On 3/26/2010 12:12 PM, Tom Lane wrote:
> "Gaietti, Mauro \(SELEX GALILEO Guest, Italy\)"<mauro.gaietti@xxxxxxxxxxxxxxxxxxxxxxx> writes:
>
>> This query:
>> select round(0.5), round(0.5::integer), round(0.5::bigint), round(
>> 0.5::float ), round( 0.5::double precision ),round(cast(0.5 as double
>> precision )),round(cast(0.5::double precision as numeric )); has strange
>> result:
>> 1 1 1 0 0 0 1
>>
>> Is this correct?
>>
> On most machines the float4/float8 operations follow the IEEE-754 spec's
> "round to nearest even" rule for such cases. I think all the other ones
> are "add 0.5 and truncate" implementations. It's unlikely we'll mess
> with either; and *highly* unlikely that we would change the float
> behavior since that's not even under our direct control (the hardware or
> libm is what's doing that). There's some case to be made for making
> numeric and integer math do it the IEEE way, but I think that would
> displease at least as many people as it pleased ...
>
> regards, tom lane
>
>
This topic keeps coming up every few months about rounding which way is
correct. I would be in favor of adding a option to round() function to
specify method.
Leave the defaults as they are for backwards capability, meaning if no
option is passed to Round() it follows current methods. I agree
changing how it works now would annoy many.
The option would be very simple something like this
Round( 0.5, RoundToEven) = 0
Round( -0.5, RoundToEven) = 0
Round(0.5, RoundUp) = 1
Round(-0.5, RoundUp) = 0
Round(0.5, RoundDown) = 0
Round(-0.5, RoundDown) = -1
Round(0.5, RoundToZero) = 0
Round(-0.5, RoundToZero) = 0
There are so many methods of rounding to choose from
http://en.wikipedia.org/wiki/Rounding
All legitimate Magwerks Corporation quotations are sent in a .PDF file attachment with a unique ID number generated by our proprietary quotation system. Quotations received via any other form of communication will not be honored.
CONFIDENTIALITY NOTICE: This e-mail, including attachments, may contain legally privileged, confidential or other information proprietary to Magwerks Corporation and is intended solely for the use of the individual to whom it addresses. If the reader of this e-mail is not the intended recipient or authorized agent, the reader is hereby notified that any unauthorized viewing, dissemination, distribution or copying of this e-mail is strictly prohibited. If you have received this e-mail in error, please notify the sender by replying to this message and destroy all occurrences of this e-mail immediately.
Thank you.
--
Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general
