left outer join using dax, Multiple to Multiple

[mim]

I have two tables in my data model, currently,  i am exporting them to Excel do the merge there using PQ and import back to PowerBI Data model, as you would imagine, this is not efficient.

i have read about the new " naturalleftoutjoin ", i can't make it to works, if I add the common id, it complains that there is a duplicate columns, if i remove it, it say there is no common column, clearly i don't understand how it works.

so here is my scenario; notice the id is duplicated in both tables and it is by design, so any idea how to create the calculated table Result using DAX ?

[TomMartens · Accepted solution]

Just playing around with CROSSJOIN and UNION as well and maybe a GENERATE using the nonexisting and ROW to provide space for the BLANK value 🙂 but now I have to take some sleep

[OwenAuger · Accepted solution]

Using DAX you can do something like this, but M is probably preferable.

Result =
GENERATEALL (
    'Table 1',
    VAR Table1ID = 'Table 1'[id]
    RETURN
        SELECTCOLUMNS (
            CALCULATETABLE ( 'Table 2', 'Table 2'[id] = Table1ID ),
            "price", 'Table 2'[price]
        )
)

[mim]

I need to do it in DAX using calculated table, not PowerQuery, the reason is table 1 and table 2 are already loaded in the Data model using some heavy PowerQery Transformation, which take nearly 20 minutes, 

ideally if PQ supported loading table from existing data model, it would have been great, but that's not the case now, I thought it can be possible using DAX.

[TomMartens]

Silly me, sorry for bothering ...

The DAX functions NATURALLEFTOUTERJOIN() requires an relationship between the tables (one to many), seems a little strange, but thats how the function currently works.

And you can't create a relationship in dax because none of the two columns is unique.

[mim]

@TomMartens thanks Tom, I thought maybe crossjoin with filter on a common id, plus union where the id do not match may do the tricks !!! 

[TomMartens · Accepted solution]

Just playing around with CROSSJOIN and UNION as well and maybe a GENERATE using the nonexisting and ROW to provide space for the BLANK value 🙂 but now I have to take some sleep