Re: Syntax bug? Group by?

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: Mark Woodward <pgsql(at)mohawksoft(dot)com>
Cc: Shane Ambler <pgsql(at)007Marketing(dot)com>, pgsql-hackers(at)postgresql(dot)org, sfrost(at)snowman(dot)net
Subject: Re: Syntax bug? Group by?
Date: 2006-10-17 17:55:34
Message-ID: 45351916.3040105@dunslane.net
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Mark Woodward wrote:
>> Stephen Frost wrote:
>>
>>
>>> select ycis_id, min(tindex), avg(tindex) from y where ycis_id = 15;
>>>
>> But back to the query the issue comes in that the ycis_id value is
>> included with the return values requested (a single row value with
>> aggregate values that isn't grouped) - if ycis_id is not unique you will
>> get x number of returned tuples with ycis_id=15 and the same min() and
>> avg() values for each row.
>> Removing the ycis_id after the select will return the aggregate values
>> you want without the group by.
>>
>
> I still assert that there will always only be one row to this query. This
> is an aggregate query, so all the rows with ycis_id = 15, will be
> aggregated. Since ycis_id is the identifying part of the query, it should
> not need to be grouped.
>
> My question, is it a syntactic technicality that PostgreSQL asks for a
> "group by," or a bug in the parser?
>
>

AFAIK what you want is not per sql spec. What if you had instead written

select ycis_id, min(tindex), avg(tindex) from y where frobnitz(ycis_id) = 15;

? I think you are expecting too much reasoning from the engine.

cheers

andrew

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