Imagine two simple tables - one with IDs and the other with urls. Each url contains one ID, the ID position in the url is not fixed, and urls might also contain other non-ID numbers as the last example in Table2. Simple Left(), SubField(), KeepChar() won't work.
I tried to extract the IDs from the urls with If(IsNum(url_sub) and Len(url_sub) = 4, url_sub, Null()) which somehow works as an expression but not in the script. Probably Mapping and MapSubString() is the best option but I couldn't make it work either. Do you have any ideas?