Frank Swarbrick wrote:

> My DBA says that a column defined, for instance, as DECIMAL(11,2) and
> containing a value of 1.00 takes up no more space on the database
> disk than a column defined as DECIMAL(7,2) and containing a value of
> 1.00.
>
> I am honestly having a hard time believing this, but I don't know
> where I can find the answer.
> Help?
>
> Thanks,
> Frank

Your DBA is indeed mistaken (assuming he's referring to DB2 :-). From
the CREATE TABLE reference in the DB2 9.5 InfoCenter [1] (search for
the "Storage Byte Counts" heading):

"Storage Byte Counts: The following table contains the storage byte
counts of columns by data type for data values. The byte counts depend
on whether or not VALUE COMPRESSION is active. When VALUE COMPRESSION
is not active, the byte counts also depend on whether or not the column
is nullable. The values in the table represent the amount of storage
(in bytes) that is used to store the value.

....

DECIMAL (when VALUE COMPRESSION is not active and the column is not
nullable): The integral part of (p/2)+1, where p is the precision"

So a DECIMAL(11,2) NOT NULL column without VALUE COMPRESSION requires 6
bytes, while a DECIMAL(7,2) column with the same attributes requires 4
bytes per row, regardless of the value stored within the row.

[1]http://publib.boulder.ibm.com/infocenter/db2luw/v9r5/topic/com.ibm.db
2.luw.sql.ref.doc/doc/r0000927.html


Cheers,

Dave.