database design

Michael L Torrie torriem at chem.byu.edu
Thu Jun 9 12:42:42 MDT 2005


On Thu, 2005-06-09 at 11:45 -0600, Steve Dibb wrote:
> I'm working on creating a new table in our database, and I'm wondering 
> -- why bother with the possibility of NULL values in a field?  It seems 
> like it always adds more work then its worth.
> 
> What's the benefit of adding the option of IS NULL when you usually have 
> to check to see if its also blank (field = '' OR field IS NULL)?

You've now seen the greatest flaw in SQL databases.  Clearly there are
definitely times that you need NULLs, because of the limitations of SQL
relational theory.  The truth is SQL database really do violate several
laws of relational database theory.  The presence of the NULL really
means that relational algebra isn't quite "pure" in SQL.  This is a
tradeoff that some pundits really harp on.  Of course going to the other
extreme (like XML "databases") has problems too.

I believe that the use of NULLS can be minimized with careful database
normalization.

> 
> Steve
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