In the target table, create a calculation field, type text, as
List ( field1 ; field2 )
and use that as the match field.
Wow thanks, cool, worked. Forgot LIST ;->
Forgot LIST ;->
You don't have to use List() – the result just has to be a list, and that's easiest with that function, rather than, say …
field1 & Case ( not IsEmpty ( field1 ) and not IsEmpty ( field2 ) ; ¶ ) & field2