Creating relationship between two tables using null calculated columns SSAS

[KaiRado]

Hi!

I'm having a problem of recreating a solution that my previous colleage did and nobody has no idea what the solution really means.
There are two tables in tabular model: a dimension (D) and a fact table (F) which have the same source but each table contains different number of attributes. Each table contains a calculated column "Link" which has no expression:

These two tables has a relationship (Many to one, Both Directions) using these two calculated columns:

How does it even work?

Even though I don't understand the logic, I tried to recreate this solution using another two tables, but I'm getting an error: Link column contains a duplicate value null and this is not allowed for columns on the one side of a many-to-one relationship or for columns that are used as the primary key of a table. 

Can somebody please explain what is going on and why am I getting an error while trying to recreate almost the same thing that actually works?

Thank you in advance!

[v-yueyunzh-msft · Accepted solution]

Hi , @KaiRado 

According to the error message you encountered, you are encountering a problem about data modeling, you have created a many-to-one relationship for two tables in the data model, the link column in dimension table (D) is used as one end column, but the link' column contains duplicate null values, there are two solutions to this error:

The first is to go to Power Query and use filtering to filter out rows in the link column that contain null values and reload them into Power BI

The second is to reconstruct the relationship between the two tables and respecify the primary key associated between the two tables, because as far as I know, if the related primary key between the two tables also contains a null value, it does

It has a certain impact and trouble on data screening and display.

Best Regards,

Aniya Zhang

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