Powerbi Relationship

[BlessingNtshele]

I have 2 fact tables( Cluster Targets and Recharge Data) and two dimensions( Calender and Dim Location), I have connected my two fact table to the dim location table. But when I am connecting to the calender table the relationship doesn't wanna be active. Please assist what should I do

[halfglassdarkly · Accepted solution]

PowerBI won't let you add a second active Many-to-Many relationship to a table that already has one.

I'd start by looking at whether you need all those Many-to-Many relationships though. If your Dim Location table is actually functioning as a dimension table then your primary key should be unique and at least one of the relationships for that table should be able to be changed to one-to-many. If you can change to 'Dim Location' 1------>* '2023 Cluster Targets' then you should be able to make 'Calender' *------>* '2023 Cluster Targets' active.

If you're using month and not date as your key you could also consider whether to add a new Month dimension to use as a bridging table between your Calender dim and other tables filtered by month.

[BA_Pete · Accepted solution]

Hi @BlessingNtshele ,

I broadly agree with @halfglassdarkly , but I would go further and say that you should not be using Many:Many relationships AT ALL.

Aside from some niche use-cases, if you're modelling using M:M relations in general, you're modelling wrong.

This isn't just a 'looks pretty' thing, this is a 'will cause you serious problems down the line' thing (your post is case-in-point).

For example: Your Calendar to Cluster Targets relation should absolutely be One:Many. You would implement this correctly by creating a proper date column within your Cluster Targets table. How you go about this depends on the actual format of your Cluster Targets[Month] column but, for the sake of example, let's assume it's Text data type in YearMonth format, like this: "202305".

In Power Query, you would convert this into a proper date something like this:

#date(
    Text.Start([Month], 4),
    Text.End([Month], 2),
    01
)

You would then be able to create a proper One:Many relation one Calendar[Date] : Cluster Targets[NewDateColumn].

You should be looking to implement similar fixes with all of your tables that must relate to a dimension table before modeling.

Pete

[halfglassdarkly · Accepted solution]

PowerBI won't let you add a second active Many-to-Many relationship to a table that already has one.

I'd start by looking at whether you need all those Many-to-Many relationships though. If your Dim Location table is actually functioning as a dimension table then your primary key should be unique and at least one of the relationships for that table should be able to be changed to one-to-many. If you can change to 'Dim Location' 1------>* '2023 Cluster Targets' then you should be able to make 'Calender' *------>* '2023 Cluster Targets' active.

If you're using month and not date as your key you could also consider whether to add a new Month dimension to use as a bridging table between your Calender dim and other tables filtered by month.