Обсуждение: Week to date function
<font face="Courier New, Courier, monospace">Hello,<br /><br /> is there any standard function, or a concise solution
basedon set of them, returning a set of dates included in a week of given year and week number? <br /> I ended up with
creatingmy own function as in the example below, but I am curious if I am not opening an open door. <br /><br />
Thanks<br/><br /> Irek.<br /><br /> CREATE OR REPLACE FUNCTION week2date(double precision, double precision) RETURNS
SETOFdate<br /> AS<br /> $_$<br /> SELECT day<br /> FROM (<br /> SELECT to_char(day, 'IYYY')::integer AS
iyyy,<br/> to_char(day, 'IW' )::integer AS iw,<br /> day<br /> FROM (<br />
SELECT start + generate_series(0, n) AS day<br /> FROM (<br /> SELECT start,<br />
(stop - start)::integer AS n<br /> FROM (<br /> SELECT
(to_date($1::text,'YYYY'::text) - interval '3 days')::date AS start,<br />
(to_date($1::text,'YYYY'::text) + interval '1 year 3 days')::date AS stop<br /> ) ss<br />
) aa<br /> ) bb<br /> ) cc<br /> WHERE iw = $2 AND iyyy = $1<br /> ORDER<br /> BY day<br />
$_$<br/> LANGUAGE SQL<br /> IMMUTABLE<br /> ;<br /><br /> SELECT week2date(date_part('year', now()), date_part('week',
now()));<br/> week2date<br /> ------------<br /> 2010-03-22<br /> 2010-03-23<br /> 2010-03-24<br /> 2010-03-25<br
/> 2010-03-26<br /> 2010-03-27<br /> 2010-03-28<br /> (7 rows)<br /><br /> SELECT week2date(2009, 53);<br />
week2date<br/> ------------<br /> 2009-12-28<br /> 2009-12-29<br /> 2009-12-30<br /> 2009-12-31<br />
2010-01-01<br/> 2010-01-02<br /> 2010-01-03<br /> (7 rows)<br /><br /> SELECT week2date(2010, 1);<br />
week2date<br/> ------------<br /> 2010-01-04<br /> 2010-01-05<br /> 2010-01-06<br /> 2010-01-07<br />
2010-01-08<br/> 2010-01-09<br /> 2010-01-10<br /> (7 rows)<br /><br /></font>
On 25 March 2010 12:25, Ireneusz Pluta <ipluta@wp.pl> wrote:
> Hello,
>
> is there any standard function, or a concise solution based on set of them,
> returning a set of dates included in a week of given year and week number?
> I ended up with creating my own function as in the example below, but I am
> curious if I am not opening an open door.
Try to think of something like this?
SELECT date_trunc('week', '2010-01-01'::date) + '12 week'::interval + (d::text||' day')::interval
FROM generate_series(0, 6) AS d;
>
> Thanks
>
> Irek.
>
> CREATE OR REPLACE FUNCTION week2date(double precision, double precision)
> RETURNS SETOF date
> AS
> $_$
> SELECT day
> FROM (
> SELECT to_char(day, 'IYYY')::integer AS iyyy,
> to_char(day, 'IW' )::integer AS iw,
> day
> FROM (
> SELECT start + generate_series(0, n) AS day
> FROM (
> SELECT start,
> (stop - start)::integer AS n
> FROM (
> SELECT (to_date($1::text, 'YYYY'::text) - interval
> '3 days')::date AS start,
> (to_date($1::text, 'YYYY'::text) + interval '1 year
> 3 days')::date AS stop
> ) ss
> ) aa
> ) bb
> ) cc
> WHERE iw = $2 AND iyyy = $1
> ORDER
> BY day
> $_$
> LANGUAGE SQL
> IMMUTABLE
> ;
>
> SELECT week2date(date_part('year', now()), date_part('week', now()));
> week2date
> ------------
> 2010-03-22
> 2010-03-23
> 2010-03-24
> 2010-03-25
> 2010-03-26
> 2010-03-27
> 2010-03-28
> (7 rows)
>
> SELECT week2date(2009, 53);
> week2date
> ------------
> 2009-12-28
> 2009-12-29
> 2009-12-30
> 2009-12-31
> 2010-01-01
> 2010-01-02
> 2010-01-03
> (7 rows)
>
> SELECT week2date(2010, 1);
> week2date
> ------------
> 2010-01-04
> 2010-01-05
> 2010-01-06
> 2010-01-07
> 2010-01-08
> 2010-01-09
> 2010-01-10
> (7 rows)
>
>
--
Sergey Konoplev
Blog: http://gray-hemp.blogspot.com /
Linkedin: http://ru.linkedin.com/in/grayhemp /
JID/GTalk: gray.ru@gmail.com / Skype: gray-hemp / ICQ: 29353802
Sergey Konoplev pisze:
> On 25 March 2010 12:25, Ireneusz Pluta <ipluta@wp.pl> wrote:
>
>> Hello,
>>
>> is there any standard function, or a concise solution based on set of them,
>> returning a set of dates included in a week of given year and week number?
>> I ended up with creating my own function as in the example below, but I am
>> curious if I am not opening an open door.
>>
>
> Try to think of something like this?
>
> SELECT
> date_trunc('week', '2010-01-01'::date) +
> '12 week'::interval +
> (d::text||' day')::interval
> FROM generate_series(0, 6) AS d;
>
>
Yes, much smarter.
However, would give the same results on (year=2009, week=53) and
(year=2010, week=1). In fact, 2009 did not have week 53.
I wrapped it into a function with additional isoyear check and now seems OK.
Thanks
CREATE OR REPLACE FUNCTION your_week2date(double precision, double
precision) RETURNS SETOF date
AS
$_$
SELECT day
FROM ( SELECT ( date_trunc('week', ($1::text||'-01-01')::date) + ($2::text||'
week')::interval + ( d::text||' day')::interval )::date AS day FROM generate_series(0,
6)AS d
) alias
WHERE to_char(day, 'IYYY')::integer = $1
ORDER
BY 1
$_$
LANGUAGE SQL
IMMUTABLE
;
SELECT week2date1(date_part('year', now()), date_part('week', now()));week2date1
------------2010-03-222010-03-232010-03-242010-03-252010-03-262010-03-272010-03-28
(7 rows)
SELECT your_week2date(2009, 52) ;your_week2date
----------------2009-12-282009-12-292009-12-302009-12-312010-01-012010-01-022010-01-03
(7 rows)
SELECT your_week2date(2009, 53) ;your_week2date
----------------
(0 rows)
SELECT your_week2date(2010, 1) ;your_week2date
----------------2010-01-042010-01-052010-01-062010-01-072010-01-082010-01-092010-01-10
(7 rows)
> CREATE OR REPLACE FUNCTION your_week2date(double precision, double
> precision) RETURNS SETOF date
> AS
> $_$
> SELECT day
> FROM (
> SELECT (
> date_trunc('week', ($1::text||'-01-01')::date)
> + ($2::text||' week')::interval
> + ( d::text||' day')::interval
> )::date AS day
> FROM generate_series(0, 6) AS d
> ) alias
> WHERE to_char(day, 'IYYY')::integer = $1
> ORDER
> BY 1
> $_$
> LANGUAGE SQL
> IMMUTABLE
I think it is better to use date_part('year', day) instead of
to_char(...). And may be it is worth to do raise exception when
incorrect week specified.
--
Sergey Konoplev
Blog: http://gray-hemp.blogspot.com /
Linkedin: http://ru.linkedin.com/in/grayhemp /
JID/GTalk: gray.ru@gmail.com / Skype: gray-hemp / ICQ: 29353802
Sergey Konoplev pisze:
>> CREATE OR REPLACE FUNCTION your_week2date(double precision, double
>> precision) RETURNS SETOF date
>> AS
>> $_$
>> SELECT day
>> FROM (
>> SELECT (
>> date_trunc('week', ($1::text||'-01-01')::date)
>> + ($2::text||' week')::interval
>> + ( d::text||' day')::interval
>> )::date AS day
>> FROM generate_series(0, 6) AS d
>> ) alias
>> WHERE to_char(day, 'IYYY')::integer = $1
>> ORDER
>> BY 1
>> $_$
>> LANGUAGE SQL
>> IMMUTABLE
>>
>
> I think it is better to use date_part('year', day) instead of
> to_char(...).
this might cut first or last week in the year, like this:
SELECT your_week2date(2009, 52) ;your_week2date
----------------2009-12-282009-12-292009-12-302009-12-312010-01-01 cut2010-01-02 cut2010-01-03 cut
(7 rows)
which is not what I want when playing with isoweeks.
> And may be it is worth to do raise exception when
> incorrect week specified.
>
but, maybe, controlled by an additonal parameter saying if one prefers
to have exception or rather an empty resultset
Are you sure?
--
Jorge Godoy <jgodoy@gmail.com>
Week dates
Main article: ISO week date
YYYY-Www or YYYYWww YYYY-Www-D or YYYYWwwD Week date representations are in the format as shown in the box to the right. [YYYY] indicates the ISO week-numbering year which is slightly different to the calendar year (see below). [Www] is the week number prefixed by the letter 'W', from W01 through W53. [D] is the weekday number, from 1 through 7, beginning with Monday and ending with Sunday. This form is popular in the manufacturing industries.
There are mutually equivalent descriptions of week 01:
- the week with the year's first Thursday in it (the formal ISO definition),
- the week with 4 January in it,
- the first week with the majority (four or more) of its days in the starting year, and
- the week starting with the Monday in the period 29 December – 4 January.
If 1 January is on a Monday, Tuesday, Wednesday or Thursday, it is in week 01. If 1 January is on a Friday, Saturday or Sunday, it is in week 52 or 53 of the previous year (there is no week 00). 28 December is always in the last week of its year.
The week number can be described by counting the Thursdays: week 12 contains the 12th Thursday of the year.
In 2009, January 1st. happened on a Thursday.
As Jan 1st, 2010 happened on a Friday, it was on week 53 of 2009.
--
Jorge Godoy <jgodoy@gmail.com>
On Fri, Mar 26, 2010 at 07:48, Ireneusz Pluta <ipluta@wp.pl> wrote:
Yes, much smarter.
However, would give the same results on (year=2009, week=53) and (year=2010, week=1). In fact, 2009 did not have week 53.
I wrapped it into a function with additional isoyear check and now seems OK.
Thanks
Jorge Godoy pisze: > Are you sure? > > http://en.wikipedia.org/wiki/ISO_8601 snip > > As Jan 1st, 2010 happened on a Friday, it was on week 53 of 2009. you are right, thanks for pointing that out. I didn't check the opposite way like this: select date_part('week', '2010-01-01'::date);date_part ----------- 53 I need to recheck my code.
It isn't. The norm is defined by ISO 8601.
--
Jorge Godoy <jgodoy@gmail.com>
There is a lot of "fun" into date calculations.
The rule is to counts the number of Thursdays on a year to get the correct number of weeks.
What bothers me more is that here it is cultural that weeks start on Sunday, but ISO 8601 says they start on Monday. In Portuguese, the word for Monday can also be translated as "Second", as in "Second day". How to say that the second day is in fact the first? :-)
--
Jorge Godoy <jgodoy@gmail.com>
On Sat, Mar 27, 2010 at 18:31, Hiltibidal, Rob <Rob.Hiltibidal@argushealth.com> wrote:
Uhhhh only 52 calendar weeks in a year... I'm almost sure that is the
norm
Uhhhh only 52 calendar weeks in a year... I'm almost sure that is the norm -----Original Message----- From: pgsql-sql-owner@postgresql.org [mailto:pgsql-sql-owner@postgresql.org] On Behalf Of Ireneusz Pluta Sent: Saturday, March 27, 2010 3:22 PM To: Jorge Godoy Cc: Sergey Konoplev; pgsql-sql@postgresql.org Subject: Re: [SQL] Week to date function Jorge Godoy pisze: > Are you sure? > > http://en.wikipedia.org/wiki/ISO_8601 snip > > As Jan 1st, 2010 happened on a Friday, it was on week 53 of 2009. you are right, thanks for pointing that out. I didn't check the opposite way like this: select date_part('week', '2010-01-01'::date);date_part ----------- 53 I need to recheck my code. -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql PRIVILEGED AND CONFIDENTIAL This email transmission contains privileged and confidential information intended only for the use of the individual or entitynamed above. If the reader of the email is not the intended recipient or the employee or agent responsible for deliveringit to the intended recipient, you are hereby notified that any use, dissemination or copying of this email transmissionis strictly prohibited by the sender. If you have received this transmission in error, please delete the emailand immediately notify the sender via the email return address or mailto:postmaster@argushealth.com. Thank you.
On 2010-03-27, Hiltibidal, Rob <Rob.Hiltibidal@argushealth.com> wrote: > Uhhhh only 52 calendar weeks in a year... I'm almost sure that is the > norm All hours have 60 minutes All weeks have 7 days All years have 12 months all else is variable.