RE: Counterquestion - is Oracle a He or a She - or an It or a hermaphrodite
- From: "Kennedy, Jim" <jim_kennedy@xxxxxxxxxx>
- To: "Leandro Guimaraes Faria C. Dutra" <ldutra@xxxxxxxxxxxxx>
- Date: Mon, 8 Aug 2005 08:29:28 -0700
-----Original Message-----
From: Leandro Guimaraes Faria C. Dutra [mailto:ldutra@xxxxxxxxxxxxx]
Sent: Monday, August 08, 2005 8:21 AM
To: Kennedy, Jim
Cc: Niall Litchfield; oracle-l@xxxxxxxxxxxxx; oracle-l-bounce@xxxxxxxxxxxxx;
psinger1@xxxxxxxxxxxxx
Subject: RE: Counterquestion - is Oracle a He or a She - or an It or a
hermaphrodite
oracle-l-bounce@xxxxxxxxxxxxx gravou em 2005-08-08 12:20:02:
> So your DB is context-dependent. NULLs attack.
NULLs are ambiguous, their interpretation depend on context. If
SQL allowed us to define special values, we'd have a better solution, as
currently exist in Tutorial D (only implemented in a toy DBMS, Rel) and D4
(Alphora Dataphor).
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Leandro Guimarães Faria Corcete DUTRA
Administrador de Bases de Dados +55 (11) 4390 5383
Toyota do Brasil Ltda ldutra@xxxxxxxxxxxxx
São Bernardo do Campo, SP BRASIL
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No, NULLS mean no data. My example made a lot of sense, we don't have any data
on whether the patient has any allergies or not. Why don't we have any data?
We never asked the question. We can not medically assume he does or does not
have allergies. Sure there is "context" in the sence that the column is
designated as the FK into the allergy table and not the FK into the medication
table. For medications a similar statement could be made. NULL for the
foreign key into the meds table means We don't know if he is taking medication
or not.
Jim
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