Submitted by: @dyemanov

Historically, non-null DB_KEY was returned for VMS external tables as they could be indexed and also updated and deleted, so direct positioning was a requirement. For other external tables it was always a zero quad word. I don't consider it being a major problem, however it doesn't look absolutely correct:

create table t external file 'c:\ext.bin' (col int);
insert into t (col) values (1);
insert into t (col) values (2);
insert into t (col) values (3);

execute block returns (val int)
as
declare dbkey char(8) character set octets;
begin
select first 1 rdb$db_key from t into :dbkey;

for select col from t where rdb$db\_key = dbkey into :val do
  suspend;

end

This query returns you the whole table instead of the expected first row only. I don't think it would hurt anyone if we'd return a proper DB_KEY for external tables, just for the consistency sake. It could be either a monotonically increasing row number or an offset inside the external file.

Commits: 11495a5