Single wide extract vs multiple tables

Hi Vandana,

Thank you for the forum question.

If you want a fast reply just ask the questions without addressing a specific trainer. I am happy to answer your questions, but I may be occupied for many days and may not be apple to answer.

This is a very common question, and your instinct to pause on this is absolutely right. Short answer: yes, Power BI can handle a single wide extract, but no, it’s not best practice for a model like the one you describe.
I’ll address your questions directly and then give a clear recommendation.
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1. Is this common or straightforward in Power BI?
It’s possible, but it’s not the norm for well designed models.
Power BI (via Power Query) is very good at:
• Splitting wide tables
• Filtering by “Type” columns
• Creating multiple derived tables from one source
So technically:
• Yes, you can ingest one wide Excel file
• Yes, you can split it into Parent / Needs / Experiences tables
However:
• This approach is usually used as a last resort
• It’s more common when the source system cannot do better (e.g. fixed vendor exports)
In professional Power BI projects, separate, logical tables are far more common—especially when there is a clear parent–child structure like yours.
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2. Downsides of a single wide extract
There are several, and they tend to show up over time rather than on day one.
2.1 Model anti pattern: denormalised and sparse data
Your proposed structure creates a table where:
• Many columns are irrelevant for most rows
• Columns are conditionally populated based on Type
This leads to:
• Lots of blank values
• Poor column compression
• Inefficient storage in the VertiPaq engine
Power BI strongly prefers narrow tables with consistent meaning per column, not “sometimes this column applies, sometimes it doesn’t”.
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2.2 More complex Power Query logic
To recover a clean model, you’ll need:
• Filters on Type
• Column pruning per derived table
• Careful handling when new columns are added
That means:
• More transformation steps
• Higher maintenance risk
• Higher chance of refresh failures when the extract changes
If the provider adds a new “Experience” column, your model breaks unless someone updates the splits.
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2.3 Weaker semantic clarity
When someone opens the model:
• The lineage is harder to understand
• Business meaning is buried inside Power Query logic
• Debugging data issues takes longer
With separate source tables, the semantic intent is obvious:
“This table represents Needs; this table represents Experiences.”
With a wide extract:
“This table represents… everything, but only sometimes.”
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2.4 Performance and refresh impact
While Power BI can optimize well, wide tables cause:
• Larger memory footprint
• Slower refreshes
• Slower DAX evaluation when filters behave unexpectedly
This becomes noticeable as:
• Volume grows
• Refresh cadence increases
• Report complexity increases
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3. Best practice recommendation
Strong recommendation: push for separate logical tables
For a model like yours, separate tables/files are unequivocally better.
Ideal setup:
• Parent.xlsx (or table)
• Parent_Needs.xlsx
• Parent_Experiences.xlsx
• Other child entities
Even better (if possible):
• CSV or database tables instead of Excel
• Incremental or delta-based extracts
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Why vendors push one wide file
To be fair to the provider:
• It’s easier for them
• It reduces export logic
• It avoids questions about relationships
But this shifts data modeling complexity onto you, where it doesn’t belong.
A good principle:
The system that knows the data structure best should do the shaping.
That is the source system, not Power BI.
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If you must accept one wide extract
If pushing back isn’t possible, mitigate the damage:
1. Treat the file as a raw staging layer
o Never report directly from it
2. Split it immediately in Power Query
o One query per logical entity
3. Disable load on the raw table
4. Document assumptions
o Especially how Type drives column relevance
This is viable, but it should be framed internally as a compromise, not a design goal.
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Bottom line
Question Answer
Is it common? Possible, but not recommended
Is it straightforward? Technically yes, architecturally no
Are there downsides? Yes: performance, clarity, maintenance
Best practice? Separate tables/files, strongly preferred
If you’re early in the implementation, now is the best time to push back politely but firmly. Once reports are built, changing the source shape becomes far harder.


Kind regards

Jens Bonde
Microsoft Office Specialist Trainer

Tel: 0207 987 3777
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