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Nulls Nullified (2005)

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Re: Nulls Nullified (2005)

#31

Post by dtech »

classified wrote: post #23
quickthrower2 wrote: post #2

NULL makes little sense from first principles. Either get rid of it, or allow nulls (and logically any other union) by supporting union types. It is quite arbitrary to allow a type that makes sense (string, int) etc. and then also allow nulls so you allow INT | NULL union but no other unions. So you have this multi-purpose "other value" whose meaning is inferred by the application. I guess they were added as a pragma…

It's not a union type, but an option. INT | NULL --> Option .

Option is an union type

Re: Nulls Nullified (2005)

#32

Post by HideousKojima »

cubefox wrote: post #12
MrJohz wrote: post #8

Earlier quoted context omitted.

Typescript does have full unions, although only partially discriminated ones (in the sense that `number | string` is discriminated but `number | number` is not - custom discriminators can be written fairly easily though). This resolves the problem that the previous poster had - nullability is not some magic trait of certain types, but rather a function of the general case of union types. In that case, `string | null`…

What does being "discriminated" mean here?

https://en.m.wikipedia.org/wiki/Disjoint_union

Re: Nulls Nullified (2005)

#33

Post by petalmind »

quickthrower2 wrote: post #2

NULL makes little sense from first principles. Either get rid of it, or allow nulls (and logically any other union) by supporting union types. It is quite arbitrary to allow a type that makes sense (string, int) etc. and then also allow nulls so you allow INT | NULL union but no other unions. So you have this multi-purpose "other value" whose meaning is inferred by the application. I guess they were added as a pragma…

> For example not everyone has a middle name, but you don't want to go all 5th Normal Form on it.

(actual question) how does 5NF apply here?

I thought that this case could be handled null-free by introducing a separate table

people_middlenames (human_id PK, middlename NOT NULL);

Is it already 5NF? I thought 5NF requires more complex structure of data, like explained in Wikipedia, for example.

Thanks,

Re: Nulls Nullified (2005)

#34

Post by AnimalMuppet »

sacado2 wrote: post #21
quickthrower2 wrote: post #2

NULL makes little sense from first principles. Either get rid of it, or allow nulls (and logically any other union) by supporting union types. It is quite arbitrary to allow a type that makes sense (string, int) etc. and then also allow nulls so you allow INT | NULL union but no other unions. So you have this multi-purpose "other value" whose meaning is inferred by the application. I guess they were added as a pragma…

In theory NULL (or any such sentinel value, such as the infamous NaN is floatin-point arithmetic) makes sense because there are partially defined functions. Division being the most famous example, but most basic operations on lists share that property too. The problem is the way it's handled in many programming languages, where it can blend so easily with legitimate value and blow the whole program off at execution t…

I could argue that { number that is defined | number that is not defined } is in fact a union type (or, perhaps more correctly, a sum type).

Re: Nulls Nullified (2005)

#37

Post by VMG »

bazoom42 wrote: post #30
dspillett wrote: post #26

Earlier quoted context omitted.

Worse: with JSON NULL is considered a type not a value of other types, which can make validating nullable values with JSON-Schema a royal pain.

JSON does not define a type system, but javascript defines null as the only value of the null type. This works fine in eg typescript since you can use a type union of null and any other type, if you want to indicate a nullable value.

but don't forget that `typeof null === 'object'` :)

Re: Nulls Nullified (2005)

#38

Post by bruce343434 »

sacado2 wrote: post #21
quickthrower2 wrote: post #2

NULL makes little sense from first principles. Either get rid of it, or allow nulls (and logically any other union) by supporting union types. It is quite arbitrary to allow a type that makes sense (string, int) etc. and then also allow nulls so you allow INT | NULL union but no other unions. So you have this multi-purpose "other value" whose meaning is inferred by the application. I guess they were added as a pragma…

In theory NULL (or any such sentinel value, such as the infamous NaN is floatin-point arithmetic) makes sense because there are partially defined functions. Division being the most famous example, but most basic operations on lists share that property too. The problem is the way it's handled in many programming languages, where it can blend so easily with legitimate value and blow the whole program off at execution t…

Being pedantic here but "sentinel" means "signalling the end of a sequence" (such as a 0 byte for C strings, or visually when you close an array or a block of code with `}`)

Re: Nulls Nullified (2005)

#39

Post by marcosdumay »

dspillett wrote: post #24
cubefox wrote: post #10

The author talks a lot about how NULL in SQL is supposedly unnecessary, and claims that it is totally possible to handle unknown SQL values without NULL. Yet he successfully avoids explaining how his solution is supposed to work. At the end he links to a (paid?) paper where his solution is apparently explained, though the link has since ceased to work. Great.

There are many papers describing how NULL as an explicit “value” (you still at least need something to present empty results from left or right joins) can be made unnecessary – just look back to the development of relational databases and the theory that are based upon. No need to pay for this author's paper when it probably just restates things that are found in many open access papers/books/other. Representing unkn…

It's not a problem with the theory, because the theory was not created to be a high-performance application.

It's also clearly not a problem with SQL since people very loudly and clearly prefer the version with nulls and operations that create nulls.

It is a problem with the idea that people should program in relational algebra. They shouldn't. It's the same kind of issue as functional languages that extend lambda calculus; logical languages with explicit evaluation strategies; type systems with undecidable situations; module systems that allows access to private features... No actual usable system is a perfect representation of the math behind it.

Re: Nulls Nullified (2005)

#40

Post by cactusfrog »

Null means unknown. I think the main issue is that people use it to mean “not applicable to this row”, which is different than null’s initial purpose. I think the problems with null could be solved by adding in another None value to distinguish between these two situations.
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