INTRODUCTION TO DATABASESRelational Databases

• Welcome to the module

• How the module is organized and assessed

• What YOU need to do to pass this module

• Database Fundamentals

• Summary

Outline of today’s session

MODULE DELIVERY

The module is taught with 1hr Lecture and 1 hr seminars• You must make notes in lecture• There are NO handouts given in the lectures! If you need them print

them out in advance• You are expected to do additional reading between lectures and it is

assumed that you will have done this• You MAY record the lectures provided you ASK, you may NOT video

the classes & you do not have permission to distribute the recordings.• Seminars must be attended, if you miss the seminar you WILL fall

behind, most tutors will NOT see you outside of a seminar. SEMINAR’S ARE MONITORED!

• If you do not understand ASK!

ASSESSMENT STRATEGY

This module is assessed by Exam and In-class tests (milestones) 1 exam

There is an exam worth 50% of the module grade taken in seminar slot for week 12 semester 2

4 milestones 2 in each semester (semester 1 weeks 6 and 12, semester 2 weeks 6 and

11) Each milestone is worth 12.5% Taken in seminar slots, if you miss the seminar slot you will be awarded 0 for

that milestone

Assessment marks are available immediately but the feedback is not available till the week after the assessment.

The assessments are taken online during class time. If any assessment component is failed then the module may not be progressed and a referral will be required in the summer.

AIM OF THE MODULE

To give students an understanding of the nature and use of databases within computing

Demonstrate that data is not necessarily useful in its raw from, data must be converted to information

Give students sufficient technical skills to interrogate the raw data and convert it to information

WHAT IS A DATABASE?

Common understanding of databases by students starting this module MS Access is a database Database programming involved dragging

and dropping fields with a bit of tweaking Database are not that relevant to my area

of computing The aim of this course if to rectify these

misconceptions!

WHAT IS A DATABASE?

“a collection of data that is permanently stored on a computer”

A database must be able to:• Hold different types of data in a collection• Record the relationships between the different items in the collections• Have a ranges of sizes capacity

We need to be able to:• Insert new data, delete obsolete data & amend existing data in the

collection• Retrieve data in the collection in a variety of ways• Manage the collections so that the data can be permanently stored and

protected from corruption or loss.

The quick brown fox

jumped over the lazy fox

26th August 1972

WHAT DATA CAN BE HELD?

A data collection (databases) should be able to hold a range of data types

• Images• Audio files• Text• Numerical• Date• Video• Maps• Etc.

The theory of the database is not always a reality ... This course will look at the theory AND the practical, you must understand the difference

DATABASE MANAGEMENT SYSTEMS (DBMS)

There needs to be a special piece of software to manage the database if the benefits are to be obtained

VERY complex to write so don’t want to have to write own programs to do this

Therefore, buy a Database management system (DBMS) Change the DB contents to keep them up to date Find and retrieve data from database Protect data for accidents and intruders Store in an effective way on the computer

During this course we will be using the Oracle DBMS (version 11g)

The DBMS is covered in later sessions

WHAT IS A RELATIONAL DATABASE? In reality databases hold only certain types of data in a true

relational database form we are looking at the Relational db in this course and

although we need to be aware to the theoretical possibilities we are mainly focusing on the real world situation.

A relation is just a logical structure that contains related data (hence the term relation) it is commonly referred to as table but the correct term is relation (books will use either term)

A relation/table may hold the name, address, date of birth, enrolment number of a student. All the data in one collection or row would relate to one student and all the different rows in the collection would be related to students.

WHAT IS A RELATION/TABLE?

As mentioned, all the data in a database is held in a cluster of similar data (normally similar MEANING not DATATYPE)

Name Address D of B Customer number

Esmé WeatherWax

The cottage, Lancre

0122522

Susan Sto Helit 1 South Hights Sto Helit

26/081972 2365565

In the above table, all the data would be the type of data you may find in a CUSTOMER table, we have the name, address, etc. Note: not all data is entered, some data may be optional.

First Name Surname Location Job Marital Status

Profile image

Sam Vines Ankh-Morpork Watch Commander

Married

William De Worde Ankh-Morpork Newspaper Editor

Single None available

Jason Ogg Lancre Blacksmith Married None available

Esmeralda Weatherwax Lancre Witch Single

Thomas Silverfish Ankh-Morpork Alchemist Single None available

Data can be of different formats or data types in a database, some data though may be held but not available to have all actions on them for example, a picture can be added or deleted but not updates (you can not change Esmerelda’s hat for a bonnet etc) it is more common to find the data above held as .........

First Name

Surname Location Job Marital Status

Image location

Sam Vines Ankh-Morpork

Watch Commander

Married //pictures/sam.gif

William De Worde Ankh-Morpork

Newspaper Editor

Single

Jason Ogg Lancre Blacksmith

Married

Esmeralda

Weatherwax

Lancre Witch Single //images/witch/Esmé.jpg

Thomas Silverfish Ankh-Morpork

Alchemist Single

In the above table we can see that the image has no longer been embedded into the table, instead the location of the image is displayed, this data would be used to locate the image if it is needed but the data itself remains true to the relational principles.

Same data but held in an alternative manner

DATABASE TERMS

There are various books or papers that discuss databases, and it is often confusing to find that 2 different sets of terms are used, one set RELATIONAL terminology and another SQL terminology.

Relations and datasets are normally displayed or depicted as tables so often the term TABLE is used in SQL rather than RELATION

Tables have columns and rows so most SQL terminology uses these terms Table = Relation Column = Attribute Row = Tuple

STRUCTURE OF A DATABASE (PAGE 17 OF BOOKLET)

The database is made of tables/relations and relationships.

Student ModuleProgramme

3 tables: student hold the student personal data, programme includes data on the different programme structures and module contains information on the different modules. The tables each hold data that will stand in isolation, if we need info on the BIS programme of the Games programme we look in the programme table but also the tables relate to each other, a student is enrolled on a programme and each programme has a number of modules associated with it and modules may run on a number of different programmes

Student ModuleProgramme

RELATIONSHIPS

It is important that relationships between data are clear and understood in order to get the most out of the database and its data

There are different types of relationships1 – manyMany – Many1 – 1

Normally 1 – many are the types of relationships that we need to foster

TASK (NOT INCLUDED IN YOUR BOOK SO COPY INTO YOUR NOTES!)

A company employs a number of people, the personal details such as name, address, salary and payroll number etc are held in the works database. Each employee works for a department and each department is responsible for a number of different projects.

1. What are the main clusters of data (this will give you the tables/relation)

2. What content will be in each of the identified tables/relation (this will give you the columns/attributes within the table/relation)

3. Think about how the different data relates to each other

SOLUTION

Employee

project

department

First name Surname Date of Birth

address postcode Employee number

Department number

Department name

Location Postal address

Postal postcode

project number

Project summary

Project manager

Start date Completion date

Note: When you are designing a database you need to identify the attributes/columns from the existing data or discussions with the client.

• An employee works for one department• A department has many employees• A department has many projects • A project is run by one department

SEMINAR TASKS

In the seminar you are to do Seminar task 1. Before next weeks lecture you are expected to

read all the notes in the booklet that relate to this weeks lecture (up to page 17)

Next week we are going to look at the tables/relations in more detail, how they work, what additional elements we have to include in addition to the expected attributes and what limitations they have.