Re: Null's vs Empty string

From: Eric Palmer <efp_at_etechinc.com>
Date: 1996/11/02
Message-ID: <327b33fd.697272_at_news.mindspring.com>#1/1

On Sat, 2 Nov 1996 05:05:44 GMT, herman_at_iquest.net wrote:

>Dick van Oordt <dvoordt_at_pi.net> wrote:
>
 

>
>You should be aware that any numeric columns which are left NULL are
>not considered to be zero in Oracle. You should ALWAYS use the NVL
>function on numeric columns when doing any type of math. Example:
>
>select
> num_col_1 + num_col_2
>from
> sometable;
>
>will not give the expected answer if either column is NULL. You
>should always write this as:
>
>select
> NVL(num_col_1,0) + NVL(num_col_2,0)
>from
> sometable;
>
>to make sure that a zero is added to num_col_1 if num_col_2 is NULL.

I disagree. There are many cases where you want the numeric value to be left as NULL. You should only NVL convert to a 0 value if it makes sense for the type of data you have.

Consider patient blood chemistry - a column for white cell count. A missing value (NULL) is much different than a value of 0.

Nulls are here for a purpose. Ypu sure don't want to calc. an average value and include missing values as 0. It would be statistically incorrect.

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Eric F. Palmer
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http://www.etechinc.com/ *** Standard Disclaimer ***

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Received on Sat Nov 02 1996 - 00:00:00 CET