Обсуждение: how to "group" several records with same timestamp into one line?

zxo102 ouyang wrote:

> I would like to "group" them into one line with SQL like
>
>    1.5     MPa   2.5    M3  3.5  M3   4.5   t   2008-11-12 12:12:12

Look up the "GROUP BY" clause.

http://www.postgresql.org/docs/current/static/sql-select.html

Note that with timestamps you may have to truncate/round them to the
desired precision, since current versions of PostgreSQL store timestamps
in a floating point format and two timestamps you'd expect to be equal
may not end up being seen as exactly equal.

--
Craig Ringer

On Wed, Nov 12, 2008 at 3:59 AM, zxo102 ouyang <zxo102@gmail.com> wrote:
> Hi everyone,
>      My data with same timestamp "2008-11-12 12:12:12" in postgresql are as
> follows
>
> rowid  data   unit            channel          create_on
> ------------------------------------------------------------------------------
>  1        1.5     MPa          channel1  2008-11-12 12:12:12
>  2        2.5     M3           channel2   2008-11-12 12:12:12
>  3        3.5     M3           channel3   2008-11-12 12:12:12
>  4        4.5     t               channel4   2008-11-12 12:12:12
> ------------------------------------------------------------------------------
>
> I would like to "group" them into one line with SQL like
>
>    1.5     MPa   2.5    M3  3.5  M3   4.5   t   2008-11-12 12:12:12
>

Lookup the crosstab contrib functions.