Ivan Prenosil wrote:

>> I'm wanting to select items that have a timestamp value that's a
>> certain number of minutes from current_timestamp. E.g., to select
>> items that have some_date within the last 10 minutes, I'm trying
>> something like:
>>
>> select * from foo where some_date - (10.0/(24.0*60.0)) >=
>> current_timestamp
>>
>> This is based on the documentation that says the decimal portion of a
>> number is added as minutes to the timestamp value.
>>
>> Apart from this being a very awkward way to express an interval,
>> there are rounding errors -- e.g. the expression of 10 minutes above
>> appears to behave more like 9 minutes.
>
> It is even less than 9 minutes. It is because you are using
> only three decimal places, which is too few. Better use floating
> values/arithmetic, compare:
>
> SELECT CAST('2000-1-1 0:0' AS TIMESTAMP) + 10.0/(24.0*60.0) FROM
> RDB$DATABASE; ========================
> 2000-01-01 00:08:38.4000
>
> SELECT CAST('2000-1-1 0:0' AS TIMESTAMP) + 10/1440e0 FROM
> RDB$DATABASE; ========================
> 2000-01-01 00:10:00.0000

Ah...very helpful. Thanks for all the replies.

-- Garrett