Re: changing a column type

From: Tim Gorman <tim_at_evdbt.com>
Date: Fri, 01 Jun 2012 16:02:01 -0600
Message-ID: <4FC93BD9.1040000_at_evdbt.com>

Yes, modified BCD, but in Oracle's case, it is one base-100 digit per byte. In the BCD of yore, it was one decimal digit per nibble (i.e. 4 bits); works out to roughly the same thing from a storage perspective.

So, each Oracle NUMBER datatype starts with the exponent (one byte) and then all remaining bytes are used to express the significant digits in base-100.

Memory is kind of hazy, but I recall teaching this for the "Oracle8 Internals" seminars back in the 1998-2000 timeframe...

On 6/1/2012 3:50 PM, Hans Forbrich wrote:
> Yes, both number and date store each digit individually, two to a byte,
> in modified Binary Coded Decimal. Sort-a tells you when the design was
> locked in. If you remember BCD ... :-)
>
> /Hans
>
> On 01/06/2012 2:46 PM, Gints Plivna wrote:
>> Most probably because the internal representation of Number datatype is
>> muuuuuuuch different than that of char and varchar2. You can get some
>> insight for example here
>> http://www.ixora.com.au/notes/number_representation.htm
> --
> http://www.freelists.org/webpage/oracle-l

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Received on Fri Jun 01 2012 - 17:02:01 CDT