Steve Jones - Editor (8/30/2010)

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I've always seen "N/A" as "Not applicable", but you give some good other responses that might be used. Hence another point for the "non-nulls" argument.

alen teplitsky (8/30/2010)

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i've seen this no NULL's allowed OCD thing being taken to extremes

say you sign up a customer today and promise some service that will be done in the near future but you're not sure of the date. since the column is not null you have to put in a crazy date like 1/1/2049. or if something was done in the past then 1/1/1901

so if a customer calls in a few days the CSR will happily tell them they can expect to see someone come to their site in 2049

RalphWilson (8/30/2010)

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I have dealt with DBA's who insisted on all columns being non-NULL and I have engaged in "disucssions" about such (both in person and in cyberspace) and I have yet to find a really good argument for changing my position: NULLs should be used when appropriate and avoided when not apporpriate.

If there is a referential integrity rule that, in effect, says that every row in TableA has to have a FK/PK link to TableB, then it is inappropriate for that column in TableA to be NULL. However, if there is a column, for instance, in a Hospital Information System's PatientDetails table, that is supposed to contain a Date of Birth and it is possible that a) that information may notbe readily available (e.g. John Doe is unconscious when admitted) and b) it is not a show stopper if it either is incorrect or unavailable, I would rather have that column in that row left NULL than to assign an arbitrary DOB. If the column is not essential to the overall integrity of that row, when I am faced with the choice of using an arbitrary default value or leaving the column NULL, I choose the NULL.

So, Steve, what is the definition of "N/A"? Is it "Not Applicable" or "Not Available" or "No Answer"?

RonKyle (8/30/2010)

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Just because there are multiple possibilities does not invalidate the use of Nulls.