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 

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
> --
> //

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