Question related to modelling in power bi

[SurakshaKhurana]

This post is more like a question/issue that I faced and I am looking for a solution.

I have 2 data sheets in Excel say sheet 1 and sheet 2, now when I am trying to create model using these and managing relationship

I am trying From Sheet 1 to Sheet 2 using one to many but when I am trying to save it. It is coming as From Sheet 2 to Sheet 1 many to one. I tried this like 10 times still facing this issue.

Kindly help

[rohit1991 · Accepted solution]

Hii @SurakshaKhurana 

Power BI does not let you force a One-to-Many relationship manually it decides it based on data uniqueness. The table on the “One” side must have unique values in the key column. If Power BI flips your relationship (Sheet2 >> Sheet1), it means the column in Sheet1 contains duplicates, so it cannot be the “One” side. To fix this, ensure the dimension table has distinct/unique keys (remove duplicates or create a DISTINCT table) and then create the relationship again.

[v-priyankata]

Hi @SurakshaKhurana 

Thank you for reaching out to the Microsoft Fabric Forum Community.

@Ankit_Rai @Kagiyama_yutaka @R1k91 @krishnakanth240  Thanks for the inputs.

I hope the information provided by users was helpful. If you still have questions, please don't hesitate to reach out to the community.

[v-priyankata]

Hi @SurakshaKhurana 

Hope everything’s going smoothly on your end. I wanted to check if the issue got sorted. if you have any other issues please reach community.

[krishnakanth240]

Hi @SurakshaKhurana 

Relationship direction is automatically determined based on which column has unique values and not how you try to set it. If it flips to many to one from Sheet 2 to Sheet 1 it means Sheet 2 has distinct keys while Sheet 1 contains duplicates. So workaround is to ensure one side has unique, non-blank values or creating a separate lookup table with distinct keys and relate both sheets to it.

[R1k91]

my advice is to study modeling basics. without basics you'll be in trouble working in power bi very soon.

[Kagiyama_yutaka]

I think the flip only means the Sheet1 key isn’t engine‑stable—tiny type‑drift or ghost‑dups—so cast that col once in PQ; if it still flips, make a small DISTINCT dim and hook both sheets to it.

[Ankit_Rai · Accepted solution]

Hello  @SurakshaKhurana 
This behavior is normal in Microsoft Power BI Desktop. Power BI automatically decides the relationship direction based on the data, so it may override what you select.

If it keeps switching from Sheet1 → Sheet2 to Sheet2 → Sheet1, it usually means Sheet1 does not have unique values in the column you’re using.

Instead of just checking duplicates, you can try this approach:

• Go to Power Query and check the count of distinct values in both tables
• Identify which table actually has unique keys
• Use that table as the “one” side of the relationship

  If Sheet1 is supposed to be the “one” side but contains duplicates, you can:

  • Create a new reference table with DISTINCT values, or
  • Clean the data to remove duplicates

    After that, recreate the relationship and it should work as expected.

[rohit1991 · Accepted solution]

Hii @SurakshaKhurana 

Power BI does not let you force a One-to-Many relationship manually it decides it based on data uniqueness. The table on the “One” side must have unique values in the key column. If Power BI flips your relationship (Sheet2 >> Sheet1), it means the column in Sheet1 contains duplicates, so it cannot be the “One” side. To fix this, ensure the dimension table has distinct/unique keys (remove duplicates or create a DISTINCT table) and then create the relationship again.