Babysitter Example
Dimensional Modeling
Babysitter Service
The MISSA Service Club wants to run a
babysitting service. Customers call to
request a sitter and the Club Coordinator
assigns an employee to sit for the
customer from a list of employees
available for the particular day requested.
Usage
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Customers call in to request an appointment
The coordinator checks to see if the customer is
registered and enters the appointment in the
system
The coordinator finds an employee to take the
appointment
The club sends a confirmation to the employee
and the customer
Once the engagement is complete the club bills
the customer for the service.
ERD
Customer
CNumber
LastName
FirstName
Address
City
State
Zip
Phone
Job
JobNumber
ENumber
CNumber
Date
TimeBegin
TimeEnd
Rate
Notes
Employee
ENumber
ClubNumber
LastName
FirstName
Address
City
State
Zip
Phone
DaysAvailable
Club
ClubNumber
ClubName
ClubAccount
Entity Relationship Model
MINIMIZES DATA REDUNDANCY
Easier to insert, delete and update data
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Each “thing” in the system has its own table
Each row in the table is uniquely identified with a primary
key
Attributes (variables) are properties of the entity
Rows in different tables are connected by matching
primary keys
Retrievals use professionally written, sometimes
complex SQL statements
Dimensional Model
Customer
CustomerKey
LastName
FirstName
Address
City
State
Zip
Phone
Date
DateKey
SQLDate
DayName
Holiday
Job
JobNumber
EmployeeKey
CustomerKey
ClubKey
DateKey
TimeBegin
TimeEnd
Amount
Duration
Employee
EmployeeKey
ClubNumber
LastName
FirstName
Address
City
State
Zip
Phone
Club
ClubKey
ClubName
ClubAccount
Dimensional Model
MAXIMIZE RETRIEVAL EFFICIENCY
Produces simpler, faster retrievals
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One central fact table per model
 A fact
represents an event or item that the user wants
to track
 Fact data is usually numeric and additive
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Descriptive properties are connected with
dimension tables
Queries involve simple SQL code written by
users