On Friday, August 19, 2011, Brandon Allbery <allbery.b@gmail.com> wrote:
> On Fri, Aug 19, 2011 at 11:45, Erik Hesselink <hesselink@gmail.com> wrote:
>>
>> Note that PostgreSQL also doesn't work with decimals as precision:
>>
>> postgres=# select 1::decimal(4,2) * 1::decimal(4,2);
>> ?column?
>> ----------
>>   1.0000
>> (1 row)
>>
>> That should be 1.00 instead if you want the precision correctly represented.
>
> Er?  Last I checked, that was exactly how precision worked over multiplication; otherwise you are incorrectly discarding precision present in the original values.  Unless you're assuming the OP actually wants an incorrect flat precision model....

This is the way I was taught to do it in physics. See also http://en.m.wikipedia.org/wiki/Significance_arithmetic

Erik

>
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