Significant Digits in Floating Point Datatype
От | Lee Hachadoorian |
---|---|
Тема | Significant Digits in Floating Point Datatype |
Дата | |
Msg-id | 4EC94711.4000007@gmail.com обсуждение исходный текст |
Ответы |
Re: Significant Digits in Floating Point Datatype
Re: Significant Digits in Floating Point Datatype |
Список | pgsql-general |
I would like to store some in a single array some data that is conceptually related, but some of the data is floating point, and some of it is integer. Obviously the integer data *can* be stored as double precision, but I need to know about potential loss of precision. Double precision has "a precision of at least 15 digits." I would assume that that would mean that for double precision, 15 digits of data would be faithfully preserved. But I found a question on the list where a value stored as 955.60 sometimes returns as 955.599999999998. (http://archives.postgresql.org/pgsql-general/2011-08/msg00144.php) If this is the case, what does "a precision of at least [x] digits" actually mean? And can I reliably retrieve the original integer by casting to int (or bigint) if the number of digits in the original integer is less than 15? Regards, --Lee -- Lee Hachadoorian PhD, Earth& Environmental Sciences (Geography) Research Associate, CUNY Center for Urban Research http://freecity.commons.gc.cuny.edu
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