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Re: Date operations

From: Chetan Suttraway <chetan(dot)suttraway(at)enterprisedb(dot)com>
To: Barbara Figueirido <barbara(at)bariloche(dot)com(dot)ar>
Cc: pgsql-novice <pgsql-novice(at)postgresql(dot)org>
Subject: Re: Date operations
Date: 2011-03-02 12:09:58
Message-ID: AANLkTi=CWmW5_E8qjpuO860_YBf_yCKAe5ME4L-88Nys@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-novice
On Tue, Mar 1, 2011 at 5:47 PM, Barbara Figueirido <barbara(at)bariloche(dot)com(dot)ar
> wrote:

>  On 03/01/2011 08:14 AM, Chetan Suttraway wrote:
>
>
>
>> What I would like, if possible, is something on the line of "SELECT
>> DISTINCT ON file ..... WHERE date NOT GREATER THAN somedate [ORDER BY
>> date desc]" but cannot seem to find a way to do it.
>>
>> I would greatly appreciate any ideas on this subject, kind regards to all,
>> Barbara F.
>>
>
>
> Would it be possible to post the setup in terms of sql queries?
>
> Hello, thanks for your answer.
> The view in question has this definition:
> --
> CREATE VIEW olx_gst_exp AS
>     SELECT e.exp_name, e.exp_number, g.gest_fecha, g.gest_tipo FROM
> olx_expedient e, olx_gestiones g WHERE (e.exp_id = g.olx_exp_id) ORDER BY
> e.exp_name;
>
> whereas the corresponding tables have this setup:
>
> openlex=# \d olx_expedient
>                                              Table "public.olx_expedient"
>      Column            |           Type
> |            Modifiers
>
> ----------------+--------------------------+--------------------------------------------------------------------------
>  exp_number        | text                                    | not null
>  exp_ext_id           | integer                               |
>  crt_id                   | integer                               |
>  exp_sec_id           | integer                               |
>  exp_start             | timestamp with time zone | default now()
>  exp_end              | timestamp with time zone |
>  exp_user_stamp | character varying(64)        | default "current_user"()
>  exp_time_stamp | timestamp with time zone | default now()
>  exp_id                 | integer                               | not null
> default nextval(('"olx_expedient_exp_id_seq"'::text)::regclass)
>  exp_name          | character varying(64)        |
>  exp_nick             | text                                    |
> activo                 | boolean                              | default
> true
> ....
>
> and
>
> openlex=# \d olx_gestiones
>                                        Table "public.olx_gestiones"
>      Column           |           Type           |
> Modifiers
>
>
> ----------------+--------------------------+--------------------------------------------------------------
>  gest_id                | integer                  | default
> nextval(('"olx_gestiones_gest_id"'::text)::regclass)
>  gest_tipo             | text                       |
>  gest_fecha          | date                      | default
> ('now'::text)::date
>  olx_exp_id           | integer                  | not null
>  plazo                   | interval                 |
>  fechas_cl            | date                      |
>  vencim               | integer                  |
>  timestamp         | timestamp with time zone | default now()
>  fojas                   | integer                  |
>  exp_user_stamp | text                     | default "current_user"()
>
>
> I hope this is clear enough, thanks again for your response.
> Barbara F.
>
>
> --
> Dra. Bárbara M. Figueirido
> 25 de Mayo 1331
> 8400 S.C. de Bariloche - RIO NEGRO
> Argentina
> Tel.-Fax: +54 2944 456252
>                    15682745
>
>
I tried my own setup of queries. Not sure if this fits your requirement
though.


create table tab1(a int, t timestamp default now());
create table tab2(a int, t timestamp default now());
create view view1 as  select tab1.a a1, tab1.t t1,tab2.a a2, tab2.t t2 from
tab1,tab2 where tab1.a = tab2.a ;

--after inserting few record
pg=# select * from tab1;
 a |             t
---+---------------------------
 1 | 02-MAR-11 16:44:36.890285
 2 | 02-JAN-11 16:44:36.890285
 2 | 02-DEC-10 16:44:36.890285
 2 | 02-FEB-10 16:44:36.890285
(4 rows)

pg=# select * from tab2;
 a |             t
---+---------------------------
 1 | 02-MAR-11 16:44:36.890285
 2 | 02-JAN-11 16:44:36.890285
 2 | 02-DEC-10 16:44:36.890285
 2 | 02-FEB-10 16:44:36.890285
(4 rows)


Now tried below query to find records where the time difference between
current time and inserted time
is atleast 3 months. ie values of t1 or t2 which are older than 3 months wrt
current time.

pg=# select a1,t1 from view1 where age(now(),t1) > interval '3 mons' order
by t1;
 a1 |            t1
----+---------------------------
  2 | 02-FEB-10 16:44:36.890285
  2 | 02-FEB-10 16:44:36.890285
  2 | 02-FEB-10 16:44:36.890285
  2 | 02-DEC-10 16:44:36.890285
  2 | 02-DEC-10 16:44:36.890285
  2 | 02-DEC-10 16:44:36.890285
(6 rows)


Google pointed below links, which might be interesting :
http://archives.postgresql.org/pgsql-sql/2008-01/msg00164.php
http://wiki.postgresql.org/wiki/Working_with_Dates_and_Times_in_PostgreSQL

Please go through the Date/Time section of the pg documentation for more
details.


-- 
Chetan Sutrave
Senior Software Engineer
EnterpriseDB Corporation
The Enterprise Postgres Company
Phone: +91.20.30589523

Website: www.enterprisedb.com
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Subject: Re: Date operations
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