Re: "select c1, method(c2) group by c1" returns all values of c2 for c1 - Mailing list pgsql-sql

On 02/08/2011 02:51 PM, Rolando Edwards wrote:
> SELECT distinct c1,array_to_string(array(SELECT c2 FROM T1 B where A.c1=B.c1),', ') from T1 A order by c1;
>
> Give it a Try !!!


Thanks a lot! Very helpful!

array_to_string() + array() is exactly what I am looking for!

I just wonder that array_to_string() + array() will provide me good 
performance, right? If the calculation will be based on millions records.

Thanks again!
--
Lu Ying





> Rolando A. Edwards
> MySQL DBA (SCMDBA)
>
> 155 Avenue of the Americas, Fifth Floor
> New York, NY 10013
> 212-625-5307 (Work)
> 201-660-3221 (Cell)
> AIM&  Skype : RolandoLogicWorx
> redwards@logicworks.net
> http://www.linkedin.com/in/rolandoedwards
>
>
> -----Original Message-----
> From: pgsql-sql-owner@postgresql.org [mailto:pgsql-sql-owner@postgresql.org] On Behalf Of Emi Lu
> Sent: Tuesday, February 08, 2011 2:36 PM
> To: pgsql-sql@postgresql.org
> Subject: [SQL] "select c1, method(c2) group by c1" returns all values of c2 for c1
>
> Good afternoon,
>
> Is there a method to retrieve the following results:
>
> T1(c1 int, c2 varchar(128) )
> ---------------------------------
>
>
> (1, val1);
> (1, val2);
> (1, val3);
> (2, val1);
> (3, val5);
> (3, val6);
>
> select c1, method(c2)
> group by c1
>
> returns:
> ============
> 1,   "val1, val2, val3"
> 2,   "val1"
> 3,   "val5, val6"
>
>
> Thanks a lot!
>
> --
> Lu Ying
>


-- 
Emi Lu, ENCS, Concordia University, Montreal H3G 1M8
emilu@encs.concordia.ca        +1 514 848-2424 x5884