Database Design
HIMA 4160
Fall 2009
House Keeping
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Assignment 4 due tonight
Assignment 5 due next Monday.
Agenda
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Database Concepts
Entity Relational Diagram (ERD)
Database == Data + Base
Transaction
Storage
Database: Definition
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A collection of data that:
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is organized
usually computer-based
represents repetitive information implicitly
primarily for transaction
supports retrieval
Is paper medical record a database?
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Yes
No
No opinion
Is Excel a database system?
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Yes
No
No Opinion
The shortcomings of a large table
Patient_ID
Patient_Name
Doctor_ID
Doctor_Name
…
1
Patient B
…
1
Doctor A
…
2
Patient C
…
1
Doctor A
…
3
Patient D
…
1
Doctor A
…
4
Patient E
…
2
Doctor B
…
5
Patient F
…
2
Doctor B
…
6
Patient G
…
2
Doctor B
…
7
Patient H
…
2
Doctor B
…
8
Patient I
…
2
Doctor B
…
…
A more relational database
Patient ID
Patient
Doctor ID
Doctor
1
Patient A
1
Doctor A
2
Patient B
2
Doctor B
3
Patient C
3
Doctor C
4
Patient D
Patient ID
4
Doctor ID
Doctor D
1
2
1
3
2
1
4
1
3
3
1
4
Database Management System (DBMS)
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A computer program for the purposes of managing
databases.
Is the basis for many applications (e.g., Electronic Health
Records, Personal Health Records).
A DBMS can host many databases
A database can be implemented in many different DBMS
systems.
Data Modeling
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Before you implement a database, you need to design the
database
Data modeling is a systematic way to help you design the
database.
Map/simplify the real world to database schema/structure.
Data Modeling
Why Data Modeling?
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Power and flexibility of database depend on data model
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Database is the realization of data model
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Evaluation of commercial products
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Communicating with vendors and IT staff
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Building your own databases
Database Analysis
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Determine User Requirements
Develop Data Models
“A conceptual data model is one that represents data
from the viewpoint of the user, independent of any
technology that will be used to implement the
model.”
A database has two parts
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Schema
Data
Stages of Data Modeling
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Conceptual Model
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Logical Model
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E-R diagram
Relational Model
Physical Model
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Database management
Database Modeling
Conceptual
Real
World
E-R
Diagram
Logical
Relational
Model
Physical
DBMS
Introduction
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Entity Relationship Modelling (ERM)
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A technique used to analyze & model the data in organizations
Using diagram to represent entities and relationship of
components in a system.
Supported by modern DBMS system.
De facto tool for database design
The Importance of Data Modeling
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Characteristics captured during data modeling
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Data are the most complex aspects of the modern
organization
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crucial in design of databases, programs, other items
facts and rules essential in assuring data integrity
Data are determined by the business rules.
Need to avoid scope creeps
Data tend to be more stable than the business
processes that use the data
Definitions
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Entity
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an aggregation of a number of data elements
each data element is an attribute of the entity
Relationship
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an association between two or more entities that is of
particular interest
Background
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Introduced by Peter Chen in ’75
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“The Entity-Relationship Model – Toward a Unified View of
Data”, ACM Transactions on Database Systems,Vol. 1, No. 1,
March 1976, Pages 9 - 36
now widely used in commercial database.
Why use ER Diagrams ?
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provides a global quick reference to an organization’s data
structures.
can be used individually to design an Information System’s
(IS) data structure.
offers a basis of consequential database design and
development.
ERD Development Process
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Identify the entities
Determine the attributes for each entity
Select the identifier for each entity
Establish the relationships between the entities
Draw an entity model
Test the relationships and the keys
Entities
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Person, place, object, event, or concept …
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Entity type
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in the user environment
about which the organization wishes to maintain data
collection of entities that share common properties or
characteristics
CAPITAL LETTERS
Entity instance
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single occurrence of an entity type
ENTITY
A Simple Example
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STUDENTs attend COURSEs that consist of many
SUBJECTs.
A single SUBJECT (i.e. English) can be studied in many
different COURSEs.
Each STUDENT may only attend one COURSE.
Identify the entities
Any physical object, event, or abstract concept
that we can record facts about.
Rule of thumbs:
a. Look for nouns
b. Not all nouns are entities
c. Some of them are attributes
Identify Entities
A football team has coaches, players, trainers and other
assistants. Coach’s roles include head coach, defense and
offence coordinators, quarterback coaches, etc.
Football players can play different positions like quarterback,
running backs, receivers etc.
Rule of thumbs:
a.
Look for nouns
b.
Not all nouns are entities
c.
Some of them are attributes
Identify Entities (my answers)
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Coach
Player
Trainer
Assistants
Roles
Positions
Attributes
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Property or characteristic of an entity type that is of
interest to the organization
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Simple or Composite?
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initial capital letter followed by lowercase letters
underscore instead of space (first_name)
composite has component parts
will users need to refer to those individual components?
Single-valued or Multivalued?
Stored or Derived?
Name
Number
PLAYER
Determine the Attributes
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Every Entity has attributes.
Attributes are characteristics that allow us to
classify/describe an entity
e.g., entity STUDENT has the attributes:
 student
number
 name
 date
of birth
 course number
Identifier [Attribute]
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“An identifier is an attribute (or combination of
attributes) that uniquely identifies individual instances
of an entity type.”
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atomic or composite
Criteria
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will not change its value
never null
unique
SS#
Name
Number
PLAYER
Key Attributes
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Certain attributes identify particular facts within an
entity, these are known as KEY attributes.
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The different types of KEY attribute are:
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Primary Key
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Composite Primary Key
Foreign Key
Key Definitions
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Primary Key:
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Composite Primary Key
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One attribute whose value can uniquely identify a
complete record (one row of data) within an entity.
A primary key that consists of two or more attribute
within an entity.
Foreign Key
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A copy of a primary key that exists in another entity for
the purpose of forming a relationship between the
entities involved.
ER Diagram Notations
Every entity diagram consists of the following components:
Entity (labelled box)
Relationship line
COURSE
Degrees of a Relationship
One-to-one (1:1)
1
1
WOMAN
MAN
One-to-many (1:n)
CUSTOMER
1
M
ORDER
Many-to-many (n:m)
M
COURSE
M
SUBJECT
NOTE: Every many to many relationship consists of two one to
many relationships working in opposite directions
Notation of Cordiality (Degree of relationship)
One-to-one (1:1)
MAN
WOMAN
One-to-many (1:n)
CUSTOMER
ORDER
Many-to-many (n:m)
Course
Subject
Notation for Optional Participation
1
PERSON
M
CAR
A person can own no or several cars. A car
doesn’t have to be owned by a person, but if
it is, it is owned 1by only one person.
optional relationship
A Sample Four Entities ER Diagram
SUBJECTS
STUDENTS
COURSES
A Student Record Entity Diagram
PROFESSORS
Exercise
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One patient can see several doctors. One doctors can
see many patients. A patient may not see a doctor at all
Exercise
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A nurse is assigned to manage an exam room.
Exercise
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A patient must have a insurance and a insurance company
can have many patients as their customer.
Exercise (complex one)
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Draw an E-R diagram to represent the data schema of a
physician office. The entities included are physicians,
patients, insurance companies, lab, medications etc.
ER Diagram Summary
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Identify the entities
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Determine the attributes for each entity
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Select the primary key for each entity
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Establish the relationships between the entities
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Draw an entity model
Logic Design and Physical Design
Conceptual Design
BED
PATIENTS
Conceptual Design
DOCTORS
PATIENTS
DOCTORS
PATIENTS
Conceptual Design
DOCTORS
PATIENTS
Conceptual Design
DOCTORS
PATIENTS
1.
2.
3.
4.
5.
6.
7.
8.
1.
2.
3.
4.
5.
6.
7.
Doctor_ID
Doctor_lname
Doctor_fname
Doctor_mi
Doctor_specialty
Doctor_address
Doctor_phone
Doctor_email
Patient_ID
Patient_lname
Patient_fname
Patient_mi
Patient_address
Patient_phone
Patient_email
Logical Model
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Entities  tables
Relationship  keys (primary and foreign)
Many to many  two one to many relationship with an
associate entity in the middle
Normalization
Conceptual Model
DOCTORS
PATIENTS
1.
2.
3.
4.
5.
6.
7.
8.
1.
2.
3.
4.
5.
6.
7.
Doctor_ID
Doctor_lname
Doctor_fname
Doctor_mi
Doctor_specialty
Doctor_address
Doctor_phone
Doctor_email
Patient_ID
Patient_lname
Patient_fname
Patient_mi
Patient_address
Patient_phone
Patient_email
Logical Model
DOCTORS
PATIENTS
1.
2.
3.
4.
5.
6.
7.
8.
1.
2.
3.
4.
5.
6.
7.
8.
Doctor_ID
Doctor_lname
Doctor_fname
Doctor_mi
Doctor_specialty
Doctor_address
Doctor_phone
Doctor_email
Patient_ID
Patient_lname
Patient_fname
Patient_mi
Patient_address
Patient_phone
Patient_email
Doctor_ID
Conceptual Model
DOCTORS
PATIENTS
1.
2.
3.
4.
5.
6.
7.
8.
1.
2.
3.
4.
5.
6.
7.
Doctor_ID
Doctor_lname
Doctor_fname
Doctor_mi
Doctor_specialty
Doctor_address
Doctor_phone
Doctor_email
Patient_ID
Patient_lname
Patient_fname
Patient_mi
Patient_address
Patient_phone
Patient_email
Associate Entity/Bridge Table
DOCTORS
D_P
PATIENTS
1.
2.
3.
4.
5.
6.
7.
8.
1. Patient_ID
2. Doctor_ID
1.
2.
3.
4.
5.
6.
7.
Doctor_ID
Doctor_lname
Doctor_fname
Doctor_mi
Doctor_specialty
Doctor_address
Doctor_phone
Doctor_email
Patient_ID
Patient_lname
Patient_fname
Patient_mi
Patient_address
Patient_phone
Patient_email
Physical Model
Relation
Table
Tuple
Row
Attribute
Column
Doctor_I
D
Doctor_ln
ame
Doctor_fa
nme
Doctor_m
i
Doctor_sp
ecialty
Doctor_a
ddress
Doctor_p
hone
1
…
…
…
…
…
…
…
2
…
…
…
…
…
…
…
3
… Patient_ID
…
001
…
…Doctor_ID
…
1
…
…
001
2
002
1
Patient_I
D
Patient_ln
003
ame
Patient_fn
ame
Patient_M
I
Patient_a
2
ddress
Patient_p
hone
Patient_e
mail
001
…
…
…
…
…
…
002
…
…
…
…
…
…
003
…
…
…
…
…
…
Doctor_e
mail
Summary on Data Modeling

Data model is the most critical aspect of system design and
function

Data models should reflect real world objects and their
relationships to ensure durability

A correct data model outlasts applications, including many
not anticipated at system start-up