Re: Outer Join with an extra condition

dn.perl_at_gmail.com wrote:
> I am taking a left outer join to which I would like to add a
> condition.
>
> create table tmp_nani_student(stid number) ;
>
> insert into tmp_nani_student values(1) ;
> insert into tmp_nani_student values(2) ;
> insert into tmp_nani_student values(3) ;
> insert into tmp_nani_student values(4) ;
>
>
> create table tmp_nani_marks(stid number, marks number, grade number) ;
>
> insert into tmp_nani_marks values(1, 51, 3) ;
> insert into tmp_nani_marks values(2, 71, 2) ;
> insert into tmp_nani_marks values(4, 81, 1) ;
> insert into tmp_nani_marks values(5, 55, 3) ;
> commit ;
>
> Then I run :
> select a.stid, b.marks, b.grade
> from tmp_nani_student a, tmp_nani_marks b
> where a.stid = b.stid (+) and (b.grade < 3 or not exists (select
> c.stid from tmp_nani_marks c where a.stid = c.stid) )
>
> So far so good.
>
> But then I add one more row to the second table:
> insert into tmp_nani_marks values(2, 17, null) ;
>
> Now I want to run a query which would exclude this new row where
> grade=null. If the outer join fetches rows with grade=null, that is
> fine. But I don't want to fetch records where grade is explicitly set
> to null.
>
> Run again:
> select a.stid, b.marks, b.grade
> from tmp_nani_student a, tmp_nani_marks b
> where a.stid = b.stid (+) and (b.grade < 3 or not exists (select
> c.stid from tmp_nani_marks c where a.stid = c.stid) )
>
> But the record (2,17, null) shows up. I don't want it to show up. What
> would be the query for it?
>
> TIA.
AND <column_name> IS NOT NULL;

-- 
Daniel A. Morgan
Oracle Ace Director & Instructor
University of Washington
damorgan_at_x.washington.edu (replace x with u to respond)
Puget Sound Oracle Users Group
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