At 03:23 2015-04-16, Laurie Alvey <[email protected]> wrote:
In my innocence, I wonder why you want to disallow NULLs? They are, IMHO,
the best way to hold unknown or irrelevant column values.
They get ambiguous. Take your example above. Does a null mean
unknown or irrelevant? The two are different cases. e.g. A
employee's salary might be unknown, or the employee might not be salaried.
You can always record explicitly that something is unknown if you want.
Nulls poison expressions. The moment you have the possibility
of a null, you have to code handle nulls. Yes, the tables may be
less complex, but that complexity then has to be dealt with in the
app code again and again and again.
Due to an error in SQL, summing a column in a table where there
are no matching rows gives a result of null. It should give a result
of 0, that being the identity element for addition. Because of this
one glitch, I have had to adjust results in several places in my
system, replacing null with 0.
Sincerely,
Gene Wirchenko
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