Re: float comparison?

[Joerg Bruehe]

Hi!

Scott Gifford wrote:
> Jerry Swanson <pmysql@stripped> writes:
> 
> 
>>Why when I do select from database and try to compare float field with float
>>number, I have no results
>>
>>amount --- type float
>>
>>select * from price where amount = 3.45 // doesn't work
>>select * from price where amount = '3.45' //doesn't work
> 
> 
> Floating point numbers are very rarely equal, because of small
> rounding errors that happen all the time.  [[...]]

This is the problem to convert fractions between the decimal and the 
binary system.

For a coarse analogy, try to express 1/3 exactly using a finite number 
of decimal digits.

For more info, AFAIK this is the standard reference:
http://cch.loria.fr/documentation/IEEE754/ACM/goldberg.pdf

Regards,
Jörg

-- 
Joerg Bruehe, Senior Production Engineer
MySQL AB, www.mysql.com