Re: [SQL] Week to date function
On 2010-03-27, Hiltibidal, Rob rob.hiltibi...@argushealth.com wrote: U 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. -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
Re: [SQL] Week to date function
U only 52 calendar weeks in a year... I'm almost sure that is the
norm
-Original Message-
From: pgsql-sql-ow...@postgresql.org
[mailto:pgsql-sql-ow...@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.
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Re: [SQL] Week to date function
Are you sure? http://en.wikipedia.org/wiki/ISO_8601 Week dates Main article: ISO week date http://en.wikipedia.org/wiki/ISO_week_date *-Www* *or* *Www* *-Www-D* *or* *WwwD* Week date representations are in the format as shown in the box to the right. [] 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 jgo...@gmail.com On Fri, Mar 26, 2010 at 07:48, Ireneusz Pluta ipl...@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
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.
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Re: [SQL] Week to date function
It isn't. The norm is defined by ISO 8601. 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 jgo...@gmail.com On Sat, Mar 27, 2010 at 18:31, Hiltibidal, Rob rob.hiltibi...@argushealth.com wrote: U only 52 calendar weeks in a year... I'm almost sure that is the norm
Re: [SQL] Week to date function
Sergey Konoplev pisze:
On 25 March 2010 12:25, Ireneusz Pluta ipl...@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
FROMgenerate_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
2010-03-22
2010-03-23
2010-03-24
2010-03-25
2010-03-26
2010-03-27
2010-03-28
(7 rows)
SELECT your_week2date(2009, 52) ;
your_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 your_week2date(2009, 53) ;
your_week2date
(0 rows)
SELECT your_week2date(2010, 1) ;
your_week2date
2010-01-04
2010-01-05
2010-01-06
2010-01-07
2010-01-08
2010-01-09
2010-01-10
(7 rows)
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Re: [SQL] Week to date function
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...@gmail.com / Skype: gray-hemp / ICQ: 29353802
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Re: [SQL] Week to date function
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
FROMgenerate_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
2009-12-28
2009-12-29
2009-12-30
2009-12-31
2010-01-01 cut
2010-01-02 cut
2010-01-03 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
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[SQL] Week to date function
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.
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, ''::text) -
interval '3 days')::date AS start,
(to_date($1::text, ''::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)
Re: [SQL] Week to date function
On 25 March 2010 12:25, Ireneusz Pluta ipl...@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, ''::text) - interval
'3 days')::date AS start,
(to_date($1::text, ''::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...@gmail.com / Skype: gray-hemp / ICQ: 29353802
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