Re: changing a column type

  • From: Tim Gorman <tim@xxxxxxxxx>
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Fri, 01 Jun 2012 16:02:01 -0600

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
--
http://www.freelists.org/webpage/oracle-l


Other related posts: