Combining two tables into one graphic

I have two different tables. Both have the variable "Day of Week". I want my x-axis to be categorical: Day of Week. I want one variable from one table and one from the other as my values. Can I do this?

I am in direct query so my DAX is very limited (and we want high performance, so we do not want to override that) and I cannot create any new tables in order to link things together. Also neither of my "Day of Week" columns has unique values, so I cannot make a relationship between them (even though they are the same variable). 

Any ideas how I can achieve this? 

Thanks in advance.