On 03/29/2011 08:50 AM, Adrian Klaver wrote:
On Tuesday, March 29, 2011 8:33:59 am Steve Crawford wrote:
On 03/29/2011 08:07 AM, Marc Munro wrote:
I'm trying to validate a day of the week, and thought that to_date would
do the job for me. But I found a case where it cannot tell the
difference between sunday and monday. Is this a bug or intended
behaviour?
dev=# select to_date('2011-13-Mon', 'YYYY-IW-DY');
to_date
------------
2011-03-28
Based on running the queries in 9.0, it's behavior that has been corrected:
select to_date('Mon1-13-Tue', 'YYYY-IW-DY');
ERROR: invalid combination of date conventions
HINT: Do not mix Gregorian and ISO week date conventions in a
formatting template.
Cheers,
Steve
Yes and no:)
test(5432)aklaver=>select to_date('2011-13-MON', 'IYYY-IW-DY');
to_date
------------
2011-03-28
(1 row)
test(5432)aklaver=>select to_date('2011-13-SUN', 'IYYY-IW-DY');
to_date
------------
2011-03-28
(1 row)
But you changed it to specify an ISO year avoiding the mixed
conventions. According to the 9.0 docs
(http://www.postgresql.org/docs/9.0/static/functions-formatting.html):
"An ISO week date (as distinct from a Gregorian date) can be specified
to to_timestamp and to_date in one of two ways:
Year, week, and weekday: for example to_date('2006-42-4',
'IYYY-IW-ID') returns the date 2006-10-19. If you omit the weekday it is
assumed to be 1 (Monday).
Year and day of year: for example to_date('2006-291',
'IYYY-IDDD') also returns 2006-10-19.
Attempting to construct a date using a mixture of ISO week and Gregorian
date fields is nonsensical, and will cause an error. In the context of
an ISO year, the concept of a "month" or "day of month" has no meaning.
In the context of a Gregorian year, the ISO week has no meaning. Users
should avoid mixing Gregorian and ISO date specifications. "
So I guess the upshot is that 9.0 throws errors on mixed input, but the
OP's issues can probably be resolved by explicitly specifying an ISO
year in the formatting.
Cheers,
Steve
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