Re: LEFT JOIN ...

On Mon, 18 Jun 2001, Tom Lane wrote:

> The Hermit Hacker <scrappy@hub.org> writes:
> >       FROM note_links nl, notes n LEFT JOIN calendar c ON (n.nid = c.nid)
> >       WHERE (n.type = 'A' OR n.type = 'N' OR n.type = 'H' OR n.type = 'C')
> >             AND (nl.id = 15748 AND contact_lvl = 'company')
> >             AND n.nid = nl.nid
> >       ORDER BY start DESC;
>
> > Is there some way to write the above so that it evaluates:
> > first, so that it only has to do the LEFT JOIN on the *one* n.nid that is
> > returned, instead of the 86736 that are in the table?
>
> Try adding ... AND n.nid = 15748 ...  to the WHERE.  It's not very
> bright about making that sort of transitive-equality deduction for
> itself...

n.nid is the note id ... nl.id is the contact id ...

I'm trying to pull out all notes for the company with an id of 15748:

sepick=# select * from note_links where id = 15748; nid  |  id   | contact_lvl | owner
-------+-------+-------------+-------84691 | 15748 | company     | f
(1 row)