Обсуждение: Comparing dates

My date setting is ISO with US conventions, and output from a select
is in the form yyyy-mm-dd (2002-01-18, for example.

When I do a select such as

SELECT * FROM table WHERE date BETWEEN '2001-12-28' AND '2002-01-28'

It misses the entry with date '2002-01-28'  (which does exist!).

Likewise,

SELECT * FROM table WHERE date = '2001-12-28' ;

gives me '0 rows'.


The only way I've been able to handle this, so far, is
in this fashion:

SELECT * FROM table WHERE
    date BETWEEN 20011228 - .001 AND 20020128 + .001 ;

and similarly instead of = using, I can use

    date BETWEEN 20020128 - .001 AND 20020128 + .001


I must be missing something, but I can't find it.

What is the 'right' way to select for a date type = a particular
date, and for BETWEEN to work as advertised?

I have a copy of 'Practical Postgresql', but I can't find the
answer there, or in the online manual. Of course there are a
lot of places to look and I may have missed it.

Thanks,

John Velman

On Tue, Sep 02, 2003 at 04:09:00PM -0700, John Velman wrote:
> My date setting is ISO with US conventions, and output from a select
> is in the form yyyy-mm-dd (2002-01-18, for example.
>
> When I do a select such as
>
> SELECT * FROM table WHERE date BETWEEN '2001-12-28' AND '2002-01-28'
>
> It misses the entry with date '2002-01-28'  (which does exist!).

So, your date column is actually a timestamp?  Cast it to date first and
see if it works, e.g.

SELECT * FROM table WHERE date::date BETWEEN '2001-12-28' AND '2002-01-28'

--
Alvaro Herrera (<alvherre[a]dcc.uchile.cl>)
"La principal característica humana es la tontería"
(Augusto Monterroso)

"John Velman" <velman@cox.net> writes:
> When I do a select such as
> SELECT * FROM table WHERE date BETWEEN '2001-12-28' AND '2002-01-28'
> It misses the entry with date '2002-01-28'  (which does exist!).

Uh, what exactly is the datatype of the "date" column?

> The only way I've been able to handle this, so far, is
> in this fashion:
> SELECT * FROM table WHERE
>     date BETWEEN 20011228 - .001 AND 20020128 + .001 ;

I think the odds that this does what you think it does are vanishingly
small :-(.  There's no date-vs-numeric comparison operator.  It's
probably getting interpreted as some bizarre textual comparison.

            regards, tom lane