RE: Counterquestion - is Oracle a He or a She - or an It or a hermaphrodite

-----Original Message-----
From: Leandro Guimaraes Faria C. Dutra [mailto:ldutra_at_toyota.com.br] Sent: Monday, August 08, 2005 8:21 AM
To: Kennedy, Jim
Cc: Niall Litchfield; oracle-l_at_freelists.org; oracle-l-bounce_at_freelists.org; psinger1_at_chartermi.net Subject: RE: Counterquestion - is Oracle a He or a She - or an It or a hermaphrodite

oracle-l-bounce_at_freelists.org 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
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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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