Thread: BUG #7824: documentation bug: Extract DOW

The following bug has been logged on the website:

Bug reference:      7824
Logged by:          Tim Romano
Email address:      tim.romano@yahoo.com
PostgreSQL version: 9.2.2
Operating system:   Windows 7 x64
Description:        =


Documentation seems to indicate that only a Timestamp value is a valid
argument to the Extract function when trying to get the DOW, but a Date also
works:

dow =

The day of the week (0 - 6; Sunday is 0) (for timestamp values only)

SELECT EXTRACT(DOW FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 5

On Wed, Jan 23, 2013 at 2:10 AM, <tim.romano@yahoo.com> wrote:

> The following bug has been logged on the website:
>
> Bug reference:      7824
> Logged by:          Tim Romano
> Email address:      tim.romano@yahoo.com
> PostgreSQL version: 9.2.2
> Operating system:   Windows 7 x64
> Description:
>
> Documentation seems to indicate that only a Timestamp value is a valid
> argument to the Extract function when trying to get the DOW, but a Date
> also
> works:
>
> dow
> The day of the week (0 - 6; Sunday is 0) (for timestamp values only)
>
>
The document also mentions:
"(Expressions of type date will be cast to timestamp and can therefore be
used as well.)"

ISTM that "for timestamp values only" means that a source of type interval
or time can not b used. Other functions will also accept those additional
types. I don't know if the documentation needs to make that more clear
though.

Thanks,
Pavan

--
Pavan Deolasee
http://www.linkedin.com/in/pavandeolasee

On Tue, Jan 22, 2013 at 08:40:30PM +0000, tim.romano@yahoo.com wrote:
> The following bug has been logged on the website:
>
> Bug reference:      7824
> Logged by:          Tim Romano
> Email address:      tim.romano@yahoo.com
> PostgreSQL version: 9.2.2
> Operating system:   Windows 7 x64
> Description:
>
> Documentation seems to indicate that only a Timestamp value is a valid
> argument to the Extract function when trying to get the DOW, but a Date also
> works:
>
> dow
> The day of the week (0 - 6; Sunday is 0) (for timestamp values only)
>
> SELECT EXTRACT(DOW FROM TIMESTAMP '2001-02-16 20:38:40'); Result: 5

[Sorry for the late reply.]

I assume you mean:

    SELECT EXTRACT(DOW FROM DATE '2001-02-16');
     date_part
    -----------
             5
    (1 row)

That does work fine, and is documented in PG 9.2:

    http://www.postgresql.org/docs/9.2/static/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT
    The extract function retrieves subfields such as year or hour from
    date/time values. source must be a value expression of type timestamp,
-->    time, or interval. (Expressions of type date are cast to timestamp and
-->    can therefore be used as well.)

Where did you see that DATE is not supported for EXTRACT?

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +