thanks Ann,
You're right, the best option seems to be decimal (18,18).
(19,19) doesn't work :
SQL error code = -842. Precision must be from 1 to 18

--- In firebird-support@yahoogroups.com, Ann Harrison <aharrison@...> wrote:
>
> On Thu, Feb 2, 2012 at 6:50 AM, angel_ignacio_colmenares
> <angel_ignacio_colmenares@...> wrote:
> > I'm writing a firebird provider for ServiceStack.OrmLite and unit tests
> > ask for store  the value : 0.686956521739130434782 in a table.
> > the datatable is simple:
> >
> > CREATE TABLE TEST
> > (
> >    v1 float,
> >    v2 float
> > );
>
>
> Float is a useless datatype, having only seven digits of decimal
> precision. You'll do better with double - with about 16 decimal
> digits of precision. Even that isn't enough for an accurate
> representation of your number, which needs 21 digits. I think the
> closest you'll come is decimal [19,19]
>
> Ann
>