Problem with union (selectcolumns

[U156531]

Tablemeasure = Union(
selectcolumns(Table A,"Opening_Date", Table A[Opening_Date]), 
selectcolumns(Table B,"Business_Date", Table B[Business_Date]), 
)

I created a measure using this format above but when I try to put it into a visual I get the error below. Anyone have an idea of what I might be doing wrong?

[AmiraBedh · Accepted solution]

If you need a list of dates for a visual, create a calculated table instead of a measure :

CombinedDatesTable = UNION(
    SELECTCOLUMNS(TableA, "Date", TableA[Opening_Date]),
    SELECTCOLUMNS(TableB, "Date", TableB[Business_Date])
)

then for the measure : 

UniqueDateCount = DISTINCTCOUNT(UNION(SELECTCOLUMNS(TableA, "Date", TableA[Opening_Date]), SELECTCOLUMNS(TableB, "Date", TableB[Business_Date])))

[U156531]

This is what I created but I'm only getting the Material column in the resulting table?

TableUnion = union(selectcolumns('material class',"Material", [Material Class]),selectcolumns('merge1',"Quantity", [Quantity Received for Current Year]), selectcolumns('material_class' ,"Material", [MATERIAL CLASS]  ) ,  selectcolumns('RFID/Barcode Defective Material Submittals' ,"Quantity", [quantity]  ) )

[AmiraBedh]

Can you please share your pbix file ?

[U156531]

Your solution worked, I just had to tweek it a bit for my situation. I accepted your solution.