Skip to main content
Showing results for 
Search instead for 
Did you mean: 

Earn a 50% discount on the DP-600 certification exam by completing the Fabric 30 Days to Learn It challenge.

Helper I
Helper I

Do merge operations like Append store data twice?

I am trying to understand how Power BI stores data.

If I append Table A to Table B to create Table C:
Does Power Query / Power BI duplicate the data from A & B to create C and  store it twice thereby doubling the size of the file / data model?

( I am asking because I cannot disable the load of my tables, as I use SSMS to load data via XMLA endpoints. This is because the dataset is to large to publish, and it times out if I attempt to refresh it using native functionality in Power BI Service)

Super User
Super User

Hi @oneraj4u 


As far as I know, you're right. It stores data twice.

Thanks for your response!  
Do you have a link to any documentation on the matter per chance?

Hi @oneraj4u 


The own documentation of Microsoft: Also, if you try to remove one of the appended tables it will give you an error. The only solution may be to apply SQL to join them before importing data into Power BI. There are lot of links on how to do it. For instance:

I appreciate your effort, unfortunately I did not see anything about the storing of data in the Microsoft documentation.
I don't have any issues or questions regarding how to Append or the behaviors, just the storage.
Thanks for your time 🙂

Just as a follow up - i use XMLA endpoints in SSMS, not SQL. 

Helpful resources


Fabric certifications survey

Certification feedback opportunity for the community.


Power BI Monthly Update - April 2024

Check out the April 2024 Power BI update to learn about new features.

April Fabric Community Update

Fabric Community Update - April 2024

Find out what's new and trending in the Fabric Community.

Top Solution Authors
Top Kudoed Authors