Question about using the UNLOAD statement

Hi,

I have a relatively large database I need to rebuild from scratch.   I can't use the dbunload utility because the database is corrupt, so I have to go table by table.

I also thought that since I have to do this, that I should take this oportunity to trim the database and copy only relevant data.   So I thought about using the UNLOAD statement to export a subset of the data.

For example, the table "iTrans":

UNLOAD SELECT * FROM iTrans  WHERE TransDate >= '2014-01-01' TO '\\transfer\itrans.dat";

This works perfect.   The problem is with "iTrans" child table "iTransRow".   The primary key is a two column key (IdLoc, IdSeq).   

HOW do I filter the rows in "iTransRow" to only contain those that are in the "iTrans" subset?   If the the primary key was a single column it would be easy using the IN clause, but with a two column key?

I came up with this, but I think I'm pretty sure there must be a better way...

UNLOAD SELECT * FROM iTransRow

WHERE 

EXISTS (SELECT * FROM iTrans AS A WHERE A.Fecha >= '2014-01-01' AND iTransRow.IdLoc=A.IdLoc AND iTransRow.IdSeq=A.IdSeq)

TO '\\transfer\itransrow.dat'

These are fairly large tables, and I need to rebuild this asap

Thanks for any ideas,

Edgard