Thread: date comparision

Is anyone out here can give some advice?

i have a table with a timestamp field.
i should know if there is records for the particular year and month
so i need a query like (in MySQL it was very simple, but i should move to
postgres!):

SELECT something FROM mytable WHERE MONTH('timestamp_field')=07              AND YEAR('timestamp_field')=2000 LIMIT 1;

So, i am looking for date/time functions:

SELECT * FROM table WHERE date_part('year',timestamp 'timestamp_field') =
2000;

but it doesn't work...(ERROR:  Bad abstime external representation
'timestamp_field')
may be i need subselect or abstime(timestamp) function??

I suppose it's a lame q, but i cannot solve it today...
Thanks!

Thanks for your input. Unfortunately, it doesn't helped..

Here is the samples.

This query works fine:
SELECT datums_ FROM jaunumi WHERE flag = 'a' AND date_part('year',datetime
'2000-06-02 06:11:01-07') = '2000' LIMIT 1;
datums_
----------------------
2000-07-06 18:51:27+03
(1 row)

But this fails, obviously because the function doesnt know the value of
datums_:
SELECT datums_ FROM jaunumi WHERE flag = 'a' AND date_part('year',datetime
'datums_') = '2000' LIMIT 1;
ERROR:  Bad datetime external representation 'datums_'

datums_ is a timestamp field. How do i get it's value to use in date_part()
function??
date_part('year',datums_)   and date_part('year',datetime datums_) doesnt
work also!

----- Original Message -----
From: Jie Liang
To: sandis
Sent: Friday, July 07, 2000 11:19 PM
Subject: Re: [SQL] date comparision

Hi,
it works for me:
urldb=# \d deleted          Table "deleted" Attribute  |    Type     | Modifier
-------------+-------------+----------url         | text        |allocatedto | varchar(30) |deleteddate | timestamp
|id         | integer     | not null
 
Index: deleted_pkey
so , I 've a field deleteddate(type is timestamp) in table deleted.
urldb=# select deleteddate from deleted limit 10 offset 230000;     deleteddate
------------------------1999-12-17 15:24:19-081999-12-17 15:25:14-081999-12-17 15:25:29-081999-12-17
15:25:35-082000-01-1918:00:51-081999-12-17 15:27:02-081999-12-17 15:27:59-082000-01-19 18:00:54-081999-12-17
15:28:16-081999-12-1715:28:20-08
 

urldb=# select deleteddate from deleted where year(deleteddate)=2000
and rtrim(monthname(deleteddate),' ')='June'
and rtrim(dayname(deleteddate),' ')='Friday' limit 10;     deleteddate
------------------------2000-06-02 06:11:01-072000-06-02 06:16:08-072000-06-02 06:23:17-072000-06-02
06:23:17-072000-06-0206:23:17-072000-06-02 06:45:30-072000-06-02 06:49:55-072000-06-02 07:08:27-072000-06-02
07:13:21-072000-06-0207:13:21-07
 
(10 rows)
Good luck!!!
--
Jie LIANG

Internet Products Inc.

10350 Science Center Drive
Suite 100, San Diego, CA 92121
Office:(858)320-4873

jliang@ipinc.com
www.ipinc.com

On Mon, Jul 10, 2000 at 11:52:16AM +0300, sandis wrote:
> Thanks for your input. Unfortunately, it doesn't helped..
> 
> Here is the samples.
> 
> This query works fine:
> SELECT datums_ FROM jaunumi WHERE flag = 'a' AND date_part('year',datetime
> '2000-06-02 06:11:01-07') = '2000' LIMIT 1;
> datums_
> ----------------------
> 2000-07-06 18:51:27+03
> (1 row)
> 
> But this fails, obviously because the function doesnt know the value of
> datums_:
> SELECT datums_ FROM jaunumi WHERE flag = 'a' AND date_part('year',datetime
> 'datums_') = '2000' LIMIT 1;
> ERROR:  Bad datetime external representation 'datums_'
> 
> datums_ is a timestamp field. How do i get it's value to use in date_part()
> function??
> date_part('year',datums_)   and date_part('year',datetime datums_) doesnt
> work also!

Right, that's the syntax for a datetime literal, not a cast. How about:

SELECT datums_ FROM jaunumi WHERE flag = 'a' AND date_part('year', datetime(datums_)) = 2000 LIMIT 1;

By the way, what version are you using? The functional cast is needed for 
6.5.X, but not for 7.X.

Ross

-- 
Ross J. Reedstrom, Ph.D., <reedstrm@rice.edu> 
NSBRI Research Scientist/Programmer
Computer and Information Technology Institute
Rice University, 6100 S. Main St.,  Houston, TX 77005