Re: Horizontal aggregation?

On Sat, Apr 14, 2012 at 1:28 AM, Abel Abraham Camarillo Ojeda
<acamari(at)the00z(dot)org> wrote:
> On Sat, Apr 14, 2012 at 1:22 AM,  <hamann(dot)w(at)t-online(dot)de> wrote:
>>
>>
>> Hi,
>>
>> I am looking for a feature that would select from a table with
>> k1  a
>> k1  b
>> k1  c
>> k2  a
>> k3  b
>> k3  c
>> something like
>> k1  a b c
>> k2  a
>> k3  b c
>> (Just all elements next to each other, with a space in between)
>> or perhaps an array output
>> k1  {a,b,c]
>> k2  {a}
>> k3  {b,c}
>>
>> If such an operator exists, would there be a "remove duplicates" option?
>>
>> Regards
>> Wolfgang Hamann
>>
>>
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>
> select k, array_agg(distinct val ) from t;
>
> See the docs: http://www.postgresql.org/docs/9.1/static/sql-expressions.html#SYNTAX-AGGREGATES

obviously I forgot the group by:

select k, array_agg(distinct val ) from t group by k;