Re: Subselects open issue Nr. 5

> 5. I need in advice: if subquery introduced with NOT IN doesn't return
>    any tuples then qualification is failed, yes ?

Informix treats the subselect as NULL if no rows are returned.
Therefore all parent rows that are not null are returned.

select * from taba where a not in (<a select returning no row>);    --
is same as
select * from taba where a is not null;

Andreas