Previous Month showing same value as Current Month

[remi113]

Hello everyone, I am trying to make a graphic (cards) comparing current month sales to previous month sales.  I am using a month-year sales table and a calendar table.  For some reason, I can not get it right.  Both values are always the same, no matter what month I select.  I am unsure if it is my DAX function or modeling schema, however I have tried every possibility of cardinality and cross filtering between the tables, and nothing fixes it.  I am using EDATE, but have also used DATEADD I think it was and a couple others.

I will upload an image that explains, the DAX function I am using is: 

PREVIOUSMONTH = CALCULATE(SUM('month-year sales'[monthly sales]),EDATE('Calender Table'[Date],-1))

Whenever I try to remove SUM, it gives me error: "A single value for column 'monthly sales' in table 'month-year sales' cannot be determined. This can happen when a measure formula refers to a column that contains many values without specifying an aggregation such as min, max, count, or sum to get a single result."

Thank you.

[FreemanZ]

hi @remi113 

could you make a screenshot of the month-year sales table?

[HassanAshas]

Please show the complete Data Model. 

With what do you have the bidirectional relationship with your Month-Year Sales Table? 

And talking of Month-Year Sales Table, what is the reasoning behind creating this table? I think you have created an additional table which was never required at first place, and hence made your Data Model complex. 

As for the DAX, I would suggest using PREVIOUSMONTH to get the values for your last month, 

PREVIOUSMONTH = CALCULATE(SUM('month-year sales'[monthly sales]), PREVIOUSMONTH('Calendar Table'[Date]))

[remi113]

Hi, I will attach an image of my data model.  I honestly am not sure why I created a separate table, I just knew I needed this data so created it in Excel and imported it, I am new to PowerBI and modeling, this is my first project.  When I use PREVIOUSMONTH, the DAX accepts it, but returns (Blank) for every month in PREVIOUSMONTH.  Here is my data model.