M1G505190 Introduction to Database Development 1. Databases and Database Design

M1G505190

Introduction to Database Development

1. Databases and Database Design

Teaching staff

Jim Paterson Room [email protected]

Lab tutors: June McCrae Andreas Komninos Morteza Zanjireh Abbas Javed

Introduction to Database Development 1. Databases and Database Design#2

mailto:[email protected]

Online resources

GCU Learn Announcements Assessment information Lecture notes, lab & tutorial sheets, solutions Links to other resources


Reading

No set text – notes will be provided The following books may be useful additional

reading: Beginning Database Design: From Novice to

Professional (Clare Churcher, Apress, ISBN 1-59059-769-9)

Head First SQL (Lynn Beighley, O'Reilly, ISBN 0-596-52684-9)

Many other books on databases and SQL in the library


Assessment

Class test (30%) Hand-in assignment (70%)


What is a database?

Any collection of data can be described as a database

Computerised database systems are now very commonplace

Information is stored in a database every time we: use a bank account book a travel ticket make an appointment with a doctor etc.


Database mangement systems

A database is simply the collection of data which you need to store

To actually store the data, and to do anything useful with it, you need a Database Management System (DBMS)

A DBMS controls the way the data is stored on the computer, and provides ways of getting data in and out of the system


Data models

The way in which data is organised for storage in a database is known as the data model

Early computer databases developed in the 1960’s used a hierarchical model

Similar to the way files and folders are still organised in modern computer file systems

Most data does not fit very well into a simple hierarchy


Data models

Hierarchical data

“Real-world” data – no clear hierarchy


Relational databases

Relatively complex data like this is better handled with the relational model

Devised by Edgar Codd around 1970 Most databases nowadays are relational

databases although there are others: object databases, XML

databases, “NoSQL” databases A database management system which uses

the relational model is called an RDBMS


Databases and Enterprise Information Systems


DomainObjects

Command Objects

Web pages

Data Access Objects

Database

UI Layer

Business Layer

Database Layer

GUI

Database servers


Application

Database

Desktop PC

Database

ClientApplication

ClientApplication

ClientApplication

Desktop PC

Desktop PC

Desktop PC

Database

Web browser

Web browser

Web browser

Desktop PC

Desktop PC

Desktop PC

EnterpriseApplication

Servers

Server

Server

Desktop Application

Client-Server Application

Enterprise Web Application

network or internet connections

database accessed as file or through local serverdatabase accessed as file or through local server

database accessed through network serverdatabase accessed through network server

Popular RDBMSs

Microsoft Access aimed at small businesses, and useful for desktop applications

and systems with a small number of users

Microsoft SQL Server, Oracle, IDM DB2 scalable and secure, and widely used by large organisations

MySQL open-source and quite powerful, widely used in web sites

Microsoft SQL Server Compact, JavaDB, SQLite compact DBMSs, suitable for mobile devices in particular

...and many more


RDBMS tools

Most RDBMSs include tools to create complete application, for example: form designers – to allow data entry forms to be

created for the user interface report designers – to present data to the user stored procedures – to perform processing of

data according to business rules


RDBMS and other tools

Can use your RDBMS and its tools for everything, or

Can use the RDBMS as a component and use other tools and programming languages to create the other components

For example the GCUTours case study: data entry forms and reports are created as web

pages business logic uses Java


SQL – the language of relational databases

To develop applications which use relational databases you usually need to use SQL Structured Query Language

This is the language which is used to define queries

A query is a request to a DBMS for some specific information

Relational databases are sometimes referred to as SQL databases


SQL example

SQL queries can be quite easy to understand For example, the following query finds the

last name of all the customers in a database:

SELECT lastName FROM Customers;

SQL can also be used to add, update or delete data, and to build the database in the first place


SQL standards

SQL is supposed to be a standard language which is supported by all RDBMSs

In fact, you need to be careful because there are some important differences between the versions of SQL used by different systems Different versions of SQL standards (SQL92,

SQL99,etc.) Different implementations by RDBMS vendors


Designing a database

A well-designed database helps to make sure that the data stored is accurate and consistent and can be retrieved easily

What do we mean by inconsistencies? It would, for example, be inconsistent to store

a booking without storing the details of the customer making the booking

With careful design, we can make sure the database won’t allow this to happen


Steps in designing a database

Determining the intended uses of the system Creating a data model Implementing the database


The data model

Data model = domain model classes which represent entities we need to store permanently


-name-address-username-password-datejoined

User

-location-name-description-adultprice-childprice-departure

Package

-departuredate-offer

Tour

-adults-children-bookingdate-status

Booking

0..*

1..1

1..1 0..*

1..1 0..*

Data modelling techniques

We are using object-oriented techniques with UML to design our data model

There are other methods which are also commonly used in database design

One widely used method is called Entity Relationship Modelling (ERM)

Represents the data model as an Entity Relationship Diagram (ERD)


From data model to database

Need to consider how the data model can be represented in a specific RDBMS

This requires some further design RDBMS software has specific ways of

representing and enforcing the entities, attributes and relationships in the data model

For example, a data model entity is represented as a table in the relational database


Representing the data model in an RDBMS


Different representations

business layer for example as Java classes and objects business logic in Java methods

database layer data is stored permanently in a database system queries database to get data it needs to

carry out a particular action The system needs to map data from

database tables to classes


Documents

M1G505190 Introduction to Database Development 1. Databases and Database Design