Re: Anomaly with SUM().

Anthony Best <abest@digitalflex.net> writes:
> I've noticed that the SUM() seems to overflow under some situations.
> The only difference is the order that the data is retrived from the
> database.

> accounting=# select  sum(amount)  from transactions, chart WHERE
> account=chart.id;
>          sum
> ---------------------
> 5.6843418860808e-14
> (1 row)

> accounting=# select  sum(amount)  from transactions, chart WHERE
> account=chart.id AND amount=amount;
> sum
> -----
>    0
> (1 row)

That's not an overflow, it's merely roundoff error.  If this surprises
you, possibly you should be using type NUMERIC instead of float.

            regards, tom lane