From: Jasen Betts <jasen@xnet.co.nz>
To: pgsql-sql@postgresql.org
Subject: Re: help on select
Date: 21 Apr 2011 23:15:26 GMT
Message-ID: <ioqdqe$lb0$1@reversiblemaps.ath.cx> (raw)
References: <BANLkTinpuRYSkCkU7ovGojjAhbgXcLAP=g@mail.gmail.com>
On 2011-04-20, Saulo Venâncio <saulo.venancio@gmail.com> wrote:
> --bcaec52e65e9b2f22304a15f3840
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>
> Hi guys,
> I need your help.
> I have a table called medidas, in this table i have some ocurrences that ha=
> s
> id_medida(primary key) id_ponto (sec_key) and also datetime field as
> timestamp.
> i would like to know from a set of idpontos, e.g. 10,11,23,24.... how can i
> get the most recent date that is common to all??
> for example, if idponto das date 2011-02-03 but none of others have this
> date in the db i dont want this. i want one common for all..
> thanks.
the trick seems to be to GROUP BY datetime
and to use a HAVING clause to reject the unwanted groups using
count(distinct()) to ensure coverage of the list.
-- a table
create temp table medidas(id_medida serial,id_ponto integer,datetime timestamp);
-- some test data.
insert into medidas (id_ponto,datetime) select floor(random()*30+1),('today'::timestamp +
floor(generate_series(0,100000)/10)*'1s'::interval);
-- the query:
-- note you need to paste the list of number in two different places
-- in the query, postgres only counts the length once.
select datetime
from medidas
where id_ponto in (10,11,23,24,27)
group by datetime
having count(distinct(id_ponto)) = array_length( array[10,11,23,24,27],1)
order by datetime desc limit 1;
-- confirmation
select * from medidas where datetime = (
select datetime
from medidas
where id_ponto in (10,11,23,24,27)
group by datetime
having count(distinct(id_ponto)) = array_length(array[10,11,23,24,27],1)
order by datetime desc limit 1
)
order by id_ponto;
what's this for?
Are you looking at keno results to see how recently your pick would have won?
--
⚂⚃ 100% natural
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To: pgsql-sql@postgresql.org
Cc: jasen@xnet.co.nz
Subject: Re: help on select
In-Reply-To: <ioqdqe$lb0$1@reversiblemaps.ath.cx>
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