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Comment by pushpop | Hacker News Reader

In my experience most of the time a field is nullable it’s by accident. Some RDBMS and/or SQL “IDEs” default to allowing null too, which doesn’t help matters. Personally I think NULL shouldn’t be supported unless the developer categorically sets a “yes, I actually do want this archaic option enabled” flag in their DB backend.

Edit: getting a lot of heat for this comment from people misunderstanding it. I’m not saying “null” shouldn’t exist, just that it shouldn’t be the default. Side point: most of the time people think they need null they don’t.

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Nullable is being set by accident? Nullable values are an “archaic” option?

Nullable is different than empty. Consider a contrived example where I’ve extended a user table to include a new column “fullName”. By making this a nullable column, I can determine that a user has not set this value. But maybe the user sets it to an empty string. The API might want to know this and handle it differently — prompting for a value if it’s null, but ignoring “” as “this is what the user wanted to set”.

Without nullable values, I would have to create bit values in a lot of tables indicating if the value was ever set.

Another example is time stamps. Databases have timestamps for createdAt and updatedAt often. There are people who set updatedAt when they set createdAt, but there are people who don’t. I’m in the later camp. If an object was created but never updated, I want to be able to know that. How would I do this if the updatedAt column is not nullable? I’d either have to set a bit field that it has been updated, which feels suboptimal, or I could set it to something like “time.Empty{}”, which is a magic number tied to the programming language? There are plenty of other solutions here, sure, but what’s wrong with nullable fields?

First example: why would you want to handle null and a zero length string differently in that case? That seems a little contrived to me because in both instances the user has elected not to enter that information.

Re your timestamp example, just compare if created is the same as updated. That’s a really easy problem to solve. Though I have seen other scenarios when a timestamp needed to by nullable so I agree there will be edge cases.

I agree that null does have its uses (it’s basically essential for outer joins) but most of the time people think they need null they don’t actually need it. Plus it frequently it causes hidden faults, so it’s usually best to avoid allowing nullable fields unless you’re sure there isn’t any other easy way.

Regarding timestamp, I often have a soft delete timestamp 'deletedAt' in which it must have a null default value. I think this is a perfectly acceptable usecase of db null values

It is though I’d be more tempted to have that as it’s own table with more data attached such as the UID who deleted it, reason (if application supported that), etc. That way you can have more detail on “deleted” records without having to null several fields nor increase your table size for your main table with lots of “deleted” metadata when typically records wouldn’t be marked as “deleted”.

Though “deleted” isn’t really the right term here either because you’re not really deleting data, just removing it from view.

The tool referenced here is for go, a programming language that has pointers. Pointers can be nil too, which is useful for many of the same reasons that null database columns are useful. There is a difference between uninitialized, initialized with default values, and a custom value.

You may not have this use case you in your application, but I do. I have real scenarios that need to know if a value is initialized or not. I agree that I could solve this in other ways, but nullable columns just aren’t an archaic database option just because you can implement the same behavior in the application code or by rewriting the SQL query.

I’ve had a great deal of experience with Go and there are many who’d argue that nil pointers in there is a mistake as well (though I’ve personally never had an issue - but I do write pretty robust tests too).

I have ran into some instances when I have needed nullable fields in relational databases as well. I’m not claiming null shouldn’t exist. My point was that they should be an opt in rather than opt out because they cause more problems than generally they solve.

Yeah, the world would probably be a better place if the default in a column definition was NOT NULL rather than NULL.

That's not really relevant to this discussion, though -- once you do have a nullable column in your schema, it doesn't make sense in the Go layer to pretend you don't.

> That's not really relevant to this discussion, though

It’s tangential but still relevant to the discussion.

> once you do have a nullable column in your schema, it doesn't make sense in the Go layer to pretend you don't.

I agree and never suggested what this Go API was doing did make sense.

“Unset” is an extremely valuable state to be able to check. It’s why we have null/nil in well-designed languages. The zero value of a golang int is not the same as indicating a lack of presence. There are plenty of scenarios where “unset” is a necessary state vs the zero value.

I agree however it is only valuable under specific circumstances while it can frequently create hidden traps. On balance it causes more problems than it solves. Which is why I suggested it should be an optional flag enabled on the backend rather than the default.

Maybe/Option would be better.

NULL is what we've got though. setting columns to not null is leaps ahead of most programming languages anyway.

> On balance it causes more problems than it solves

This is far from clear

Like everything, it depends on your language and framework. But after 30 years of experience writing software in strictly typed languages, I’ve seen lots of people get caught out with nullable fields.

However if you’re main body of experience is Perl (for example) then NULL isn’t ever an issue.

Right, because no Perl developer has ever used SQL

I get Perl isn’t trendy these days but Perl actually has a very robust set of DB libraries and I have worked in several places were it was the preferred language.

Perl has by far the best DB tooling of any of the many languages I’ve worked with. My point was sarcasm as rebuttal to the idea that a Perl developer might not have encountered a null value

Actually I said NULL isn’t an issue in some languages with looser type systems, not that other developers wouldn’t have encountered a NULL before.

Eg Perl doesn’t have a nil type like Go, so variables passed to DBI which are NULL in the returned SQL query will be undef’ed instead. Effectively a bit like NULL but it only causes a problem if your running with strict flags (which you shouldn’t do on production systems anyway for various reasons; but that’s another topic entirely) otherwise that value falls back to the language default of “”/0/false.

With languages like Go you can easily end up with a panic if you’re not careful (where you’re trying to cast a nil interface{}). Which, I’m guessing, is why this Go library being discussed here does it’s own NULL checking.

> Eg Perl doesn’t have a nil type like Go...

That would be Perl 5. Perl 6 does. From https://docs.perl6.org/type/Nil :

"The value Nil may be used to fill a spot where a value would normally go, and in so doing, explicitly indicate that no value is present."

Right, but Perl 6 is also now a different language in its own right.

> With languages like Go you can easily end up with a panic if you’re not careful (where you’re trying to cast a nil interface{})

How is this any different to the runtime error you’d get in Perl if you attempted a method call on an undefined value you’d expected to be an object?

It’s different because the DBI wouldn’t return an object for a nullable table record. Which is what we are specifically talking about. Sure other parts of your code might fail if you’re trying to use a scalar as an object (or such like) but that would consistently fail regardless of nullable types on the database.

So I’m not going to argue that Perl doesn’t also have its own hidden traps (a great many of them in fact) nor that it’s interpretation of OOP isn’t terrible but the scope of this discussion was about nullable types and not anything else you now want to draw into the argument.

I agree that NOT NULL should be the default for columns, unfortunately that ship has sailed.

Assuming that the nullable foreign key problem could be solved, I think that NULL is valuable enough (and not that rare) that it ought to be the database owner's choice whether to allow them or not, as opposed to the superuser (not sure which way you're suggesting).

> I agree that NOT NULL should be the default for columns, unfortunately that ship has sailed.

Not really. Defaults change all the time. I’m not asking for a feature to be removed after all.

I don’t deny the change in any specific RDBMS would have to be carefully considered but I’ve worked on a lot harder projects to make transitions in default behaviours than this would be so it’s certainly doable if the momentum was there. However I doubt enough people care enough (if this thread is anything to go by).

> Assuming that the nullable foreign key problem could be solved

Offhand I can think of a few ways to solve that but I also think it’s one of the instances where NULL makes the most sense

> I think that NULL is valuable enough (and not that rare) that it ought to be the database owner's choice whether to allow them or not, as opposed to the superuser (not sure which way you're suggesting).

I completely agree the DBA should still have the power to enable it. My point was just that columns shouldn’t default to being nullable during a CREATE.

To be honest, this could just as easily be “fixed” in graphical database management tools. That would at least enable seasoned DBAs to utilise NULL while preventing others from some of the pitfalls that nullable fields can introduce in some languages. However I still stand by my point that it’s not really a sane default for the way most people architect databases these days (or even “should” be architecting).

Do you think SQL should have outer joins? Then you need NULL.

Firstly, I’ve never said people shouldn’t have NULL. I said columns should default to be nullable.

Secondly, I’d already given outer joins as an example of why SQL needs to support NULL.

I would be nice that people like yourself bothered to read the comments your reacting to instead of jumping off the deep end (-4 on my original post now and people like yourself are literally just reiterating the same points I’ve been making. It’s insane)

If five people misunderstood your comment (which says nothing about outer joins as I reread it) maybe it is your writing that would need to be clearer.

Maybe but my experience on HN is that there’s sometimes a mentality of “fools never differ” on here. I’ve seen countless correct and/or experienced commenters get downvoted even when the comment is well written.

It’s also worth remembering that five people is still only a very small subset of the hundreds that would have read the comment and did understand/agree but didn’t bother to comment for fear of the wrath of those who have already expressed disagreement. For example I was actually voted up several times before the others commented (as well as a few times since).

So it’s really not worth blaming individuals for the comments of others. The only possible outcome from that is starting another, much stupider, argument.

Only if your developers are inexperienced.

I’m sure you’d love to consider yourself infallible but human error can happen even to the best of us.

However if we’re talking from idealistic perspective then you’d have your own DBAs who would create the DB and write the SQL so your developers just call your (for example) stored procedures like APIs rather than writing their own - often unoptimised - SQL themselves.

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