Re: is there a way to deliver an array over column from a query window?

SELECT DISTINCT a, b, c, array_agg(d) OVER (PARTITION BY c ) FROM

(

SELECT a, b, c, d FROM testy where e <> 'email' and c='1035049' ORDER BY
a, b, c, e

) t

Doesnt give u desired result?

On Friday, April 26, 2013, Rafał Pietrak wrote:

> W dniu 04/26/2013 05:25 PM, Tom Lane pisze:
>
>> =?ISO-8859-2?Q?Rafa=B3_**Pietrak?= <rafal(at)ztk-rp(dot)eu> writes:
>>
>>> array_agg(distinct v order by v) -- works in postgres, but actually I
>>> need:
>>> array_agg(distinct v order by v,x) -- which doesn't. (ERROR:
>>> ....expressions must appear in argument list),
>>>
>> Why do you think you need that? AFAICS, the extra order-by column could
>> not in any way affect the result of the operation.
>>
>
> In my particular case (e.g. not in general, since I assume, we all agree,
> that people do sort things comming out of the query for one purpose or
> another), is that:
> 1. the information i retrieve (the V), is a telephone number.
> 2. my database does keep numerous contact information (e.g. telephone
> numbers, email, etc) for "entities" registered here - e.g people/companies
> leave contact information of various relevance: my-private, my-office,
> my-lawyer, etc.
> 3. when I need to get in touch with somebody, I need to choose the number
> that is "most relevant" - one person leaves "my-private" phone, and
> "my-lawyer" phone; the other leaves "my-office", and "my-lawyer".
> 4. in the above example I'd like to peek: "my-private" for the first
> person, and "my-office" for the other. I wouldn't like to relay on
> randomness provided by the database query plan.
> 5. so I have "the other" column (the X, e.g "my-something"), that I'd like
> to sort the array elements by. And peek just the first element of the array.
>
> BTW: I've just rid off the array, and cooked a plain table join with
> "distinct on ()", which gives just what I needed. My initial plan of using
> array was to reduce the intermediate row-sets as much as possible as early
> as possible. Yet, in this case, plain old RDB joins proved to be better
> (may be not faster - a big multitable join is formed along the query, but
> conceptually cleaner, which works for me, the database isn't terribly big).
>
> So I have my problem solved, although I haven't figured out a way to have
> controll over the sort order of array_agg() result - which might be
> otherwise usefull.
>
> thnx,
>
> -R
>
>
>
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