On Wed, Dec 28, 2016 at 9:41 AM, Marc Fromm <Marc.Fromm@xxxxxxx> wrote:
I’m using postgresql9.2. When I export some data using phppgadmin some decimal values are exported as 9.4700003 instead of 9.47 (they show as 9.47 in phppgadmin and when displayed on the web. Others export as 9.5299997 instead of 9.53 (again they show as 9.53 in phppgadmin and when displayed on the web).
The data type for the field is set as type “real.” Is this data type causing the problem and I should change it to decimal?
What could be creating this plus or minus 0.0000003 to the recorded value?
Thanks
Marc
"The data types real and double precision are inexact, variable-precision numeric types. In practice, these types are usually implementations of IEEE Standard 754 for Binary Floating-Point Arithmetic (single and double precision, respectively), to the extent that the underlying processor, operating system, and compiler support it.
Inexact means that some values cannot be converted exactly to the internal format and are stored as approximations, so that storing and retrieving a value might show slight discrepancies. Managing these errors and how they propagate through calculations is the subject of an entire branch of mathematics and computer science and will not be discussed here..."
See also:
https://www.youtube.com/watch?v=PZRI1IfStY0
Cheers,
Steve
