You get what you ask for, Ibrahim. Floating point numbers (e.g. double
precision) are good for measuring things, it doesn't matter whether the
length of a line is 1.57 metres or 1.5699999999999 metres. Field1
doesn't have the exact value 79.69, it has a value of approximately
79.69 (e.g. 79.69000000000000001238) and similar for Field2.

If such differences do matter, you should probably use fixed point
numbers - e.g. decimal or numeric.

HTH,
Set

ibrahim bulut wrote:

>
> i am in trouble double precision field with subtract operation
>
> field1 is double precision
> field2 is double precision
>
> field1's value is 79.69
> field2's value is 78.12
>
> when i subtract field2 from field1 with this sql statement
>
> select field1 - field2 from table1
>
> the result is 1,56999999999999
>
> the result must be 1,57
>
> what is the problem
>
> ibrahim bulut
> software and database expert
> iletisim online ltd.sti.
> turkish republic