I am trying to execute this query:

UPDATE SCHED S SET S."Print Order" = (SELECT COALESCE("Print Order",0) FROM SERVICE V WHERE V.ID = S."Serv ID") 

But I get this error:

Context: Statement::Execute( UPDATE SCHED S SET S."Print Order" = (SELECT COALESCE("Print Order",0) FROM SERVICE V WHERE V.ID = S."Serv ID") )

Message: isc_dsql_execute2 failed

SQL Message : -625

The insert failed because a column definition includes validation constraints.

So clearly "Print Order" in the SERVICE table has gotten to be a null somehow.  So to find this and fix it, I do this query:

SELECT a."Print Order", a."Description" FROM service a where a."Print Order" is null

But no rows are returned.  How can that be?

  I am running on Windows XP and FlameRobin reports the server version to be WI-V2.0.1.12866 Firebird 2.0.

What am I overlooking here?