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Re: How much storage numeric vs. number(2)

From: Thomas Kyte <tkyte_at_us.oracle.com>
Date: Wed, 13 May 1998 23:02:04 GMT
Message-ID: <355e25d0.17874392@192.86.155.100>


A copy of this was sent to Kevin Barnes <kbarnes_at_airmail.net> (if that email address didn't require changing) On Wed, 13 May 1998 13:14:47 -0500, you wrote:

>How much storage difference is there between defining a column numeric
>vs. numeric (X).
>
>I find that restricting the length of the field in most cases causes
>more development pains than allowing unrestricted lengths.
>
>TIA,
>
>Kevin

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
Herndon VA  

http://govt.us.oracle.com/ -- downloadable utilities  



Opinions are mine and do not necessarily reflect those of Oracle Corporation  

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 Wed May 13 1998 - 18:02:04 CDT

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