From: Carol Cheung <cacheung@consumercontact.com>
To: pgsql-sql@postgresql.org
Subject: Re: left outer join on more than 2 tables?
Date: Wed, 17 Jun 2009 09:07:23 -0400
Message-ID: <4A38EA8B.5000403@consumercontact.com> (raw)
In-Reply-To: <4A3826FB.8090907@gmail.com>
References: <4A3807CF.90109@consumercontact.com>
<396486430906161425i1cb7949enff5443cc2043805a@mail.gmail.com>
<4A38114B.7090106@gmail.com>
<396486430906161550v30befebelcfddd58ebc4b4f2d@mail.gmail.com>
<4A3826FB.8090907@gmail.com>
On 16/06/2009 19:12, Rob Sargent wrote the following:
> Richard Broersma wrote:
>> On Tue, Jun 16, 2009 at 2:40 PM, Rob Sargent<robjsargent@gmail.com>
>> wrote:
>>
>>
>>> Is there a city without a reference to region?
>>>
>>
>> I don't know, but the OP wanted to know complaints by region.
>>
>>
> I didn't try this, but with regionless cities, you may need a full join
> if you want a complete accounting of all complaints, some being logged
> to the null region.
>
>
>>
>>
>>
>>> And wouldn't you want to count(cm.id)?
>>>
>>
>> Count(cm.id) and Count(*) produce the same result. But I like
>> Count(*) more since it helps to correctly express the idea that we are
>> counting rows per group and not cm.id(s) per group.
>>
>>
>>
>>
>
> "Same result" is not true. I loaded tables.
> Using count(*) you get count=1 for regions without complaints. Using
> count(complaint.id) you get count = 0. (The deference amount to
> counting the left hand side (region) vs the right hand side (complaint)
> which I believe is what OP is after).
>
Thanks everyone for your help. Your solutions worked. Much appreciated.
- Carol
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To: pgsql-sql@postgresql.org
Cc: cacheung@consumercontact.com
Subject: Re: left outer join on more than 2 tables?
In-Reply-To: <4A38EA8B.5000403@consumercontact.com>
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