Why is it always impossible to get the correct value with round rounding?

Why is it always impossible to get the correct value with round rounding?
Author: cg1 Excerpt from: access911.net
Problem:


Why is it always impossible to get the correct value with round rounding?
Like what
Round (11.115,2) is equal to 1.11 instead of 1.12.


For example, I wrote the following statement in an Access query:
SELECT Round (0.005, 2) as ID;
The result is not 0.01 of what I expected, but 0, what should I do if I want to get 0.01?





Reply:

The reason is very simple, in the accurate calculation should use the "Currency" type field instead of the commonly used "digital" "double precision", should be the dual-precision storage method is not directly stored in the decimal, but with the scientific counting method, always produce errors.
If you must use double precision, it is recommended to store decimal places and integer digits separately.


About in queries you can use the following statement to resolve
SELECT Format (0.005, ' #.## ') as ID;