Hi,
Thank you all for your comments.
Finally, I think I will simply use the data type NUMERIC instead of REAL
in all my columns !!
This type is more appropriate to store prices !
Philippe Ferreira.
Try this:
SELECT 13.95 = 13.95::real;
It should yield false, because the first number constant is presumed
to be of type numeric, which is an exact format, and the second
constant is explicitly cast to a single precision floating point
number, in which it doesn't fit*, and therefore actually is stored as
13.9499998**. So, the comparison is in fact 13.95=13.9499998, which
of course is false.
To see the effect in another way, try:
SELECT 13.95::real + 0.00000000000001;
*) The reason it doesn't fit is that the floating point
representation is using base 2, instead of base 10.
**) The exact value could vary, depending on the floating point
implementation of your system. This is what my implementation does.
