Tried to merge and used the condition afterwards. It seemed to work,
thank you.
However the section 2) below raised another question. I have several
observations per id in both files, does it matter?
If you have a many-to-many merge (ID not unique in either master or
using file) read the manual description of many-to-many merges and
the problems they involve. It is tricky to deal with that sort of thing.
