Re: Querying date_time for date only ?

Aarni Ruuhimki wrote:
> Hello List,
>
> I have a time stamp without time zone field, YYYY-MM-DD hh:mm:ss, in
> my table. I want to also find something just for a particular day
> regardless of the time.
>
> (Pg)SQL way to do this ?

Yes. You can use date_trunc():

test=> select date_trunc('day', '2004-01-04 04:02:03'::timestamp);
date_trunc
---------------------
2004-01-04 00:00:00
(1 row)

so it would be date_trunc('day', col) = '2004-01-05'. The problem with
this is that you cannot use an index unless you create an expression
index on the date_trunc() function call. Another option is to do
something like:

WHERE col >= '2004-01-04' AND col < '2004-01-05'

If the date isn't a constant, you have to use date_trunc() on those, and
add one day to the second comparison:

WHERE col >= date_trunc('day', col2) AND
col < date_trunc('day', col2) + '1 day';

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