Remove duplicates from union

Hello 

I'm doing custom table with select columns in dax calculations and when creating relationship sales, products , order gives me many-many options , so how can i check and remove duplicates from custom table. so relationship will many to one between fact & custom dim.

Table = 

Var _Sales = selectcolumns(Actuals,"ID", ]Activity_Id],"Name", ]Activity_Name])

Var _Products = selectcolumns(Actuals,"ID", ]Activity_Id],"Name", ]Activity_Name])

Var _Orders = selectcolumns(Actuals,"ID", ]Activity_Id],"Name", ]Activity_Name])

Var _Vunion = distinct (union( _Sales, _Products,_Orders)

return  _Vunion 

thanks

vs