Re: Warning about null and open question to Oracle

John Jones <john_at_iluvatar.tip.duke.edu> writes:

>I appreciated everyone's response to this, but the majority of responses
>have been to just wrap a nvl around everything. That is ok, but when you
>are comparing around 50 or more columns that is a lot of typing and as a
>programmer I look for ways to cut down on typing as much as possible. I
>just think that NOTHING should be equal to NOTHING. I have heard that
>other databases do this and was really just sounding off hoping Oracle
>would do the same. Oh well, can't have everything I guess. Thanks for
>listening.

The problem, however, is that NULL does not mean "nothing", NULL means "unknown". And if two values are unknown you can't know if they are equal to each other or not. The problem with NULL is that it requires three-valued logic (T, F and ?) and people tend to think in terms of two-valued logic (T and F).

See chapter 8 of Chris Date's "Relational Database Writings 1985-1985" for an interesting discussion of the problems with NULL.

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