Обсуждение: How to split timestamps values by 24h slices ?

Hello !

I have a table that contains two timestamps (and some other fields that
does not matter here).

the_table
----------
pk_planning_id  ==> INT8 (primary key)
timestamp_start ==> (not null timestamp without time zone)
timestamp_stop  =+> (not null timestamp without time zone)


I would like to do a SELECT of that table, but by splitting by 24h day :

So, if I have one planning from 2009-03-30 14h50 to 2009-04-01 19h00, I
would like to get three lines in my SELECT result :

123 | 2009-03-30 14h50 | 2009-03-30 24h00
123 | 2009-03-31 00h00 | 2009-03-31 24h00
123 | 2009-04-01 00h00 | 2009-04-01 19h00

I was thinking of doing that by playing with three UNION requests
(beginning date, intermediate(s) date(s) and ending dates.

Am i going in the right way or is there a cleanest (or more elegant) way
to do that ?

Thanks in advance !

Regards,

--
Bruno Baguette

2009/3/29 Bruno Baguette <bruno.baguette@gmail.com>:
>
> I have a table that contains two timestamps (and some other fields that does
> not matter here).
>
> the_table
> ----------
> pk_planning_id  ==> INT8 (primary key)
> timestamp_start ==> (not null timestamp without time zone)
> timestamp_stop  =+> (not null timestamp without time zone)
>
>
> I would like to do a SELECT of that table, but by splitting by 24h day :
>
> So, if I have one planning from 2009-03-30 14h50 to 2009-04-01 19h00, I
> would like to get three lines in my SELECT result :
>
> 123 | 2009-03-30 14h50 | 2009-03-30 24h00
> 123 | 2009-03-31 00h00 | 2009-03-31 24h00
> 123 | 2009-04-01 00h00 | 2009-04-01 19h00
>
> I was thinking of doing that by playing with three UNION requests (beginning
> date, intermediate(s) date(s) and ending dates.
>
> Am i going in the right way or is there a cleanest (or more elegant) way to
> do that ?
>


Try:

bdteste=# \set ini '\'2009-03-30 14:50\'::timestamp'
bdteste=# \set fim '\'2009-04-01 19:00\'::timestamp'

bdteste=# SELECT CASE WHEN (:ini)::date + s.a = (:ini)::date THEN :ini
bdteste-#             ELSE (:ini)::date+s.a*'1 day'::interval
bdteste-#        END AS "Inicio",
bdteste-#        CASE WHEN (:ini)::date + s.a < (:fim)::date THEN
((:ini)::date+(s.a+1)*'1 day'::interval)-'1 second'::interval
bdteste-#             ELSE :fim
bdteste-#        END AS "Fim"
bdteste-#        FROM generate_series(0, extract(day from (:fim -
:ini))::int) as s(a);
       Inicio        |         Fim
---------------------+---------------------
 2009-03-30 14:50:00 | 2009-03-30 23:59:59
 2009-03-31 00:00:00 | 2009-03-31 23:59:59
 2009-04-01 00:00:00 | 2009-04-01 19:00:00
(3 registros)

Osvaldo

Bruno Baguette wrote:
> Hello !
>
> I have a table that contains two timestamps (and some other fields that
> does not matter here).
>
> the_table
> ----------
> pk_planning_id  ==> INT8 (primary key)
> timestamp_start ==> (not null timestamp without time zone)
> timestamp_stop  =+> (not null timestamp without time zone)
>
>
> I would like to do a SELECT of that table, but by splitting by 24h day :
>
> So, if I have one planning from 2009-03-30 14h50 to 2009-04-01 19h00, I
> would like to get three lines in my SELECT result :
>
> 123 | 2009-03-30 14h50 | 2009-03-30 24h00
> 123 | 2009-03-31 00h00 | 2009-03-31 24h00
> 123 | 2009-04-01 00h00 | 2009-04-01 19h00
>
> I was thinking of doing that by playing with three UNION requests
> (beginning date, intermediate(s) date(s) and ending dates.
>
> Am i going in the right way or is there a cleanest (or more elegant) way
> to do that ?
>
> Thanks in advance !
>
> Regards,
>

I'd suggest a calendar table. Depending on needs, you may want to fields
like day_of_week, quarter, term, moon_phase, whatever...


CREATE TABLE calendar (
    calendar_date date NOT NULL,
    CONSTRAINT calendar_pk PRIMARY KEY (calendar_date)
);

-- populate your table with suitable date ranges
INSERT INTO calendar
SELECT '2000-01-01'::date + i
FROM generate_series(0,10000) i;


Now change your original query like so:

SELECT *
FROM my_table
JOIN calendar ON calendar_date BETWEEN TRUNC(timestamp_start)
    AND timestamp_end

Artacus

Le 30/03/09 05:39, Osvaldo Kussama a écrit :
> 2009/3/29 Bruno Baguette <bruno.baguette@gmail.com>:
>> I would like to do a SELECT of that table, but by splitting by 24h day :
> Try:
>
> bdteste=# \set ini '\'2009-03-30 14:50\'::timestamp'
> bdteste=# \set fim '\'2009-04-01 19:00\'::timestamp'
>
> bdteste=# SELECT CASE WHEN (:ini)::date + s.a = (:ini)::date THEN :ini
> bdteste-#             ELSE (:ini)::date+s.a*'1 day'::interval
> bdteste-#        END AS "Inicio",
> bdteste-#        CASE WHEN (:ini)::date + s.a < (:fim)::date THEN
> ((:ini)::date+(s.a+1)*'1 day'::interval)-'1 second'::interval
> bdteste-#             ELSE :fim
> bdteste-#        END AS "Fim"
> bdteste-#        FROM generate_series(0, extract(day from (:fim -
> :ini))::int) as s(a);
>        Inicio        |         Fim
> ---------------------+---------------------
>  2009-03-30 14:50:00 | 2009-03-30 23:59:59
>  2009-03-31 00:00:00 | 2009-03-31 23:59:59
>  2009-04-01 00:00:00 | 2009-04-01 19:00:00
> (3 registros)
>
> Osvaldo

Really nice !

I under-estimasted the power of the generate_series() function and I
didn't thought using that function with date manipulation.

The calendar suggest of Artacus is also interesting but it needs to be
be regularly populated.

Regards,

--
Bruno Baguette