Re: Database normalization

["Bart Degryse" <Bart(dot)Degryse(at)indicator(dot)be>]

<quote>Im using Django as my Object relational Mapper so im pretty sure I can not add a constraint such as ...</quote>

Then you should seriously consider changing your mapper.

>>> "Sebastian Ritter" <ritter(dot)sebastian(at)gmail(dot)com> 2007-08-28 16:37 >>>
Thanks for the information.

Both tables would be exactly sames apart from the  foreign key relation to clients or services. I agree that it seems strange to have one column that is always null. Im using Django as my Object relational Mapper so im pretty sure I can not add a constraint such as : CHECK constraint where !(col1
IS NULL and col2 IS NULL).

Another factor ive been considering is that one of the fields in this table(s) definition(s) is free flowing text which could potentially become very large. Should I take this in to
consideration when deciding whether to split the tables? In terms of searching speed that is.

Kindest regards.
Sebastian

On 8/28/07, Andrew Sullivan <ajs(at)crankycanuck(dot)ca> wrote:

On Tue, Aug 28, 2007 at 12:47:45PM +0100, Sebastian Ritter wrote:
> > The update/message format is exactly the same for both. Should I make two
> > different tables:

> >   one table with extra columns : is_client, client_id, service_id, where
> > either client_id or service_id would be null depending on the is_client
> > boolean?

Is the rest of the data the same?  If so, then one table is right.
If not, then more than one table.  In either case, I really hate the
idea of two columns, one of which is always null.  But if you're
going to do that, make sure you add a CHECK constraint where !(col1
IS NULL and col2 IS NULL).

A

--
Andrew Sullivan  | ajs(at)crankycanuck(dot)ca
I remember when computers were frustrating because they *did* exactly what
you told them to.  That actually seems sort of quaint now.
                --J.D. Baldwin

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