1. Chapter 2 Database System Design (part II)
University of Manitoba Asper School of Business 3500 DBMS Bob Travica
Chapter 2
Database System Design
(part II)
Based on G. Post, DBMS: Designing & Building Business Applications
Updated 2020 1

2. Part-Whole Relationship: Aggregation
Sale
Item
* contains *
SaleID
SaleDate
EmployeeID
ItemID
Description
listPrice
Many-to-many relationship:
Each sale transaction contains many items, and each item can be
included in many sale transactions (provided items are keyed generically -
ItemID identifies a sort of things).
Item and Sale are loosely coupled.
SaleID is the unique key (identifies one specific sale transaction),
ItemA
ItemB
Note: This is called instance diagram
and it might help you with visualizing
multiplicity.
Sale1
Sale2
ItemC

3. Part-Whole Relationship: Composition
Two ways of displaying composition:
Wheel
WheelID
Rim
Spoke … 2
part of
Crank
CrankID
Weight
Stem
StemID
Size
Bicycle
BicycleID
Model Type 1 A
Bicycle
Size
Model Type …
Wheel
Crank
Stem B
Association between the whole class (Bicycle) and part classes (Wheel, Crank and Stem).
The whole class is composed from part classes—it does not exist without certain parts.
Parts have purpose as the parts of a specific whole—they live and die with the whole.
Therefore, part classes and whole class are tightly coupled.
Typical use: Manufacturing, bill-of-materials

4. Generalization Animal AnimalID DateBorn Name Gender ListPrice Mammal
LiiterSize
TailLength
Fish
FreshWater
ScaleCondition
Spider
Venomous
Habitat
{disjoint}
is_a
Is_a
Association between the
Superclass (Animal) and
Sub-Classes (Mammal, Fish,
Spider).
Example: Modeling data
on animals sold in a pet
store.
Superclass is parent class, and sub-class is the child class that inherits from parent.
Generalization/Specialization resembles a hierarchical classification.
Multiplicity is assumed: 1:1

5. Inheritance Concept from Object Orientated Approach
Account
AccountID
CustomerID
DateOpened
CurrentBalance
UpdateMonthly
Balance
Class name
Attributes
Methods
Class Encapsulation of
Data Attributes
Methods (Behavior)
Inheritance
Properties:
Parent class (Super-class) and Sub-classes – inheriting attributes & methods
Unique attributes and methods in sub-classes (all listed)
Polymorphism (variation of parent’s methods in children)
SavingsAccount
InterestRate
PayInterest
CheckingAccount
MinimumBalance
Overdraft
BillOverdraftFees
Polymorphism: Methods in Account may
work differently at children level.

6. Class Diagram for Pet Store System (Abbreviated): Unique & Generic Keys
Each animal keyed
uniquely.
Animal
Customer
Supplier
Merchandise
PurchaseOrder
Sale
Employee * 1
SaleItem
MerchOrderItem
Merchandise keyed
generically.
Note – differences from the textbook: Names of some classes modified.
Association names not included. Some other slight modifications.

7. Class Diagram for Pet Store System (Abbreviated): Master & Transactional Classes
Master class (M):
stable, sporadic changes
moderate amount of data M
Transactional class (T):
dynamic, frequent changes
large amount of data *
Animal *
includes 1 *
Animal
PurchaseOrder *
included in
fulfills
< handles T 1 1 M 1 M 1 * M
Supplier * 1
Employee
Sale
Customer
handles
made to 1 1 T *
handles
fulfills * *
includes
Merchandise
PurchaseOrder
MerchOrderItem T
SaleItem T * M T * *
includes
Merchandise
Note that master classes usually connect via transactional classes, not directly.

8. Pet Store Schema (Normalized Tables Diagram)
Differences from class diagram:
Associations not named
Association classes became tables related to source classes
Association between source classes disappeared

9. Data Types ("Domains") Format of data and range of values. Access
SQL Server
Oracle
Text
fixed
variable
memo
Memo
char, nchar
varchar, nvarchar
text, ntext
CHAR
VARCHAR2,NVARCHAR2
LONG
Number
Byte (8 bits)
Integer (16 bits)
Long (32 bits)
(64 bits)
Fixed precision dec.
Floating
Double floating
Cur
rency
Binary choice
Byte
Integer
Long NA
Float
Double
Currency
Yes/No
tinyint
smallint
int
bigint
decimal(p,s)
real
float
money
bit
INTEGER
NUMBER
NUMBER(127, 0)
NUMBER, FLOAT [movable dec. point]
NUMBER(38,4)
Date, Time
Date/Time
datetime s
malldatetime
DATE
Image
OLE Object
image
LONG RAW, BLOB
Auto integer
AutoNumber
Identity
rowguidcol
SEQUENCES
ROWID
Data Type
Precision (No. of digits)
Scale (No. of
decimal digits)

10. Computed Attributes Denote computed values. Written with a slash (/).
Employee
Name
DateOfBirth
/Age
Phone …
Calculated by its method, not stored:
Age=Today’s Date-DateOfBirth
(the number of seconds
from a historical start to date minus
the number of seconds from that start to
birth date)
Common example in business DB system:
Sum=Item’s Sale Price * Quantity Sold

11. Rolling Thunder Bicycles: Package View
Sales
Assembly
Purchasing
Location
Bicycle
Employee
Package = A grouping of related elements to provide
an overview of a database system.
Each package typically has more classes.
The way modern OO systems are designed and procured.

12. Rolling Thunder Bicycles: Sales Package
Customer
CustomerID
Phone
FirstName
LastName
Address
ZipCode
CityID
BalanceDue
Transaction
TransactionDate
EmployeeID
Amount
Description
Reference
Retail Store
StoreID
StoreName
ContactFirstName
ContactLastName
Bicycle::Bicycle
BicycleID …
1..1
0..*
0..1
From Bicycle package