Context Social Enterprise, from a neighboring country which provides ambulatory services, has collected data on road accidents and is keen to use the data to inform on its resource deployment. It has stored the data into three files: ‘Accidents.xlsx’, ‘Casualties.xlsx’ and ‘Vehicles.txt’ Objective Create a data warehouse containing meaningful information on road accidents Strategies 1. Import file and transform data 2. Create queries as a new table 3. Merge these tables 4. Summary table 5. Power Pivot and create a data model

1. CREATING DATA WAREHOUSE
USING POWER QUERY & POWER PIVOT
DATA WAREHOUSE OF MEANINGFUL INFORMATION ON ROAD ACCIDENTS
Author: Anthony Mok
Date: 18 Nov 2023
Email: xxiaohao@yahoo.com

2. WHAT IS POWER QUERY & POWER PIVOT
Excel Power Query
A data
transformation and
preparation tool
that simplifies the
process of
importing, shaping,
and analysing data
from various
sources
Excel Power Pivot
A data modeling
add-in for Excel
that enables us to
create
sophisticated data
models, analyse
large datasets, and
perform complex
calculations

3. PROJECT’S CONTEXT, OBJECTIVE & STRATEGIES
Context
Social Enterprise, from a neighboring
country which provides ambulatory
services, has collected data on road
accidents and is keen to use the data
to inform on its resource deployment.
It has stored the data into three files:
‘Accidents.xlsx’, ‘Casualties.xlsx’ and
‘Vehicles.txt’
Objective
Create a data warehouse
containing meaningful
information on road
accidents
Strategies
 Import file and transform
data
 Create queries as a new
table
 Merge these tables
 Summary table
 Power Pivot and create a
data model

4. IMPORT 1ST FILE, TRANSFORM DATA & CREATE 1ST POWER QUERY
 The file: ‘data warehouse on road
accidents.xlsx’, was created in MS Excel, and
the ‘Accidents0515 sheet’ from the
‘Accidents.xlsx’ file was imported into this
data warehouse.xlsx file to conduct data
transformation
 In the ‘Day_of_Week’ column, in the
‘Accidents0515 sheet’, records with value of
-1 were excluded since this is an impossible
value
 Format of the ‘Date’ column was changed to
text since this is not a numerical data
 In the ‘Speed_limit’ column, only records that
are 40 and above were selected
 When loading the ‘Accidents0515’ sheet into
Power Pivot, ‘Only Create Connection’ option
was chosen since this would be combined
with the 2nd Power Query to form a new query

5. IMPORT 2ND FILE, TRANSFORM DATA & CREATE 2ND POWER QUERY
▪ The ‘Vehicles.xlsx’ file was imported
into the MS Excel file: ‘data warehouse
on road accidents.xlsx’
▪ Records with value of -1 in the
‘Age_of_Vehicle’ and ‘Age_of_Driver’
columns were excluded since this is an
impossible value
 When loading the ‘Vehicles0515’ sheet
into Power Pivot, ‘Only Create
Connection’ option was chosen since
this would be combined with the 1st
Power Query already created to form a
new combined query

6. MERGE TWO QUERIES TO CREATE NEW COMBINED POWER QUERY
▪ The ‘Accident0515’ and ‘Vehicle0515’
queries were merged to create the new
‘Vehicles with Accident History’ query
▪ The ‘Accident_index’ was used as the
key to merge these two queries
▪ When loading the ‘Vehicles with
Accident History’ table, ‘Only Create
Connection’ option was chosen since
there is one more Power Query to
create before loading these 3 queries
into Power Pivot as a data model

7. PREPARE SUMMARY TABLE TO CREATE FINAL POWER QUERY
▪ The ‘Casualties.xlsx’ file was imported into the
MS Excel file: ‘data warehouse on road
accidents.xlsx’
▪ The ‘Summary Table of Total Pedestrian Cases
By Casualty Severity Types’ was prepared,
through Power Pivot, with the following columns:
▪ Total Number of Accidents
▪ Average Age of Casualty (using the variable:
‘Age_of_Casualty’)
▪ Total Pedestrian Cases (using the variable:
‘Pedestrian Indicator’) for each
‘Casualty_Severity’ type (using the variable:
‘Casualty_Severity’)
▪ When loading the “Casualties0515” sheet, ‘Only
Create Connection’ option was chosen since this
is the final Power Query to create before loading
this and two previously created queries into
Power Pivot as a data model

8. CREATE DATA MODEL FROM 3 POWER QUERIES
Loading Power Queries into
Power Pivot as Data Model
The ‘Accidents 0515’, ‘vehicles05151 and
‘causalities0515’ Power Queries were loaded into
Power Pivot as a data model
Excel Power Pivot
To complete the data modelling process, at the Diagram View module in
the Power Pivot workspace, the four tables were linked, using the:
 ‘Accident_index’ key for the ‘Accidents 0515’, ‘vehicles0515’ and
‘causalities0515’ tables,
 ‘Vehicle_Type’ key for the ‘vehicles0515’ and ‘Vehicle_Description’
tables (the “F1” key in the ‘Vehicle_Description’ table is the
‘Vehicle_Type’ key)

9. CREATING DATA WAREHOUSE
USING POWER QUERY & POWER PIVOT
DATA WAREHOUSE OF MEANINGFUL INFORMATION ON ROAD ACCIDENTS
Author: Anthony Mok
Date: 18 Nov 2023
Email: xxiaohao@yahoo.com