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Survey on Database Architectures
A. Bacioccola
©2007, University of Pisa, Dip. Ingegneria dell’Informazione – Andrea Bacioccola
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Outlines

Desktop Database Application

Client / Server Architecture

Client / Server Database

PostgreSQL
©2007, University of Pisa, Dip. Ingegneria dell’Informazione – Andrea Bacioccola
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Desktop Database Application (1)

A desktop database is used by small businesses, and hobby
programmers to create ad-hoc customized desktop systems for
handling the creation and manipulation of data;

An example of desktop dabatase is Office Access, previously known as
Microsoft Access.

Access allows relatively quick development because all database
tables, queries, forms, and reports are stored in the database. For
query development, Access utilizes the Query Design Grid, a graphical
user interface that allows users to create queries without knowledge of
the SQL programming language.
©2007, University of Pisa, Dip. Ingegneria dell’Informazione – Andrea Bacioccola
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Desktop Database Application (2)

In the Query Design Grid, users can "show" the source tables of the
query and select the fields they want returned by clicking and
dragging them into the grid. Joins can be created by clicking and
dragging fields in tables to fields in other tables.

Access allows users to view and manipulate the SQL code if desired.

Access can be applied to small projects which involve more than one
user. In this scenario, it scales poorly to larger projects involving
multiple concurrent users because it is a desktop application, not a
true client-server database.

When a Microsoft Access database is shared by multiple concurrent
users, processing speed suffers. The effect is dramatic when there are
more than a few users or if the processing demands of any of the
users are high.
©2007, University of Pisa, Dip. Ingegneria dell’Informazione – Andrea Bacioccola
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Client / Server Architecture (1)

Client server is network architecture which separates a client (often
an application that uses a graphical user interface) from a server.

Each instance of the client software can send requests to a server.

Specific types of servers include web servers, application servers, file
servers, terminal servers, and mail servers.

While their purposes vary somewhat,
the basic architecture remains the same.
Server
Data
Re
qu
es
t
Client
©2007, University of Pisa, Dip. Ingegneria dell’Informazione – Andrea Bacioccola
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Client / Server Architecture (2)

Although this idea is applied in a variety of ways, on many different
kinds of applications, the easiest example to visualize is the current
use of web pages on the internet.

For example, if you are reading an article on Wikipedia, your computer
and web browser would be considered a client, and the computers,
databases, and applications that make up Wikipedia would be
considered the server.

When your web browser requests a particular article from Wikipedia,
the Wikipedia server finds all of the information required to display the
article in the Wikipedia database, assembles it into a web page, and
sends it back to your web browser for you to look at.
©2007, University of Pisa, Dip. Ingegneria dell’Informazione – Andrea Bacioccola
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Client / Server Database (1)

Advantages of Client/Server database over desktop Database:


Scalability: the client/server database architecture allows more than one
user to concurrently access the database; all the accesses to the
database are efficiently managed by the server;
Security: Access control techniques can be implemented. Only authorized
users can write the database;
Server


Robustness : database server applications
typically implement strategies against
hardware failures and data loss.
Portability: the client applications does
not have to implement the whole database
structure, but only methods to retrieve data.
R e su
Qu
e
lts
ry
Client
©2007, University of Pisa, Dip. Ingegneria dell’Informazione – Andrea Bacioccola
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Client / Server Database (2)

Disadvantages of Client/Server database over desktop Database:

Complexity: the client/server database requires more effort to be
implemented and managed compared to the desktop Database;
©2007, University of Pisa, Dip. Ingegneria dell’Informazione – Andrea Bacioccola
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PostgreSQL

PostgreSQL is a free software object-relational database management
system (ORDBMS), released under a BSD-style license.

It offers an alternative to other database systems. Similarly to other free
software projects such as Apache, GNU/Linux, and MediaWiki, PostgreSQL
is not controlled by any single company, but relies on a global community
of developers and companies to develop it.
PostgreSQL
Server
R e su
Qu
e
lts
ry
Client
©2007, University of Pisa, Dip. Ingegneria dell’Informazione – Andrea Bacioccola
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Data Types Comparison
Access
SQL-Server
MySQL
boolean
integer
Yes/No
Number
(integer)
Bit
Int
float
Number
(single)
Currency
N/A
Float
Real
Money
Char
N/A
Int
Integer
(synonyms)
Float
Text (<256)
Memo
(65k+)
Varchar
currency
string
(fixed)
string
(variable)
©2007, University of Pisa, Dip. Ingegneria dell’Informazione – Andrea Bacioccola
PostgreS
QL
Boolean
Integer
Int
Numeric
N/A
Char
Money
Char
Varchar
Varchar
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References

Wikipedia: http://en.wikipedia.org/
Index terms:





Database
Client-server
Postgresql
Microsoft Access
PostgreSql: http://www.postgresql.org/
©2007, University of Pisa, Dip. Ingegneria dell’Informazione – Andrea Bacioccola
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DISCUSSION
©2007, University of Pisa, Dip. Ingegneria dell’Informazione – Andrea Bacioccola
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