Re: date_trunct() and start of week - Mailing list pgsql-general

From Thom Brown
Subject Re: date_trunct() and start of week
Date
Msg-id bddc86150911261417n5ed5e0a7s4e9e7e092132ce0f@mail.gmail.com
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In response to date_trunct() and start of week  (Thomas Kellerer <spam_eater@gmx.net>)
List pgsql-general
2009/11/26 Thomas Kellerer <spam_eater@gmx.net>
Hi,

while using date_trunc('week', some_date) to get the date of the first day of the week I noticed that it was working as expected: Monday is considered the start of the week.
I assume this depends on some locale setting, but I can't figure out which it is, so I can make sure this is not "accidently" changed. I tried changing LC_TIME (American_America) but that still returned Monday as the first day (my understanding is that in the States Sunday is considered the start of the week)

Any pointers are appreciated (did I miss it in the manual?)

Regards
Thomas


I don't understand how date_trunc is giving you the day of the week.  As far as I'm aware it only reduces the precision of the date/time.  What I imagine you'd use is: extract(DOW from some_date).  This won't be locale-dependant.  It will always be 0 (Sunday) - 6 (Saturday).  There is another way to get the day of the week which is to_char(some_date, 'D') which is numbered 1 (Sunday) to 7 (Saturday).

Regards

Thom

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