How to show items from a different table when value in table is blank?

I have 3 tables, an ID table with 2 different spend tables. The ID table has a 1-to-many relationship with both spend tables. When putting this into a matrix, there is a column that shows blank and has spend in that column. This is because one of the spend tables has more ID's than the ID table. Is there a way that I could create a calculated column or something else to say if ID is blank in that relationship, show the ID's from the spend table?