Hi, I have received the following email from a colleague, and am quite
frankly baffled by the idea.

I am just wondering if anyone has any advice or suggestions about
this????

=== BEGIN MAIL ===
The DB2 DBA has requested that all columns in the tables be defined as
not null with default to improve storage, performance, and ease of
backup/recovery. Currently there are several columns in each table
that are nullable. By making these columns not null with default,
there would always be a value in the column, space for char/varchar,
and 0 for integer/smallint/decimal. Does this cause any problems with
the Java/Hibernate code? The DBA has indicated that all of the other
Java applications are defined this way.
=== END MAIL ===

Thanks,
John.

DaFrizzler wrote:

NULL is NULL. If your application uses NULL (or, better said, doesn't
specify values), then NULL is what should be used.

NULLable columns aren't a performance problem if your data has NULLs.
In fact, they are a performance *improvement*. Where NULLable columns
are a performance hit is when the data is (almost) never NULL.

Pulling a column value out of the database and checking it to see if it
is some magic value ('' or 0 or -1 or 'NULL' or whatever) is
substantially worse than checking the NULL flag. It is a fallacy that
nullable columns are a performance hit; it is only a (minor)
performance hit when the NULL flag is always the same value (if always
FALSE then the check is a waste; if always TRUE then the column is a
waste).

DaFrizzler wrote:
I agree with greg. what is that DBA smoking? NULL is not a performance
or storage issue in DB2. And if it affects his backup/recovery, that
DBA needs to be replaced. This thinking sounds like an old mainframe
flat file programmer talking.


OH! I see what the real purpose is in the last sentence: "all the
other..."
That DBA is not thinking, he is just doing monkey see monkey do. Tell
him to document the reasons, including pointing to IBM manuals or
bulletins that support this view. I'm sure the request will quickly
fade away. (I'll not be surprised to hear the DBA is a new hire or
recent promotion.

Ed

On 23 Jan 2007 08:52:21 -0800, "Ed Prochak" <edprochak (AT) gmail (DOT) com>
wrote:

Harsh.

But fair.

Lemming
--
Curiosity *may* have killed Schrodinger's cat.

Ed Prochak wrote:
Lemming wrote:
One hopes this DBA is an imminent terminee.

- Lew