On Wed, Sep 14, 2016 at 4:49 AM, Patrick B <patrickbakerbr@xxxxxxxxx> wrote:
2016-09-14 13:17 GMT+12:00 David Rowley <david.rowley@xxxxxxxxxxxxxxx>: On 14 September 2016 at 12:20, Patrick B <patrickbakerbr@xxxxxxxxx> wrote:
> I want to select all rows that have been modified from now to 4 months ago.
>
> I've used these queries:
>
>> select
>> modified_date,
>> from
>> clients
>> WHERE
>> modified_date BETWEEN '2016-06-13' AND '2016-09-13'
>
Going by my clock here 2016-06-13 was just over 3 months ago, not 4.
>> select
>> modified_date,
>> from
>> clients
>> WHERE
>> modified_date >='2016-06-13' AND modified_date < '2016-09-13'
>
>
>
> But it didn't work... it returns 0 rows.... but there are rows to be shown:
>
>
>> select modified_date from clients ORDER BY modified_date ASC
>
>
>
>> modified_date
>> -------------------
>> 2015-07-11 17:23:40
>> 2016-09-13 20:00:51
>> 2016-09-13 20:00:51
>> 2016-09-13 20:00:51
>> 2016-09-13 20:00:51
>
>
>
> What am I doing wrong?
None of those dates are between your specified date range. If you want
to include all of 2016-09-13 timestamps, then you'd better do <
'2016-09-14' since < '2016-09-13' will only cover timestamps on the
12th or before.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
Thanks guys...I've used < and >not sure why wasn't working before :(Thanks!
Patrick
It didn't work before because, as excellently pointed out by Vitaly Burovoy, because
modified_date BETWEEN '2016-06-13' AND '2016-09-13'
is evaluated as
modified_date >= '2016-06-13 00:00:00' AND modified_date <= '2016-09-13 00:00:00'
None of your timestamps falls in that range. '2016-09-13 20:00:51' is 20 hours and 51 seconds after the end of this range, and '2015-07-11 17:23:40' is more than a year before it.
Similar logic applies to modified_date >= '2016-06-13 00:00:00' AND modified_date < '2016-09-13 00:00:00'
Now, the reason it is working for you now, is probably because you're in a timezone where it is already 2016-09-14, and your WHERE clause now reads:
modified_date >= '2016-06-14 00:00:00' AND modified_date < '2016-09-14 00:00:00'
with the effect that the timestamp '2016-09-13 20:00:51' now falls within the range of your new WHERE clause.
At least, that's my suspicion.
Kind regards,
Na-iem Dollie
