Recap
So far so good we are about to
complete Part 1 that was very much
based on Database Concepts.
Now we are heading towards the
Design Concepts and you will have a
flavor of Implementation as most of
you do want to bring laptops ;) and
this will happen next week.
Aim for Today
 In this session you will learn;
 The Evolution of Data Models “This is
quite an interesting topic as you will
come to know how this advancement
took place in Data Base Systems”
The Evolution of Data
Models
 We all know that in the initial phases there
were short comings in the file system.
 Because of this issue the school of thought
had to shuffle their brains to come up with a
comprehensive solution.
 The models represents what a database is?
What should it do and type of structures that
it should employ.
Some Examples
 I want to share some information with you all, last
night I was reading an article by Infinite Group Ltd
that is one of the leading field marketing agencies in
United Kingdom and Europe. They gathered some of
the information that sounds very interested to me.
 Just have a look how those databases looked like in
the initial phases that many people now can’t live
without using them.
The Hierarchical Model
 It was developed to manage the large amount of data
for complex manufacturing projects. This model was
presented for Apollo Rocket that was landed on the
moon in 1969.
 You must know that what is a Hierarchy? Logically
and Practically.
 It consists of levels or segments that is very much
based on File System.
 Can you challenge your brain and come up with a
real time environment for this model? I am sure you
will.
Constraint
This model can only be used in one
type of environment that is 1:M
It might be ideal for this
environment
but
can
an
organization of this modern era
survive on a model just based on
this model?
The Network Model
 To represent complex data relationships more
effectively The Network Model was created.
 Though it is based on Hierarchical Model but
the modification is it allows a record to have
more than one parent.
 Though the Network Model is not currently
used
in
the
modern
sophisticated
environment but still some important
concepts are still used and they are;
Concepts of Network
Model
 The schema which is the conceptual organization of the
entire database as viewed by the database administrator.
 The subschema defines the portion of the database seen by
the application programmers.
 A data management language DML that defines the
environment in which data can be managed and to work
with the data in the data base.
 A schema data definition language DDL which enables
the database admin to define the schema components.
Constraint
 Can you imagine why Network Model
became too cumbersome?
 The problem is for the programmers to
generate even the simple reports
because of the lack of ad hoc query
capability.
Ad hoc Queries
 What is a query? It is a question that you ask a
database in the form of SQL Statement.
 When software developers develop any software they
define certain queries as reports, forms or accessible
via the query window.
 Ad hoc queries are those that are not defined as they
are not needed on regular basis so the user can create
their own scope outside the scope of the delivered
software.
The Relational Model
 Historically it was introduces in 1970 by E.F. Codd
of IBM.
 There will be more discussion in the coming chapter
but for the time being you can use an analogy “This
very model produced an automatic transmission
database to replace the standard transmission
database”.
The Relational Model
 It is a mathematical concept known as
relation.
 Just think about rows and columns in a Table
as a relation and tables can be simplified
using matrix.
 In short you map the data more effectively
and efficiently and mathematical formulas
are defined to explain the relations.
Constraint
 Yes you can introduce the simplicity in defining the
relations but at the expense of computer overhead.
 But this issue doesn’t exist now as you have so many
powerful systems that do have the capacity and
ability to tackle massive information. Just think
about Pentium 1 and Windows 98 and now Windows
8 Business Editions and powerful tools like Oracle,
My SQL etc.
Implementation of RDM
 The implementation is via a very strong
and sophisticated relational database
management system, basic functions are
used from the previous two models (Can
you name them?) and in addition to a host
of other functions as well.
 The most important function of RDBMS
is to hide the complexity to end user from
the relational model.
How to Relate Tables
 They are related through the sharing of common
attribute (value in a column) for example in the
figure the table is linked via AGENT_CODE that
exists in both the Customer and Agent Table.
 Even both Customer and Agent have different tables
but still they are linked. In complex scenarios data
can be handled more effectively and efficiently.
A relational Diagram
Relational Diagram
 A relational diagram is a representation of Database
entities, the attributes within those entities and the
relationship between those entities.
 In the previous figure can you explain what
relationship type has been used.
 NB: The symbol to indicate many is Infinity.
Table and File: Difference
 As a relational table stores a collection of related
entities, in this respect it is very much similar to a
File.
 The critical difference between a file and a table is
that “A table yields complete data and structure
independence as it is purely logical. How the data is
physically stored is of no concern to user all we need
as a user is end result”
 SQL is based on what it does instead of How it do
that is called an Abstraction and you all know why
Abstraction is important.
SQL based Relational
Database Application
 Involves three parts;
1. The End User Interface
Allows the end user to interact with the data by
auto generating SQL Code.
2. A collection of Tables stored in the Database
3. SQL Engine
Hidden from the end user and executes all
queries or data requests.
The Entity Relation Model
 Yes, the Relational database model has
an edge on the HM and NM but the
problem arise when the architecture of
a Database is complex and data
handling is difficult.
 In order to represent things graphically
the Entity Relationship ER Model has
become a widely accepted standard for
data modeling.
ER Model
 Peter Chan introduced this model in
1976 and it gain the popularity as it
complements the Relational Model.
 The Entities and Relationships are
represented
by
ERD,
Entity
Relationship Diagram.
ER Components
 Based on Entities and Relationships, You
must know what is an Entity and
Relationship.
 We will just focus on how to represent the
Entities and Relationship in ER Models.
 In ERD the entity is represented as a
Rectangle also known as an entity box.
 It is written in CAPTIAL letters and
singular forms as an example PAINTER
instead of PAINTERS.
Relationships
 Can you remind what can be the business
rules, what are the examples of Relationships
and how they are represented.
 Hint: Three types of Relationships?
 If you can all write the three relationships
and how they are represented and one
example from each relationship.
Connectivity
 An interesting aspect is how to label the
relationship types, this is known as
Connectivity in ER Diagram.
 Two types of notations are used while
designing the ERD.
1. The Chen Notation by Peter Chan.
2. The Crow’s foot Notation.
Information
 Just to give you some information that
Many to Many relationships exists in
the conceptual level. You should know
how to recognize them you will learn at
later stages that these relationships are
not appropriate for relational models.
The Conceptual Model
 Can you make a Blueprint or ERD for a Tiny College
that must have the following tables.
 Professor, Course, Class, Student, Enroll and Room?
 Each entity must have tables but for the time being
you don’t have to worry just try to make a sketch of a
tiny college.
 Try to make a logic and try to connect them. You can
use the crow’s foot notation.
Reminder
 If you are interested to explore some of the tactical
work you can send your Resume to infinite field
marketing Ltd. There website is;
http://www.infinitegroup.co.uk
Incase if you apply good luck  might be difficult but
not impossible as “hard work is the key to success”.