From: gurkan@resolution.com
To: pgsql-sql@postgresql.org
Subject: Re: converting Informix outer to Postgres
Message-ID: <1162943346.45511b720c367@www.resolution.com>
Date: Tue, 07 Nov 2006 18:49:06 -0500 (EST)
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 8bit
User-Agent: IMP/PHP IMAP webmail program 2.2.8

> --- gurkan@resolution.com wrote:
> 
> > Hi all,
> > I have been working on this Informix SQL query which has an outer
> join.
> > I have attached Informix query and my "supposedly" solution to this
> query
> > but I cannot get the same count. I appreciate for any help.
> > Thanks.
> > 
> > --Informix query
> > select count(u.id)
> > from user u, invention i, inv_contracts ic, inv_milestones im1,
> milestonedef mdef1,
> > OUTER inv_milestones im2,
> > milestonedef mdef2
> > where u.id = i.user_id and
> > ic.inv_id = i.id and
> > ic.contract_id = mdef1.contract_id and
> > im1.inv_id = i.id and
> > mdef1.id = im1.milestone_id and
> > im1.datesent BETWEEN '2005-05-05' AND '2005-05-10' and
> > ic.contract_id = mdef2.contract_id and
> > im2.inv_id = i.id and
> > mdef2.id = im2.milestone_id and
> > im1.datereceived IS NULL
> > 
> > --Postges query
> > select count(u.id)
> > from dbuser u, inv_contracts ic, inv_milestones im1, milestonedef
> mdef1,
> > --OUTER inv_milestones im2,
> > milestonedef mdef2 LEFT OUTER JOIN inv_milestones im2 ON mdef2.id =
> im2.milestone_id
> > LEFT OUTER JOIN invention i ON im2.inv_id = i.id
> > where u.id = i.user_id and 
> > ic.inv_id = i.id and 
> > ic.contract_id = mdef1.contract_id and 
> > im1.inv_id = i.id and 
> > mdef1.id = im1.milestone_id and 
> > im1.datesent BETWEEN '2005-05-05' AND '2005-05-10' and
> > ic.contract_id = mdef2.contract_id and
> > --im2.inv_id = i.id and --QUERY1
> > --mdef2.id = im2.milestone_id and --QUERY2
> > im1.datereceived IS NULL
> 
> Is there a reason that these two lines are commented out in the
> postgresql query?
The reason is that once it is converted to postgres (LEFT OUTER), those two query 
moved into LEFT OUTER JOIN clause.

For simplicity;
if the Informix query were as;

select count(u.id)
from user u, 
OUTER inv_milestones im2,
milestonedef mdef2
where 
mdef2.id = im2.milestone_id --QUERY2

in Postgres it would have been as;

select count(u.id)
from dbuser u, 
--OUTER inv_milestones im2,
milestonedef mdef2 LEFT OUTER JOIN inv_milestones im2 ON mdef2.id = im2.milestone_id
--where  
--mdef2.id = im2.milestone_id --QUERY2

In original Informix outer query has one OUTER but has two
queries(QUERY1,QUERY2). I can test
my conversion at one query a time meaning I can do my conversion if there were
only QUERY1 
or QUERY2. In my test cases they return the same number on count, but I cannot do it
for QUERY1 and QUERY2 at the same time. I have done it before for this kind of
query but
for this case my solution is not working.
thanks for help.

-------------------------------------------------
This mail sent through IMP: www.resolution.com