DAX for Summarizing at an aggregate level

[Anonymous]

I have two tables. One with the total sale amount for the month by car and another with the details showing car, model, and sales person. I have merged the to tables together and need to find a way to write dax that gives me the sum of the amount sold without over counting. **NOTE in my example I do not have the ability to split these tables out into two tables and relate them so I need a DAX that can work off the belnded fact table (Table 3).

I need a DAX measure that sums the amount for cars sold. In table 1 below the total amount that was sold was $2400. (1000 + 200 + 400 + 800). You can see on the green merged table 2 below those amount values are duplicated and I need to be able to sum the column, but sum the unique values by car.

Sales Amount for the month by Car (Table 1)

Sales Detail (Table 2)

Table 3: Blended Fact Table (Main Fact Table I need DAX built off of)

Here is the formula I have showing the "INCORRECT" value....

Sales Amount:=SUM(Table3[Amount])

7,200 is not the right amount, it should be 2,400 for the month.

I need a dax formula that shows me this....

How do you write dax off Table 3 that gives you the table above showing 2,400, if the amount values from the first table are duplicated when merged with the second table?

[Anonymous]

Yep that worked! Curious if there is another way to write the formula without the Average? Could you leverage SUMMARIZE somehow?

[Greg_Deckler]

@Anonymous Well, there are a couple ways of going about it but that way was the simplest for your scenario. SUMMARIZE can get you in trouble sometimes.

[Greg_Deckler · Accepted solution]

@Anonymous First, please vote for this idea: https://ideas.powerbi.com/ideas/idea/?ideaid=082203f1-594f-4ba7-ac87-bb91096c742e

Try: 

Measure 2 = 
    VAR __Table = GROUPBY('Table5',[Car],"__Avg",AVERAGEX(CURRENTGROUP(),[Amount]))
    VAR __Result = SUMX(__Table,[__Avg])
RETURN
    __Result

This looks like a measure totals problem. Very common. See my post about it here: https://community.powerbi.com/t5/DAX-Commands-and-Tips/Dealing-with-Measure-Totals/td-p/63376

Also, this Quick Measure, Measure Totals, The Final Word should get you what you need:
https://community.powerbi.com/t5/Quick-Measures-Gallery/Measure-Totals-The-Final-Word/m-p/547907

Also: https://youtu.be/uXRriTN0cfY
And: https://youtu.be/n4TYhF2ARe8