From: Axel Rau <Axel.Rau@Chaos1.DE>
To: Richard Huxton <dev@archonet.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Selecting count of details along with details columns
Date: Thu, 29 Sep 2005 21:08:15 +0200
Message-ID: <409f1e679d5f8744e1609d5c447d5f15@Chaos1.DE> (raw)
In-Reply-To: <433BBC07.5040208@archonet.com>
References: <8365994213849c93946e61ded7d12318@Chaos1.DE>
<433BA637.7040106@archonet.com>
<a79cd5e3132c2d4c3430a34e64d93ebe@Chaos1.DE>
<433BBC07.5040208@archonet.com>
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Am 29.09.2005 um 12:03 schrieb Richard Huxton:
> Axel Rau wrote:
>> Am 29.09.2005 um 10:30 schrieb Richard Huxton:
>>> Axel Rau wrote:
>>>
>>>>
...
> Ah - this is two questions:
> 1. What are the unique (t2_name,t1_name) pairings?
> 2. How many different (t1.id) values are there for each t2.
>
> So - something like:
>
> SELECT names.T2_name, names.T1_name, counts.num_t2
> FROM
> (
> SELECT DISTINCT T2.T2_name, T1.T1_name
> FROM T2,T1
> WHERE T2.id = T1.fk_t2
> ) AS names,
> (
> SELECT T2.T2_name, COUNT(T1.id) AS num_t2
> FROM T2, T1
> WHERE T2.id = T1.fk_t2
> GROUP BY T2.T2_name
> HAVING COUNT(T1.id) > 1
> ) AS counts
> WHERE
> names.T2_name = counts.T2_name
> ;
>
> You could write the "names" sub-query with a GROUP BY if you wanted of
> course.
Exactly, that query works as I expected. Thank you.
Can you answer this question as well:
> Looking for a workaround, I learned that aggregate functions are not
> allowed in WHERE clauses.
> Question: Is this conform with the standard?
Axel
Axel Rau, Frankfurt, Germany +49-69-951418-0
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To: pgsql-sql@postgresql.org
Cc: Axel.Rau@Chaos1.DE, dev@archonet.com
Subject: Re: Selecting count of details along with details columns
In-Reply-To: <409f1e679d5f8744e1609d5c447d5f15@Chaos1.DE>
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