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

W dniu 03/24/2013 12:11 PM, Rafał Pietrak pisze:
> W dniu 03/24/2013 12:06 PM, Misa Simic pisze:
>> maybe,
>>
>> SELECT DISTINCT issuer,amount, array_agg(REFERENCE) over (partition
>> by invoice_nr) from invoices;
>
> RIGHT. Thenx. (and the first thing I did, I've read the doc on
> array_agg().... what stress makes from people :(
>

Actually, I have a problem with that (which I haven't noticed earlier
because the data I'm having, don't have to many "duplicates" that cause
it). The problem is, that:
--------------------------------------
SELECT DISTINCT a, b, c, array_agg(k.d) OVER (PARTITION BY k.c ) FROM
testy k where k.e <> 'email' and k.c='1035049' ;
a | b | c | array_agg
------+----------+---------+-------------------------------
1035 | 10410053 | 1035049 | {9902031328529,5951948640868}
---------------------------------------

is _almost_ fine. But I actually need to have control over the order in
which the array gathered its values. So I try:
------------------------------------
SELECT DISTINCT a, b, c, array_agg(k.d) OVER (PARTITION BY k.c ORDER BY
k.e) FROM testy k where k.e <> 'email' and k.c='1035049' ;
a | b | c | array_agg
------+----------+---------+-------------------------------
1035 | 10410053 | 1035049 | {5951948640868}
1035 | 10410053 | 1035049 | {5951948640868,9902031328529}
(2 rows)
--------------------------------------

And this is not at all what I've expected - the aggerate function
returned different values over the selected partition.

I understand, that this behavior (of changing the aggregate function
return values) is there for the purpose of having sum() - and the like -
aggregate functions return accumulating/averaged/etc values as of the
example in postgres documentation (
http://www.postgresql.org/docs/9.1/static/tutorial-window.html)

But the array_agg() is significantly different from other aggregate
functions - it maintains all the trasspassed values within; under such
circumstances: is it reasonable to copy that functionality (of PARTITION
OVER ... ORDER BY...) in it?
A particular value relevant to a particular row (when SELECT withiout
DISTINCT) can be retrieved by RANK() function used as an index into the
resulting array.

But, if (unfortunately) this functionality have to stay: Can somebody
pls help me cooking an SQL that returns the same value of array_agg()
over the entire partition, while letting me control the order of
aggregated values, based on the order of column "E"?

My table for the showcase was:
-----------------------------------
SELECT * FROM testy;
a | b | c | d | e
------+----------+---------+----------------------+-------
1035 | 10410053 | 1035049 | 9902031328529 | tel
1035 | 10410053 | 1035049 | 5291286807(at)gmail(dot)com | email
1035 | 10410053 | 1035049 | 5951948640868 | tel2
(3 rows)
------------------------------------------

thx

-R