I finally made an account just to respond to this, I hope you don't find that too aggressive a move.
Null is a perfectly valid value for data, and should be treated as such. A default value (e.g. -1 for a Boolean or an empty for a string) can make your system appear to work where NULL would introduce a runtime error, but that doesn't mean your system is performing as expected, it just makes it quieter.
I know it's tempting to brush NULL under the rug, but nothing is just as valid a state for data as something, and systems should be written generally to accommodate this.
I agree with you re: NULL being a useful thing. I personally use nullable floats in an internal company program to denote unknown values. However, the "billion-dollar mistake" everyone brings up with it has to do with NULL allowance being implicit. In languages like C/C++, Java, C#[a] (and more), any pointer could be NULL and the only way to know is to do a NULL check. In SQL (which we're talking about here), one must explicitly call out `NOT NULL` in the column's definition.[b] Rust (and other FP languages) gets a point here by having "optional" types one must use to have a NULL-like system.
[a]: C# is fixing this with "nullable reference types", but as long as it's still opt-in, it's not perfect (backwards compatibility and everything). I can still forcibly pass a NULL to a function (defined to not take a null value) with the null-forgiving operator: `null!`. This means library code still needs `ArgumentNullException.ThrowIfNull(arg)` guards everywhere, just in case the caller is stupid. One could argue this is the caller shooting themselves in the foot like `Option.unwrap_unchecked` in Rust, but "good practice" in C# (depending on who you ask) tends to dictate guard checks.
[b]: Which is kind of stupid, IMO. Why should `my_column BOOL` be able to be null in the first place? Nullable pointers I can understand, but implicitly nullable everything is a horrible idea.
In SQL as you've said, nullability is explicit. It's arguably the wrong way around (i.e. NOT NULL rather than NULLABLE), but it is explicit. I feel the issue comes from the intersection of languages without explicit nullability and their data storage techs; removing that explicit typing from SQL doesn't fix the issue.
(I feel you agree with this btw, just being explicit)
Comments
I finally made an account just to respond to this, I hope you don't find that too aggressive a move.
Null is a perfectly valid value for data, and should be treated as such. A default value (e.g. -1 for a Boolean or an empty for a string) can make your system appear to work where NULL would introduce a runtime error, but that doesn't mean your system is performing as expected, it just makes it quieter.
I know it's tempting to brush NULL under the rug, but nothing is just as valid a state for data as something, and systems should be written generally to accommodate this.
I agree with you re: NULL being a useful thing. I personally use nullable floats in an internal company program to denote unknown values. However, the "billion-dollar mistake" everyone brings up with it has to do with NULL allowance being implicit. In languages like C/C++, Java, C#[a] (and more), any pointer could be NULL and the only way to know is to do a NULL check. In SQL (which we're talking about here), one must explicitly call out `NOT NULL` in the column's definition.[b] Rust (and other FP languages) gets a point here by having "optional" types one must use to have a NULL-like system.
[a]: C# is fixing this with "nullable reference types", but as long as it's still opt-in, it's not perfect (backwards compatibility and everything). I can still forcibly pass a NULL to a function (defined to not take a null value) with the null-forgiving operator: `null!`. This means library code still needs `ArgumentNullException.ThrowIfNull(arg)` guards everywhere, just in case the caller is stupid. One could argue this is the caller shooting themselves in the foot like `Option.unwrap_unchecked` in Rust, but "good practice" in C# (depending on who you ask) tends to dictate guard checks.
[b]: Which is kind of stupid, IMO. Why should `my_column BOOL` be able to be null in the first place? Nullable pointers I can understand, but implicitly nullable everything is a horrible idea.
In SQL as you've said, nullability is explicit. It's arguably the wrong way around (i.e. NOT NULL rather than NULLABLE), but it is explicit. I feel the issue comes from the intersection of languages without explicit nullability and their data storage techs; removing that explicit typing from SQL doesn't fix the issue.
(I feel you agree with this btw, just being explicit)