| Oracle FAQ | Your Portal to the Oracle Knowledge Grid | |
 |
 | |||
| Oracle FAQ | Your Portal to the Oracle Knowledge Grid | |
|
| |||
Home -> Community -> Usenet -> c.d.o.server -> Re: Number Size on NT
On Tue, 6 Jan 1998 14:43:42 -0500, "Josh Blatt" <jblatt_at_harvard.edu> wrote:
>We have several tables where some number fields are set to way too high.
>I'm wondering how much I should worry about sizing them precisely. How does
>Oracle store these? Is there a performance hit to having variables too
>large? If so, and where are the break points?
>
>Thanks much,
>
>Josh
>jblatt_at_harvard.edu
>
Server concepts manual, chapter 6, section on "Number Datatype" includes this (and much more) about the number datatype:
<quote>
Oracle stores numeric data in variable–length format. Each value is
stored in scientific notation, with one byte used to store the exponent
and up to 20 bytes to store the mantissa. (However, there are only 38
digits of precision.) Oracle does not store leading and trailing zeros. For
example, the number 412 is stored in a format similar to 4.12 x 10^2,
with one byte used to store the exponent (2) and two bytes used to
store the three significant digits of the mantissa (4, 1, 2).
<quote>
So, the number 412 in a number(3) or a number(38) will consume the same exact amount of storage. Storage wise -- setting the scale and precision is not meaningful. Application wise -- setting the scale and precision is very meaningful. Fix the numbers not for the storage but for the fact that a number(3) is just that -- a number with 3 digits of precision. Consider the scale and precision to be constraints, they can edit your data.
Thomas Kyte
tkyte_at_us.oracle.com
Oracle Government
Bethesda MD
http://govt.us.oracle.com/ -- downloadable utilities
Anti-Anti Spam Msg: if you want an answer emailed to you, you have to make it easy to get email to you. Any bounced email will be treated the same way i treat SPAM-- I delete it. Received on Tue Jan 06 1998 - 00:00:00 CST
 |
 |