Power BI Desktop Many to Many Relationships

[berta2b]

Hi there guys, have an issue with typical many-to-many relationships in Power BI desktop.

Here's my scenario:

Bookings (30 columns)        BookingsLink                       BookingsEMails (20 columns)
========                       ============            ==============
Booking Reference               Booking Reference              Booking Reference
BookingDate                       EMail Sent
Brand                                  EMail Address
Amount
Customer First Name
Customer Last Name
Etc . . .

So Bookings & BookingsEMails tables have multiple rows for the same Booking Reference, hence the DISTINCT Booking Reference BookingsLINK table is required to JOIN Bookings to BookingsEMails.

The relationships exist between Bookings -> BookingsLink and BookingsEMails -> BookingsLink on Booking Reference (Many to One)

So I can create a tabular report selecting BookingsLink.BookingReference and then Bookings.BookingDate, Bookings.Brand and Bookings.Amount, and the same against BookingEMails, selecting BookingsLink.BookingReference and then BookingsEMails.EMailSent.

This is fine, but when I try and create a report using for example BookingsLink.BookingReference, BookingDate AND THEN BookingsEMails.EMailSent I get the 'Can't determine relationships between the fields' error although the many-to-many relationships exist.

I have many columns on Bookings and BookingsEMails that I want to report together on the same tabular report.

Please can you help!

Many Thanks.

[v-shex-msft]

HI @berta2b,

Power bi not support many to many relationship, you need to use table which has the unique key to link to those tables.

For example:

Table(Many)    ——>     Table(one)     <——      Table(Many)

                   (Many to one)               (one to many)

BTW, multiple blank records also will identified as the duplicate records, if your unique table contains them, you should remove them before create relationship.

Regards,

Xiaoxin Sheng

[KarenSofia62]

How to put dynamic role level security on this case?

[berta2b]

Hi Xiaoxin, thanks so much for your reply.

I have created this unique table, BookingsLink which has unique keys allowing the Many to one, One to Many between the two other tables.

My problem is although this relationship has been setup within Power BI Desktop 'Relationships' where I would think would resolve this, I can't access columns from the Table(Many) tables in one tabular visualisation report.

There are no blank keys, the Link table contains just the unique keys and no blanks.

Thanks again.

Bert

[v-shex-msft]

Hi @berta2b,

Did you check the 'cross filter direction' option at relationship setting? If it has setting to 'single', the relationship only works on one side, you can modify it to 'both' to work through it.

Regards,

Xiaoxin Sheng

[berta2b]

Sorry I have to apologise, I have confused the issue somewhat, when I copied and pasted the tables structures the columns moved around a bit!

Here is the correct design.

Bookings (30 columns)        BookingsLink                       BookingsEMails (20 columns)
========                       ============            ==============
Booking Reference               Booking Reference              Booking Reference
BookingDate                                                                  EMail Sent
Brand                                 
Amount
Customer First Name
Customer Last Name
Etc . . .

[berta2b]

Hi Xiaoxin, here's the correct design again

Bookings (30 columns)        BookingsLink                       BookingsEMails (20 columns)
========                       ============            ==============
Booking Reference               Booking Reference              Booking Reference
BookingDate                        (UNIQUE)                           EMail Sent
Brand                                                                             EMail Address
Amount
Customer First Name
Customer Last Name
Etc . . .

So the BookingsLink table has only one columns 'Booking Reference' which is unique and I'm trying to select 'Booking Date' and 'EMail Sent' for the same tabular report and then the issue.

Thanks and sorry for the confusion again.

Bert

[berta2b]

Hey Xiaoxin, just seen your post to check the bi-directional option.

I'll give this a try and get back to you.

Many Thanks.

Bert

[berta2b]

Hi Xiaoxin, I tried your suggestion but this didn't work I'm afraid 😞

I set the 'Cross Filter direction' to BOTH on my 'Many to One' relation 'Bookings' -> 'BookingsLink' and 'BookingEMails' -> 'BookingsLink' and still had the same issue.

Bert

[v-shex-msft]

Hi @berta2b,

>>I set the 'Cross Filter direction' to BOTH on my 'Many to One' relation 'Bookings' -> 'BookingsLink' and 'BookingEMails' -> 'BookingsLink' and still had the same issue.

Can you provide the sample file to test? It is hard to troubleshooting without sample file.

Regards,

Xiaoxin Sheng

[berta2b]

Hi Xiaoxin, I'm preparing this for you now.

Many Thanks

Bert

[berta2b]

Hey Xiaoxin, I have the sample file prepared for you. How can I get this sent as I can't add attachments to this message?

Many Thanks.

Bert

[v-shex-msft]

Hi @berta2b,

You can upload it to onedrive and paste the link here.

Regards,

Xiaoxin Sheng

[berta2b]

Hi Xiaoxin, will load to OneDrive location and send link.

Before I do, the file will be password encrypted so how can I best send this password to you?

Thanks

Bert

[v-shex-msft]

Hi @berta2b,

This is fine, but when I try and create a report using for example BookingsLink.BookingReference, BookingDate AND THEN BookingsEMails.EMailSent I get the 'Can't determine relationships between the fields' error although the many-to-many relationships exist.

As you mentioned, if you use the unique table key to link column which contains in multiple side, it will be works normal?

If this is a case, It seems like power bi not support direct mapping the multiple records to multiple records.

I'd like to suggest you use the unique key as the route to mapping those records.

Regards,

Xiaoxin Sheng

[berta2b · Accepted solution]

Hi Xiaoxin, sorry for not getting back to you earlier.

Yes that is the case, the two outer tables have multiple records and not single entries so I agree Power BI won't support this.

I've remodelled the data tables to insteadof trying to have multiple records in a many-to-many relationship that all the columns from these tables are added to one table which is a work around.

Many Thanks Xiaoxin for all your help with this issue.

Regards

Bert.