search
Erpshome.jpg

Required reading

Geekgirls.com databases: Database design from scratch. Step by step guides to designing and building databases including tutorials and exercises [1].

The guidance notes on Base: http://documentation.openoffice.org/manuals/userguide3/0108GS3-GettingStartedWithBase.pdf

This next reference refers to 'normalisation' http://www.island-data.com/downloads/papers/normalization.html. Read down to and including 'First Normal Form' to understand what normalisation is and why it is so important in relational database systems.

The 'Entity-Relationship' model is the first thing to build when designing a database: please read this short introduction (down to 'Diagramming conventions') http://en.wikipedia.org/wiki/E-R_diagram

Introduction

So far we have been working with a small, simple data set but useful research resources are often larger and more complex than this. See for example the Correspondence of William Henry Fox Talbot at http://foxtalbot.dmu.ac.uk or Exhibitions of the Royal Photographic Society Web site at http://erps.dmu.ac.uk. Collections like these are more difficult to manage in a single table and it's much harder to sort through all the information they contain to find what you are looking for or to see connections between different bits without some additional help. In this session you will learn how to use "relational" databases to manage large/complex sets of information and you will have the opportunity to model a small relational database.


Learning outcomes

By the end of this session you will be able to:

Explain the differences betwen "flat" and "relational" databases.

Break a set of information down into distinct "entities" and justify your decisions.

Create a diagram that illustrates the relationships between the different "entities" in your data.

Use the diagram to construct a set of interlinked tables.


To help you learn how to do this you have access to the Geekgirls.com databases tutorials dealing with: Database design from scratch [2].


Activity: Adding page scans to your Fenton database

We have page scans of all of the letters in the two letterbooks. In this activity you are going to develop further the simple flat file database of Roger Fenton's Crimean War letters you built in the previous session by adding some of these page scans.

Opening up your Fenton Letters database in Base, build another table to contain the page scan images and link it to the Letters table.

Populate this table with some of the page scans we will provide you with on a disc.

Draw a simple entity-relationship diagram to desccribe your Fenton Letters database.

Activity: Adding photographs to your Fenton database

Now that you have got the hang of drawing E-R diagrams and linking tables in a database we are going to try something a little more complicated to produce something rather more useful. This time you are going to add images of Fenton's photographs relating to the letters. There is a good online collection of Fenton pictures on the Library of Congress Website. Click on the link to "View all the images" at http://www.loc.gov/rr/print/coll/251_fen.html. Some of the people, places and events depicted in these pictures are referred to in Fenton's letters. It may be possible to match more than one picture to a given letter. It may also be possible to match more than one letter to the same picture.

Build a simple entity-relationship diagram of your Fenton Letters database.

Then, opening up your Fenton Letters database in Base, build and populate another table to hold images and a description of them, using the thumbnails from the Library of Congress site, so that one letter can link to more than one image and vice versa.

Identify the primary and foreign keys and be prepared to explain the difference between these in your seminar presentation.


Update your E-R diagram to describe all three tables.

2. Take a look at http://erps.dmu.ac.uk.

Examine this site and develop the E-R diagrams for each of the main components (exhibits, exhibitions, judges and exhibitors). Be as comprehensive as possible regarding the attributes of any entities you identify.

Select 2 of the main entities and describe the database tables diagrammatically. Identify primary and foreign keys.

Seminar preparation

Prepare a brief presentation (maximum 5 wiki pages or Powerpoint slides, not counting references) on what you have done and what you have learned from this session.


Follow this link to the Photography Resources in a Digital Age Contents page to return to the module contents.

Back to the MA: Photographic History Main Page to return to the Course contents.