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From:Johan De Meersman Date:February 15 2013 10:43am
Subject:Re: MySQL 5.1: incorrect arithmetic calculation
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----- Original Message -----
> From: "Alex Keda" <admin@stripped>
> 

> mysql> SELECT SUM(`Amount`*`Cost`*(1-`Discont`)) as `Summ` FROM
> `WorksCompliteAgregate` WHERE (`ContractID` = 10369 AND `Month` = 497);

Based off the select you printed, this comes to EXACTLY 548.595 for the first row and 0
for the second row.


> mysql> SELECT SUM(`Amount`*`Cost`*(1-`Discont`)*100)/100 as `Summ` FROM
> `WorksCompliteAgregate` WHERE (`ContractID` = 10369 AND `Month` = 497);

The more detailed result here, though, seems to suggest that there's a longer fraction in
your table than is printed by your select. Would your column happen to be a Float?

> but, my desktop calculator gives the result 548.60

Which is the correct rounding for 548.595. Check if your column is a float, and if it is,
go google for floating point mathematics. They do not work the way you think they do. Use
decimal(n,m) for money - or any discrete number, for that matter. Floats are not exact
values, they are APPROXIMATE values.

https://dev.mysql.com/doc/refman/5.0/en/problems-with-float.html may also give you an idea
of what goes wrong.


-- 
Unhappiness is discouraged and will be corrected with kitten pictures.
Thread
MySQL 5.1: incorrect arithmetic calculationAlex Keda15 Feb
  • Re: MySQL 5.1: incorrect arithmetic calculationJohan De Meersman15 Feb
    • Re: MySQL 5.1: incorrect arithmetic calculationAlex Keda15 Feb
      • Re: MySQL 5.1: incorrect arithmetic calculationAlex Keda15 Feb
        • Re: MySQL 5.1: incorrect arithmetic calculationJohan De Meersman15 Feb
  • Re: MySQL 5.1: incorrect arithmetic calculationmisiaq15 Feb
  • RE: MySQL 5.1: incorrect arithmetic calculationRick James21 Feb