Calculate the number of Distinct subject - joining data from 3 tables

[keivan]

Hi all,

I would like to calculate the number of distinct Subject.
My dataset is compose in this way:

Calendar Table (Date, Year, Month, etc.)
Subject Table (Subject_id, Name, Surname, etc.)
Connections Table (Subject_id, Connection_id, etc.)
Fetches Table (Fetch_id, Connection_id, Flag_error, etc.)

On SQL I would do

SELECT DISTINCT subject_id
FROM subjects s

inner join connections c on c.subject_id = s.subject_id
inner join fetches f on f.connection_id = c.connection_id

where f.flag_error = 0

Infact I want to calculate distinct subject (where subject_id are store on the subjects table) and I need to join with the fetches table, however there is not a direct key from fetches table and subject table, so I need the connection table as a bridge.

Furthermore I want to calculate only the subject where the donwload of the data (fetch) is not an error (flag_error = 0)

Sorry to bother you, but I don't know how to join multiple table as a variable in BI 
Thanks,

[djurecicK2]

Hi @keivan ,

 You can join tables in Power BI, but many times relating tables is a better option.

Here is some additional information:

https://learn.microsoft.com/en-us/power-bi/transform-model/desktop-create-and-manage-relationships

https://radacad.com/combine-tables-or-create-relationships-the-power-bi-modeling-best-practice

[keivan · Accepted solution]

PSU= Calculate(DISTINCTCOUNT( subjects[subject_business_id]), FILTER ('fetches', fetches[flag_error] = 0))

I didn't realize that having a relationship I didn't need to join and I was already able to perform cross filter