How use PowerQuery and M to extract gold from your data

1. SQL
START!
2021
–
10°
ANNIVERSARY
The Hidden Treasure
inside Power BI
Lorenzo Vercellati

2. Lorenzo Vercellati
BI & Power BI Architect @
20 years burning on “Data Realm”
My little contribution to the community

3. Partners

4. Session Agenda
•Data is Good, PowerQuery is Better, M is Best
•PowerQuery & M Best Practices
•M is for MashUp
•M ission (Im)possible

5. M is Best

6. Data is Good
Being able to access data sources of many
different types is good
Good data are rarities

7. PowerQuery is Better
PowerQuery User Interface is
•Office like
•Easy-to-use
•Powerful
Make your data better

8. M is Best
PowerQuery covers only 40% of M power
M can simplify step sequence
M makes possible really complex
transformations
With M you can manage errors

9. PowerQuery & M Best Practices

10. Nomen - Omen

11. No Space, please!
let
Source = …….,
#”Removed Non-Key Columns” = Table.SelectColumns(Source,{…
let
Source = …….,
Removed_NonKey_Columns = Table.SelectColumns(Source,{…

12. Comment your Code

13. Formula Bar Always on
Train yourself to understand the code behind the
User Interface
Verify what you are really doing

14. M is for MashUp

15. M is a functional Language
Between let and in
One step, One function (at least)
StepName = Function(PreviousStepName, Parameters)

16. M is case sensitive
Keep in mind!
Text <> text
DAX is case insensitive
COD1 <> cod1 for M
COD1 = cod1 for DAX

17. M Fundmentals

18. M Objects
•Lists
•Records
•Tables
•Functions

19. Lists
{“Pippo”, “Pluto”, “Paperino”}
{1..10}
{{"Squadra.1", "Squadra"}, {"Squadra.2", "Schema"}}

20. Records

21. Functions
= #shared

22. M ission (Im)possible

23. Scenario
• Web page source Code
• Over 3000 rows of complicated
XML
• Data of the same match in
different tables
• It’s mandatory to have Team
Name as column not as general
header
• We need to intercept and
interpretate also icons

24. Scenario

25. Scenario

26. Time to jump into the Demo

27. Reference

28. Reference
• Chris Webb's BI Blog Chris Webb's BI Blog (crossjoin.co.uk)
• The Excelguru Blog - More geeky stuff from the author of
www.excelguru.ca...The Excelguru Blog | More geeky stuff from the
author of www.excelguru.ca…

29. Any Questions?

30. Thank You For Attending
lvercellati@lucient.com
@supergimi
LorenzoVercellati
Data Pied Piper – Medium