> > First you said you were using isql; next, you said you were using
> an interactive statement processor. Which is it?
>
> But isn't ISQL "Interative SQL" ? Isn't Mitec IB Query an interactive
> ISQL editor ?

No, isql is isql, Mitec is Mitec, iboconsole is iboconsole, etc.
See the pattern ? :-)

> --- added by me
> SET TERM !!;
> --- added by me
> CREATE TRIGGER my_before_trigger FOR my_table
> BEFORE INSERT
> AS
> BEGIN
> IF (NEW.my_number IS NULL)
> THEN NEW.my_number = GEN_ID(my_generator, 1);
> END
> --- added by me
> SET TERM ; !!
> --- added by me

You forgot to put terminator after the Create Trigger command, i.e.
...

> THEN NEW.my_number = GEN_ID(my_generator, 1);
> END !!
> SET TERM ; !!

Ivan