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Re: left outer join on more than 2 tables? (UNCLASSIFIED)

From: "Hall, Crystal M CTR DISA JITC" <Crystal(dot)Hall(dot)ctr(at)disa(dot)mil>
To: <pgsql-sql(at)postgresql(dot)org>
Subject: Re: left outer join on more than 2 tables? (UNCLASSIFIED)
Date: 2009-06-16 21:52:14
Message-ID: 00E9117C300386479B7E2F3CDBF798F605534293@pothia.disanet.disa-u.mil (view raw or flat)
Thread:
Lists: pgsql-sql
Classification:  UNCLASSIFIED 
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Maybe I am way of base here, but I see a reference to region in this
query.  However, I think count(cm.id) is correct because some would have
a count of 0.  Count(*) would produce counts when there are no
complaints. (If I understand the logic, again, I am VERY new to this) 

-----Original Message-----
From: pgsql-sql-owner(at)postgresql(dot)org
[mailto:pgsql-sql-owner(at)postgresql(dot)org] On Behalf Of Rob Sargent
Sent: Tuesday, June 16, 2009 2:40 PM
To: pgsql-sql(at)postgresql(dot)org
Subject: Re: [SQL] left outer join on more than 2 tables?

Richard Broersma wrote:
> On Tue, Jun 16, 2009 at 1:59 PM, Carol 
> Cheung<cacheung(at)consumercontact(dot)com> wrote:
>   
>> I would like to find the counts of complaints by region and I would 
>> like all regions to be displayed, regardless of whether or not 
>> complaints exist for that region. Is left outer join what I'm looking
for?
>>     
>
>    SELECT R.region_name, Count(*) AS RegionComplaints
>      FROM Region AS R
> LEFT JOIN City AS Ci
>        ON R.id = C.region_id
> LEFT JOIN Complaint AS Cm
>        ON Ci.id = Cm.city_id
>  GROUP BY R.region_name;
>
>
>   
Is there a city without a reference to region?  And wouldn't you want to
count(cm.id)?

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Next:From: Richard BroersmaDate: 2009-06-16 22:45:03
Subject: Re: left outer join on more than 2 tables?
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Subject: Re: left outer join on more than 2 tables?

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