Can one use a define field for a JOIN statement?
It's actually not as simple as that... here's what I mean.

DATABASE A:
-----------
CONTRACT A8
ITEMDESC A15
QTY I5

DATABASE B:
-----------
CONTKEY A11
DELVADDR1 A20
DELVADDR2 A20

DEFINE FILE B
CONTKEY8/A8 EDIT(CONTKEY,'99999999$$$');

I want to join A and B via CONTRACT and CONTKEY because the first 8 chars of CONTKEY is the contract.
When I executed the join after the DEFINE stmt, I got...
(FOC370) THE FIELDNAME USED IN JOIN CANNOT BE FOUND IN THE FILE

Thanks in advance for any help!

JOIN CONTKEY8 WITH CONTKEY ...

Should do the job.

The with tells you where the define is located within a multi segment structure although this should not be strictly necessary since wf can tell where a define field is logically related unless it is a constant.

Don't forget that that contrary to intuition, the DEFINE goes after the JOIN.

And the JOIN goes before the DEFINE. This is a well-documented feature. Look for define-based joins.

Some databases allow the join to the first part of a key without having to do a define. Can't tell what DB you are using, though.

One other note - with your defined field you would have to join B to A. Joining A to B would not work. You can't join a real field in A TO a defined field in B, but you can join FROM a defined field in B to a real field in A.

What would be the result if you change the USAGE value of this field in the master?
If the real value in the Database B should be A8 then that would be an other solution. (In fact a correction on the database design)