On Fri, 11 Dec 2015 16:21:30 +0200 "Frank Millman" <frank at chagford.com> wrote:
> sqlite> UPDATE fmtemp SET balance = balance + 123.45; > sqlite> SELECT bal FROM fmtemp; > 5925.59999999999 To a question like that you'll receive a lot of answers about numerical accuracy. And it's true that there are ways to "do the math" without using floating point representation. It's also true that it's rarely necessary, which is why floating point representation exists and *is* widely used. You may find it works for you too, unless you have to adhere to a specific rounding policy. Per your example, you're working with 2 decimal places of precision. 5925.59999999999 rounds off to 5925.60; it even rounds off to 5925.6000000000, not too shabby. If you keep adding 123.45 to it, you'll find you can go on forever before the answer is wrong in the second decimal place. IEEE 754 is a solid bit of engineering. It's capable of representing 15 decimal digit of precision. That's good enough to measure the distance to the moon ... in millimeters. You could have an exceptional situation, but that would be exceptional. Usually, double-precision math works just fine, provided you have some form of round(3) at your disposal when it comes time to render the value in decimal form. --jkl
