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M1G505190
Introduction to Database
Development
1. Databases and Database Design
Teaching staff
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Jim Paterson
Room M628
[email protected]
Lab tutors:
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June McCrae
Andreas Komninos
Morteza Zanjireh
Abbas Javed
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Online resources
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GCU Learn
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Announcements
Assessment information
Lecture notes, lab & tutorial sheets, solutions
Links to other resources
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Reading
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No set text – notes will be provided
The following books may be useful additional
reading:
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Beginning Database Design: From Novice to
Professional (Clare Churcher, Apress, ISBN 159059-769-9)
Head First SQL (Lynn Beighley, O'Reilly, ISBN 0596-52684-9)
Many other books on databases and SQL in
the library
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Assessment
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Class test (30%)
Hand-in assignment (70%)
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What is a database?
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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:
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use a bank account
book a travel ticket
make an appointment with a doctor
etc.
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Database mangement systems
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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
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Data models
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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
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Data models
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Hierarchical data
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“Real-world” data – no clear hierarchy
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Relational databases
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Relatively complex data like this is better
handled with the relational model
Devised by Edgar Codd around 1970
Most databases nowadays are relational
databases
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although there are others: object databases, XML
databases, “NoSQL” databases
A database management system which uses
the relational model is called an RDBMS
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Databases and Enterprise
Information Systems
Web pages
UI Layer
GUI
Command
Objects
Domain
Objects
Data Access
Objects
Database
Business Layer
Database Layer
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Database servers
database accessed as file or
through local server
Desktop PC
Application
Database
Desktop Application
Desktop PC
Client
Application
network or internet
connections
Server
Desktop PC
Client
Application
Desktop PC
Database
Client-Server Application
database accessed through
network server
Client
Application
Web browser
Desktop PC
Servers
Web browser
Desktop PC
Enterprise
Application
Server
Database
Enterprise Web Application
Web browser
Desktop PC
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Popular RDBMSs
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Microsoft Access
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Microsoft SQL Server, Oracle, IDM DB2
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open-source and quite powerful, widely used in web sites
Microsoft SQL Server Compact, JavaDB, SQLite
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scalable and secure, and widely used by large organisations
MySQL
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aimed at small businesses, and useful for desktop applications
and systems with a small number of users
compact DBMSs, suitable for mobile devices in particular
...and many more
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RDBMS tools
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Most RDBMSs include tools to create
complete application, for example:
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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
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RDBMS and other tools
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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:
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data entry forms and reports are created as web
pages
business logic uses Java
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SQL – the language of relational
databases
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To develop applications which use relational
databases you usually need to use SQL
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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
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SQL example
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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;
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SQL can also be used to add, update or
delete data, and to build the database in the
first place
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SQL standards
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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
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Different versions of SQL standards (SQL92,
SQL99,etc.)
Different implementations by RDBMS vendors
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Designing a database
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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
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Steps in designing a database
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Determining the intended uses of the system
Creating a data model
Implementing the database
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The data model
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Data model = domain model classes which
represent entities we need to store
permanently
User
-name
-address
-username
-password
-datejoined
Booking
1..1
0..*
-adults
-children
-bookingdate
-status
0..*
1..1
Package
-location
-name
-description
-adultprice
-childprice
-departure
Introduction to Database Development
Tour
-departuredate
-offer
1..1
0..*
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Data modelling techniques
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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)
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From data model to database
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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
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Representing the data model
in an RDBMS
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Different representations
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business layer
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database layer
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for example as Java classes and objects
business logic in Java methods
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
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