Re: What does this NULL mean?
- From: "Alfredo Novoa" <alfredo_novoa@xxxxxxxxxxx>
- Date: 12 Dec 2005 07:03:24 -0800
Eric Junkermann ha escrito:
> The number of long threads about NULLs indicates that they are a source
> of difficulty and disagreement.
Nulls are a big source of problems. I have found and corrected hundreds
of bugs caused by nulls in a single application, and this is quite
irritating.
> ... If my Manager points to a NULL in a report, I don't say 'That is a
> NULL.' I say something like 'That customer is retired, and does not
> have a work address' or 'The user left that field blank.' That is if I
> am familiar with the data. If I am unfamiliar then the NULL tells me
> nothing, I can only shrug my shoulders and say 'Sorry, I don't know.'
A report must not have nulls.
I have never seen a null in a report, only blank spaces.
> The best way to look at a NULL is as a sort of denormalisation.
I think that the best way to look at a null is as a sort of corruption
or a botch-up. Relations and nulls are incompatible.
On the other hand, denormalization is a sort of flawed database design.
> If we
> have a table X {A, B, C} where A is the key, B is a column we are not
> currently interested in, and C is the column which is NULL in at least
> one row, then we are really talking about two tables X1 {A, B} and Y {A,
> C}, where at least one row in X1 does not have a corresponding row in Y.
Indeed, nulls are nothing but a dirty botch-up to improve performance
with primitive database systems.
Regards
.
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