subtract between two columns from 2 different tables

[game1]

Hi,
I want to subtract between two columns from 2 different tables.
For example, I have TABLE1[DateBirth] and TABLE2[DateDeparture]. The problem is that there is no cardinality between TABLE1 and TABLE2. How should I go about doing this? Related does not work and when I use datediff, I do not have access to the fields of TABLE2, because I created "DiffDate = " in TABLE1

[ChielFaber]

Are there any columns in your datascource that could be used to create a key? Could you provide a sample table with dummy data for us to provide a solution?

[game1]

Yes. Both table have in common IDName. But I try to connect cardinality and it didn't work.