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Cardinality Error

Hi, i am not able to connect the 3 tables i have.  gettign the following error: 

failed to save modifications to the server. Error returned: 'Relationship 'd1259967-03f1a-b4a5-f83344f5d47'..." between columns ' MAS[Part_Num]' and 'Table B[Cl_Part]' has the TO end cardinality set to Many. To end cardinality must always be set to One.

Part_Num column has Ids like below: 

Frequent Visitor



I had the same error,


I solved it by removing any 'null' items in your unique list.


Hope it helps,



New Member


I faced the same issue.


I did import data from Excel workbook and found that there was fault in my excel workbook itself.

Try correcting relationships at the source, it did solve my issue.


Error at the source usually happens when you extract data to excel directly from custom application(ERP/etc).



Kartik =

Community Champion
Community Champion

it seems you try to set up Many to Many relationship, Power BI supports One to Many & One to One relationships

Did I answer your question? Mark my post as a solution!
Thank you for the kudos 🙂



But doesn't Power BI give an explicit message when you try to do that? This must be something else. 

Community Champion
Community Champion

well it did give the error - could it be that the in desktop version it's 1 to many, while in the service dataset is bigger and it becomes many to many?

Did I answer your question? Mark my post as a solution!
Thank you for the kudos 🙂

My bridge table has primary unique key which is connecting to corresponding keys in 2 seperate tables. there are certain rows on both tables with distinct values (in one but not on other). My goal is to compare the fields of one table to those on the other. 

then create a result column that calls out; which cell values are not a match.

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